NETARTS BA) OREGON
Final Technical Report
to the
Environ mental
Protection
Agency
BENTHIC AUTOTROPHY IN
NETARTS BAY, OREGON
In Reference to
EPA Research
E ST U AR E
BIOLOGICAL
P ROCESSES
Jiiiii(
/
\PRocE
Grant No. R806780
(ACRO-
Oregon State University
May I, 1983
ZOSTERA
ALGAL
PRIMARY
PRIMARY
'ROD
PROD1T
7
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O(TRITAL)
/ ss
xposil
PRETIO
BENThIC AUTOTROPHY IN NETARTS BAY, OREGON
Final Report Submitted June 1, 1983, to the
Environmental Protection Agency
200 S.W. 35th Street
Corvallis, OR 97331
Prepared by
C. David Mclntire, Professor
and
Michael W. Davis, Mary E. Kentula, and Mark Whiting
Research Assistants
Department of Botany and Plant Pathology
Oregon State University
Corvallis, OR 97331
in reference to
EPA Research Grant No. R806780 entitled:
"Relationships Between Nutrient Fluxes and
Benthic Plant Processes in Netarts Bay, Oregon
TABLE OF CONTENTS
Introduction
Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Conceptual Framework for the Research
Ecosystem Processes and Process Capacity
ATentative Model of Estuarine Processes
Netarts Bay . . . . . . . ............ . . . ...... . . . .
. .......... . .
. . . .
....... .
...... . . . . . . . .
EPARhodanuLneStudiesofl978andl979 ......
Some Relevant Literature ......... . . . .
........... . . . ....... . . . .
Benthic Microflora ...... . .......... . . . . . . . . . . . . . . . . . . . ......
Zostera and Macroalgae . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . .
Some Relevant Laboratory Studies ...............................
Columbia River Project . . . . . . . . . . . . . . ..... . . . . . . . . . . . . . . . . . . . .
TheAlgaiPrimaryProductionSubsystetu... ...........
Production Dynamics of Sediment-Associated Algae in
Netarts Bay, Oregon . . . . . . . . . . . . . . . ....... . .
Sampling Strategy . ..............
Methods . . . . . . . . . . . . . . . . . . . . . . , . . .
. . . . . . .
. . . . . .
.
. .
. . .
.
. . . . . . . . . .
.
. . . . . . . . . . . .
, ........ . . . . . . . . . .
Primary Production . . . . . . . . . . . . . . . . . . . . . . . ......... . . . . . . .
Biomass
. . . . . a
*
. . . . . . .. . . . . . . . ...... a a .
.
Sediment Properties . . . . ......... . . . . . . .......... . . . . . . . . . .
Physical and Chemical Variables
Data Analysis . . . . . . . . . . . . . . . . . . . . . . . .
Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
.
. . . . . . . . . . ........ . . . .
. . . ....... . . . . . . . . . . . .
Physical Properties . . . . . . . . . . . . . . * . . . . . . . .
Organic Matter . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . .
. . a a . a . . . . .
a . a a . a a
.
Chlorophyll a Concentration . . . . . . . . . . . . . . . . ...... a a a . . .
Primary Production
. . .
. . . . . . . . . . . . . . . . ......... . a . a . . a a a a .
a a
Relationships Among Variables .. .. . ......... ... .. . ..
Interpretation of AutotrophicPatterns .................. .....
Experimental Studies of Estuarine Benthic Algae
Yaquina Bay
. . a a . ...................... . a a a a . . . . . a a . . .......
Methods ................................. .......... .... .......
.
Primary Production . . . . . . . . . . . . . . . . . . . a a a . a . . . . . . . ..... . . a a a
Biomass
.
. . . . a .
Physical Variables * . . . . . . . . . . ......... a . * a a a . a a a a .
a a . . . a a a
. a a a a . . . . . . . . . a a a a . . .
a a . . a a a . . a a a . . . . . . .
Isolation of DiatomAssemblages
Results .. ...... . ............... ....a.... .aaaa.. .a.a..... I..
Experiments withlntact Sediment Cores
Experiments with Isolated Epipelic Diatoms ......
Experiments with Isolated Macroalgae ... ..........
Interpretation of Experiments ...... . . .. a . a ......... . . a a . .......
Effects of Estuarine Infauna on Sediment-Associated Microalgae
Study Site ....... .........
..... .. ............
Methods .......................................
-3-
-Experimental Design
.
Metabolic Activity ..........................................
Chlorophyll a Analysis ......................................
Macrofaunal Abundance .......................................
Statistical Analysis ........................................
Results ....... .................................................
Field Defaunation Experiment ................................
Laboratory Defaunation Experiment ...........................
Interpretation of Defaunation Experiments ......................
The Diatom Flora of Netarts Bay ...................................
Sampling ..... ..................................................
Methods ........ ................................................
Data Analysis ..................................................
Results ........................................................
StructureofEnvironmentalflata .............................
The Diatom Flora ............................................
AutecologyofSelectedTaxa .................................
Community Patterns ..........................................
The Zostera Primary Production Subsystem ............................
Materials and Methods .............................................
DescriptionoflntensiveStudyArea ............................
SelectionofQuadratandSampleSize. ..........................
Measurement of Biomass .........................................
MeasurementofPrimaryProduction ..............................
Short Marking Methbd ........................................
RadjoactiveCarbon(14C) Method .............................
Data Analysis ..................................................
Morphometrics and Autecology of Zostera marina L. in Netarts Bay
Sexual Reproduction .............................................
Vegetative Growth ..............................................
ProductionDynamicsofZostera ....................................
Biomass ...... ..................................................
Primary Production .............................................
Relationship Between Zostera and Epiphytic Assemblages ............
Description of EpiphyticAssemblages ...........................
Biomass .... ....................................................
Production . ....................................................
Components of Variance .........................................
Bioenergetics of the Zostera Primary Production Subsystem .........
Discussion ......... ...............................................
References .... ......................................................
Appendixl...........
INTRODUCTION
This final report was prepared primarily for the information of persons
having the responsibility of judging the merit of research supported by a
grant from the Environmental Protection Agency (EPA No. R806780).
The
research program was initiated September 1, 1979 and the original project and
budget periods extended from this date to August 30, 1981.
Extensions of the
project and budget periods were requested in May, 1981 and again in January,
1982.
These extensions were granted, and the termination date for the project
and budget periods was reset to August 30, 1982.
Although scientists and
other individuals interested in the production dynamics of benthic plants in
estuaries may find this report an informative summary of our work during the
prOject period, it is not intended to be a definitive publication and should
not be evaluated as such.
Instead, five manuscripts representing segments of
the research presented in this report are in preparation for submission to
refereed professional journals.
The primary purpose of the final report is to
integrate the various aspects of the research and to provide an outlet for the
data that can be made available to other scientists.
The general objective of research supported by EPA Grant No. R806780 was
to determine mechanisms that control the production dynamics of benthic plants
and associated epiphytes in Netarts Bay relative to physical processes and
changing patterns of nutrient distribution.
In particular, we were especially
concerned with biological processes that were related to the patterns of
nutrient flux determined by the EPA dye studies of August, 1978 and January,
1979.
These studies involved the introduction of Rhodamine dye and subsequent
-5-
comparisons of the dye concentration with concentrations of substances of
interest at selected stations in the estuary.
Nutrients of interest included
dissolved organic carbon (DOC), particulate organic carbon (POC), nitratenitrate (NO2-NO3), orthophosphorous (Ortho-P), ammonia nitrogen (NH3), and
molybdate reactive silica (Si); in addition, temperature, salinity, turbidity,
fluorescence at 460 nm and 660 nm, and Rhodamine concentrations also were
monitored,
The results of the EPA investigation suggested that nutrient
dynamics were strongly related to biological processes associated with large
areas of seagrass (Zostera marina) during August; but in January, corresponding patterns were more closely related to physical processes.
Therefore, our
general objective stated above was compatible with the EPA's research program
at Netarts Bay and provided the basis for a detailed examination of benthic
plant processes in the estuary.
For research purposes, it was convenient to partition our work on benthic
plant processes in Netarts Bay into two subsystems:
tion and Algal Primary Production.
Zostera Primary Produc-
These subsystems are part of a tentative
conceptual model of the entire estuarine ecosystem, the details of which are
described in the next section of this report.
The research approach involved
an intensive field investigation of the two subsystems during a two-year
period and some concurrent experimental work on the Algal Primary Production
subsystem.
The sampling strategy in the field was carefully designed to take
advantage of the existing knowledge of nutrient distribution and circulation
in the estuary.
This report is organized into three major subsections:
Background, The
Algal Primary Production Subsystem, and The Zostera Primary Production
Subsystem.
In the Background section, we present a conceptual framework for
the research, briefly describe the estuary, review the EPA dye studies of 1978
and 1979, and present a review of relevant literature.
The Algal Primary
Production Subsystem section is concerned with the production dynamics of
benthic micro and macroalgae relative to sediment properties and other
physical and biological variables.
In this section, we also present the
results of laboratory studies designed to establish functional relationships
between algal primary production and selected physical and biological
factors.
The Zostera Primary Production Subsystem section presents the
ecological energetics of a seagrass population and associated epiphytic and
benthic microalgae.
Also, information concerning plant morphometrics and
subterranean detritus is included in this section.
BACKGROUND
I.
Conceptual Framework for the Research
Ecosystem Processes and Process Capacily
The ecological literature often refers to various physical and biological
processes in contexts that are usually intuitively understandable without a
formal, theoretically structure.
However, for analytical purposes, it is
desirable to formalize the process concept by definitions and the establish
ment of a system for diagramming relationships.
Here, the definitions apply
only to biological processes, and physical processes are treated conceptually
as driving or control functions.
Definition:
A process is a systematic series of actions relevant to the
dynamics of the system as it is conceptualized (or modelled).
-7-
The process concept is made more explicit by the diagram illustrated in
Figure 1.
This structure is compatible with both autotrophic and hetero-
trophic processes (e.g., algal primary production and deposit feeding).
In
the figure, a process, the entire contents of the circle is elaborated into
one state variable, the process capacity, and six variables representing
inputs and outputs associated with the process.
Theoretically, process
capacity includes two components, a quantitative aspect which is the biomass
at any instant of time involved in the process, and a qualitative aspect which
relates to taxononiic composition and physiological state.
Other variables
associated with the process include resource input, cost of processing (C),
waste discharge (W), losses to the process of decomposition (B), losses to the
process of predation or grazing (P or C), and export (E).
In the diagram,
decomposition, predation, and export act directly on the process biomass and
are represented by dashed arrows from the state variable box.
In contrast,
resource input, cost of processing, and waste discharge are associated with
the process as a whole and are, therefore, represented by solid arrows connected to the perimeter of the circle.
At this point, the concept of process capacity needs further clarification.
Relative to a given set of inputs, the potential performance of a
unit of biomass associated with a process such as primary production (or
deposit feeding) may change with temporal and spatial changes in the taxonomic
composition and physiological state of that biomass.
Or, stated from a popu-
lation perspective, one combination of populations or parts of populations
involved in a particular process may do things at different rates, i.e., may
require a different parameterization than a different combination involved in
the same process.
Theoretically, process capacity expresses both quantitative
-P
RESOURCE
INPUT
C
w
COMPONENTS OF PROCESS CAPACITY:
1. QUANTITATIVE: biomass
2. QUALITATIVE: genetic information
OTHER VARIABLES:
C is COST OF PROCESSING
W is WASTE DISCHARGE
B is LOSS TO DECOMPOSITION
P is LOSS TO PREDATION
E is EXPORT
Figure 1.
Schematic representation of the process concept illustrating
a state variable,, the process capacity, and relevant input
and output variables.
and qualitative aspects of the process state and, therefore, represents a unit
that is time and spatially invariant relative to its relationships with other
components of the system.
The problem is to develop a set of rules that will
map process biomass, a variable that changes qualitatively, into process
capacity, a corresponding variable that maintains a constant functional potential.
As yet, we have not invented an approach to the direct estimation of
process capacity, and most current models represent only the quantitative
aspects (biomass) of process capacity.
In this report, we deal with quali-
tative differences by partitioning the biomass associated with the process of
primary production into several state variables (e.g., micro-algae, species of
macroalgae, and seagrass).
The process viewpoint emphasizes the capacity of a system or subsystem to
process inputs and the mechanisms that control and regulate that capacity.
Ideally, parameter estimation is based on direct measurement of processes in
the field or laboratory rather than on the summation of activities of individual species populations.
Moreover, the process approach is particularly
suitable for the investigation of benthic autotrophy in estuaries, as field
and laboratory methods are available to monitor primary production in complex
assemblages of mlcroalgae, without having to measure photosynthetic rates of
the many constituent taxa.
A Tentative Model of Estuarine Processes
A tentative conceptual model of an estuarine ecosystem is illustrated in
Figures 2-5.
This preliminary model provided the structure that was necessary
to design a research strategy consistent with our project objectives.
Since
ecosystem modelling is an iterative process, this structure undoubtedly will
change as more field and laboratory studies generate new information.
-10-
Estuarine biological processes can be considered holistically in terms of
inputs and outputs relative to the entire ecosystem (Fig. 2).
Also, the eco-
system can be investigated mechanistically, in this case as a system of three
coupled subsystems that can be uncoupled and investigated holistically or
mechanistically in isolation after coupling variables have been carefully
identifed.
This conceptualization of ecosystem processes is based on the FLEX
modelling paradigm developed by W. S. Overton (1972, 1975, 1979) and related
to the general systems theory of Klir (1969).
For our purposes, it is conven-
ient to partition estuarine biological processes into Water Column Processes,
Emergent (or Marsh) Plant Processes, and Mudflat (or Benthic) Processes.
This
report is primarily concerned with the dynamics of Mudflat Processes, and in
particular with the Primary Food Processes subsystem of Mudflat Processes.
A hierarchical arrangement of the subsystems of Mudflat Processes is
illustrated in Figures 3 and 4.
This conceptual model partitions Mudflat
Processes into two coupled subsystems:
consumption.
Primary Food Processes and Macro-
Since our research was concerned with benthic autotrophy
associated with estuarine tidal flats, the Primary Food Processes subsystem
was the subsystem of interest and was partitioned conceptually into some of
its subsystems.
On the other hand, Macroconsumption includes such subsystems
as Suspension Feeding, Deposit Feeding, and Predation (Fig. 2), processes not
elaborated in Figures 3 and 4.
Primary Food Processes has three subsystems:
Zostera Primary Production, Algal Primary Production, and Detrital Decomposition.
Zostera Primary Production consists of Macrophyte Primary Production-
and Epiphyte Primary Production (Fig. 3), two subsystems
intensive study site in Netarts Bay.
investigated at an
Some variables associated with the Algal
-11-
EMERG8
PLANT
ESTUARINE
WATER-
BIOLOGICAL
COLUMN
PROCESSES
ZOST ERA
PRIMAR''
ALGAL
PRIMAR'(
DETRITAL
Figure 2.
MUD FLAT
PROC ESSES
SUSPENSIcN\
FEEDING )
DEPOSIT
FEEDING
PR EDAT ION
Systems diagram of Estuarine Biological Processes and
associated subsystems.
-12-
MUDFLAT
PROCESS ES
PFP: PRIMARY FOOD PROCESSES
MC = MACROCONSUMPTION
APP= ALGAL PRIMARY PRODUCTION
ZPP ZOSTERA PRIMARY PRODUCTION
DD = DETRITAL DECOMPOSITION
Figure 3.
MPP= MACROPHYTE
PRIMARY
PRODUCTION
EPP= EPIPHYTE
PRODUCTION
Systems diagram of Mudflat Processes indicating details of
the Zostera Primary Production subsystem.
-13-
Primary Production subsystem are diagramed in Figures 4 and 5.
In Figure 4,
primary production is controlled directly by nutrient input, light energy
input, respiratory losses, and a complex of other physical processes that have
effects on photosynthesis and respiration.
In addition, losses or gains of
algal biomass (the process state variable) by the mechanisms of animal consumption, export, transfer to detrital processes, or imports also affect
process dynamics.
As mentioned earlier, capacity for algal primary production is affected
by both the biomass and the qualitative aspects of that biomass.
In the
research at Netarts Bay, the qualitative aspects were considered by expressing
algal biomass as several state variables.
For example, preliminary research
indicated that three functional groups of algae are important primary producers on the tidal flats of the bay.
Figure 5 represents the process of
algal primary production in more detail.
In this case, algal biomass is
partitioned into three state variables: microalgae (the diatom flora and less
prominant inicroalgae), the Enteromorpha
Ulva flora, and the less abundant
red and brown macroalgae (e.g., Gracilaria verrucosa).
ated with the Enteromorpha
Process rates associ-
Ulva are considerably higher than rates found for
other functional groups, but this group is only conspicuous during several
months in the summer.
Therefore, the sampling strategy and experimental pro-
cedures for investigating algal primary production were adjusted Co
accommodate temporal, qualitative changes in the process state variable.
The structure illustrated in Figure 5 served as the conceputal basis for
the research described in the Algal Primary Production subsystem section.
This diagram illustrates the variables that must be examined in order to
-14-
MUDFLAT
PROCESSES
MC
PFP
APP
ZPP
E
DD
BIOMASS
PF
--o---
0
L
N
R
PFP = PRIMARY FOOD PROCESSES
MC= MACROCONSUMPTION
DD= DETRITAL DECOMPOSITION
ZPP ZOSTERA PRIMARY PRODUCTION
APP=ALGAL PRIMARY PRODUCTION
Figure 4.
PF PHYSICAL FACTORS
L LIGHT
N
NUTRIENTS
Ra RESPIRATION
C
CONSUMPTION
1= IMPORT
E
EXPORT
Systems diagram of Mudflat Processes indicating details of
the Algal Primary Production subsystem.
-15-
ALGAL PRIMARY PRODUCTION
LIGHT
ENERGY
MICROALGAE
PHYSICAL
FACTORS
ESPIRATION
ENTEROMORPHA
ULVA
GRACI LARIA
NUTRI ENTS
GRAZING
EXPORT''
DETRITAL
DECOMPOSITION
Figure 5.
The Algal Primary Production subsystem and associated state
variables with relevant inputs and outputs.
-16-
understand the dynamics of this subsystem within the coupling structure of the
entire estuarine ecosystem.
A similar approach was taken for the examination
of the Zostera Primary Production subsystem.
In summary, Algal Primary Pro-
duction and Zostera Primary Production were the target subsystems for the
research presented in this report; and the results of this research were
interpreted relative to the EPA dye studies of 1978 and 1979 and within a
coupling structure for the entire ecosystem.
II.
Netarts Bay
Netarts Bay is the sixth largest estuary in Oregon with a surface area of
941 hectares of which 612 hectares are classified as tideland area (Fig. 6).
The permanently submerged land is small in area (ca. 329 hectares) and is
restricted to a relatively narrow channel extending from the mouth of estuary
to the mudflat at the south end.
Netarts Bay drains an area of only 36.3 km2
and is partially exposed to waves at the throat.
The depression which the
estuary now occupies was formed as a consequence of the differential erosion
of the soft sedimentary rock (the Astoria Formation) between the basalt headlands of Cape Meares and Cape Lookout during the Late Tertiary Period.
The
sand spit which separates the bay from the Pacific Ocean is a remnant of three
sand dunes which have eroded as a consequence of sea level elevation after the
last period of glaciation.
Because of the lack of any major tributaries, the
estuary exhibits a relatively high salinity with values usually above 30 0/00
and seldom below 14 0/00 at any location.
Although Burt and McAllister (1959)
reported that the bay remained vertically well-mixed throughout the year, the
recent dye studies by the EPA indicate that horizontal mixing is more complex
-17-
NETARTS BA)' OREGON
j
Figure 6.
Nap of Netarts Bay, indicating the location of the channel
at low tide.
-18-
with only limited mixing occurring between ocean water and bay water during
each tidal cycle.
Sediments introduced into Netarts Bay are estimated to
average only 2,250 tons annually.
III.
EPA Rhodamine Studies of 1978 and 1979
Field studies of nutrient fluxes in Netarts Bay by the EPA and associated
scientists were performed in August, 1978 and January, 1979.
Rhodamine dye
was introduced at a station in the southern part of the estuary at low tide,
and its distribution and concentration was monitored to examine patterns of
circulation and horizontal mixing in the system.
that at low tide the water retained in the channel
In general, it was found
the bay water -- was the
same water that was over the seagrass and mudflat areas during high tide.
As
the tidal cycle moves ocean water into the estuary, the bay water is pushed
out of the channel and over the seagrass areas and tidal flats.
Also, it was
found that relatively little mixing takes place between incoming ocean water
and the resident bay water, as detectable amounts of Rhodamine were found at
low tide ten days after its introduction.
Comparisons of nutrient concentrations at many sampling stations in the
channel and over the seagrass and tidal flats with Rhodamine concentrations
provided a basis for the examination of nutrient fluxes transported by
advection, within the water column, and fluxes between the water column and
the Zostera Primary Production and Algal Primary Production subsystems.
Furthermore, this kind of analysis provides a holistic view of the dynamics of
selected substances that can serve as a basis for the investigation of mechanisms at finer levels of resolution.
-19-
The results of the August study strongly implicated the seagrass and
associated organisms as biological components accounting for significant
deviations of patterns in the concentrations of Si, NO2-NO3, and DOC from the
pattern exhibited by the Rhodamine.
During this time of year, there is evi-
dence that there is a net flux of Si and NO2-NO3 from the water column to the
Zostera Primary Production subsystem and that this net uptake is operating on
a time resolution greater than one tidal cycle but less than the time resolu-
tions associated with advection or water column processes.
Apparently there
is a rapid net flux of ammonia from the Zostera Primary production and Algal
Primary Production subsystems to the water column on a time resolution of less
than one tidal cycle.
However, this substance is more patchy in distribution
than Si or NO2-NO3, indicating detectable changes within the water column.
DOC exhibited a net flux from the bottom to the water column and was apparently exchanged on a time resolution similar to that of Si and NO2-NO3.
The
spatial and temporal pattern of temperature during the summer study followed
the pattern of Rhodamine and clearly provided a contrast between bay water and
ocean water.
At this time, the bay maintained a temperature near 20°C while
the ocean water was approximately 9°C.
During the period between the summer and winter studies, there was a
massive export of plant biomass out of the grass beds; and by January the
grass consisted of roots, rhizomes, and short remnants of leaf and stem
tissue.
Nutrient data from the winter study indicated that patterns were
controlled primarily by physical processes, and NO2-NO3 and DOC fluxes between
the bottom and the water column were operating on a relatively long time
resolution (perhaps several weeks).
A net flux of Si to the bottom was not
-20
detected, and this substance was actually introduced into the water column
from some of the small tributaries.
Interpretation of the dye and nutrient studies suggested that pronounced
nutrient gradients of biological significance develop during the growing
season and extend from the channel along circulation transects over the sea
grass and mudflats as ocean water moves back into the channel on an incoming
tide.
A detailed study of vertical and horizontal nutrient profiles along
such a transect was investigated by Nancy Engst of the EPA in collaboration
with Dr. Jorg Imberger and the P1.
A float study was undertaken to determine
the pattern of circulation over the seagrass, and a suitable transect for
sampling was selected from the results of these preliminary observations.
This research is scheduled for completion by late spring or summer, 1983 and
will provide a more mechanistic view of the pattern and quantity of nutrient
exchange between the benthos and the water column.
IV.
Some Relevant Literature
The following review of literature represents an arbitrary selection
of references that provide a good basis for comparing the results of this
study with other research being conducted by the Principal Investigator
and associates and with the results of studies by other scientists.
More
specifically, the review covers selected field studies of tidal flat
primary production and some past laboratory work on benthic autotrophy.
Benthic Microflora
Relatively little information is available on rates of primary production
and respiration in assemblages of marine and estuarine benthic microalgae.
-21-
Methodology employed in the estimation of these rates usually involves the
isolation of a sample in a flask, bell jar, or chamber and the subsequent
monitoring of carbon-14 uptake or changes in the concentration of metabolic
gases in the medium (e.g., see Bott et al. 1978; Darley et al., 1976; Hall et
al., 1979; Hunding and Hargrave, 1973; Marshall etal., 1973; Mclntire and
Wuiff, 1969; Pamatmat, 1965, 1968, 1977; Pomeroy, 1959; Van Raalte etal.,
1974).
Such methods attempt to estimate the productivity of the entire algal
assemblage and require certain assumptions that are usually violated to some
degree depending on the particular situation.
The difficulty in partitioning
primary production among the constituents of the benthic microflora is one of
the most complex problems in aquatic ecology.
Steele and Baird (1968)
described a method for measuring carbon assimilation by epipsammic organisms,
and the method of Hickman (1969) is designed to separate epipelic and
epipsammic algae for measurements of primary production.
To our knowledge,
there is still no satisfactory field method for partitioning community
respiration into bacterial and producer respiration in assemblages of
microorganisms.
The study by Steele and Baird (1968) indicated that rates of primary pro-
duction on beach sand were relatively low, in the range of 4-9 g C m2 yr'.
There was an increase in chlorophyll a and organic carbon with depth below the
low-water level to 13 m, but decreases in light intensity with depth apparently accounted for a corresponding decrease in the ratio of
concentration of chlorophyll a.
uptake to the
In any case, organic carbon content under
1 m2 of beach sand to a depth of 20 cm was about 50 g.
Furthermore, viable
populations of diatoms were found to a depth of 20 cm at the low-water
-22-
stations.
This distribution of living organisms was attributed to mixing of
the sand by wave action and stimulated speculation concerning metabolic rates
of diatoms buried below the zone of effective light penetration for extended
periods.
Dye (1978) compared rates of epibenthic algal production on sand
with the rates measured on mud in a South African estuary (the Swartkops
estuary).
The mean rate of primary production in estuarine sand (53 g C m2
yr) was higher than that found for shifting beach sand by Steele and Baird
but less than half of the mean rate found for the muddy areas (116.5 g C nr2
yr).
Other estimates of total primary production for assemblages of benthic
microorganisms associated with sandy silt or mixtures of silt and clay are
higher than those reported above for epipsammic assemblages alone.
Gr$ntved
(1960) investigated the productivity of the microbenthos in some Danish fjords
and estimated that the average carbon fixation was 116 g C m2 yr'.
He also
found that average fixation was 142 mg C m2 (2 hrY' for 87 samples from
sand (mean water depth of 0.85 m) and 139 mg C n12 (2 hrY
from sandy silt (mean depth of 1.11 m).
for 42 samples
After correcting the data for depth
effects, it appeared that primary production was greater when the bottom
material contained silt and ciay than when the substrate was 'pure' sand.
Moreover, maximum primary production was at water depths between 0.5 and
0.7 m, and rates at one locality (Naeraa Strand) for the period from November
to February were about one-third of the rates found for the rest of the years
In another study, Gr$ntved (1962) found that photosynthetic potential was
about four times higher on the exposed tidal flats in the Danish Wadden Sea
than in the Danish fjords.
More recent work in the Western Wadden Sea (Cadee
-23-
and Flegeman, 1974) indicated that mean annual primary production of the micro-
flora associated with tidal flats was about 100 g C
m2 yr. Primary produc-
tion was correlated with temperature, solar radiation, and functional chloro-
phyll; and excretion was only 1% of the annual primary production.
Further
studies (Cadee and Hegeman, 1977) indicated that primary production was
related to the tidal level of the stations, and annual rates varied from 29 g
c m2 on the lowest tidal flat station to 188 g C if2 at the highest station.
The investigation of benthic primary production in the Eems-Dollard estuary
and the Eastern Dutch Wadden Sea by Colijn (1974) indicated a seasonal
periodicity in bioniass and production consisting of a spring maximum and a
lower maximum in the autumn; winter values were low, and summer values were
intermediate between spring and winter values.
Colijn and van Buurt (1975)
found that the photosynthetic rate of marine benthic diatoms in the field was
saturated by a light intensity of approximately 10,000 lux, and at higher
intensities no photoinhibition was found.
Within a range of 4° to 20°C the
photosynthetic rate increased about 10% per degree C.
Gross primary production of microalgae in the intertidal marshes on the
coast of Georgia was measured by the oxygen method with bell jars (Pomeroy,
1959).
The annual rate of gross production was estimated to be 200 g C if2;
efficiency of photosynthesis ranged from 1 to 3% at light intensities less
than 100 kcal m2 hr
kcal m2 hr'.
and was 0.1% or less at intensities in excess of 300
Pamatamat (1968) using similar methods found that the primary
production on an intertidal sandflat on False Bay, San Juan Island was
comparable to the Danish Wadden Sea and the salt marshes of Georgia.
In this
case, photosynthetic efficiency over the year averaged 0.10, 0.11, and 0.12%
-24-
of total incident radiation at the three stations under investigation.
Also,
rates of photosynthesis exhibited an endogenous rhythm apparently related to
tidal cycle; rates were relatively high during flood and ebb tide and
depressed during low and high water.
Marshall etal. (1971) investigated
primary production of the benthic microflora of shoal estuarine environments
in southern New England and concluded that an annual rate of about 100 g C
m2 yr1 is representative of both the Danish and southern New England shoals.
In contrast, Leach (1970) reported a value of only 31 g C m2 yr
for an
estuarine intertidal mudflat in northeast Scotland and suggested that the
relatively low value for this region might be related to climatic factors.
The relative contribution of microalgal assemblages to the total primary
production in marine and estuarine ecosystems has been examined in various
field studies.
Gallagher and Daiber (1974) investigated primary production of
edaphic algal communities in a Delaware salt marsh and found that the annual
rate varied from 38 to 99 g C m2, depending on the local composition of the
associated macrophyte flora.
Gross algal production was about one-third of
the angiosperm net production, and the highest rates occurred when the angiosperms were dormant.
Sources of autotrophic and allochthonous organic carbon
available to the Nanaimo Estuary delta, British Columbia, were investigated by
Naiman and Sibert (1979).
Annually, benthic microalgae produced 4-55 g C
phytoplankton about 7.5 g C m2, macroalgae 0.9-7.5 g C m2, Zostera marina
26.9 g C m2, and Carex 564 g C in2.
The angiosperms entered the food web as
detritus, and allochthonous sources of carbon (dissolved and particulate
organic matter) from the river contributed over 2000 g C m2 yr'.
Joint
(1978) measured rates of primary production on the sediment surface and in the
-25--
water column along the coast of England.
The annual primary production was
143 g C m2 for the sediment and 81.7 g C m2 for the water column.
Primary
production on the sediment surface ceased when the mudflat was flooded by the
Burkholderetal. (1965) found that daily rates of primary production
tide.
(carbon-14 method) for different functional groups of benthic microalgae
averaged 4.45 mg C rr12 (blue-green algae), 4.05 mg C m2 (diatoms) and 5.03 mg
(mixed flagellates and diatoms) during some studies in Long Island
C m
Sound.
In the Chukchi Sea near Barrow, Alaska, the primary productivity of
the benthic microflora ranged from below 0.5 mg C m2 hr
in winter when the
sampling area was covered with ice to nearly 57.0 mg C m2 hr' in August
(Matheke and Homer, 1974).
The latter value was eight times the productivity
of the ice algae and twice that of the phytoplankton.
Taylor and Gebelein (1966) investigated the vertical distribution of
plant pigments in intertidal sediments at Barnstable Harbor, Massachusetts.
Highest concentrations of all pigments occurred in the upper 1 mm.
Chloro-
phyll a and c and fucoxanthin concentrations decreased with depth and were
20 and 50% of surface values at 5 cm; diatoxanthin, diadinoxanthin, and
carotene concentrations did not decrease with depth.
In a related study,
Taylor (1964) showed that 10% of the solar radiation penetrated to a depth of
1.5 mm in sand with a grain size between 63 and 177 -'m in diameter; 1% reached
a depth of 3 I'm.
Microalgae living on sediment in this area required only
12 g cal cm2 hr' to obtain their maximum photosynthetic rate and were able
to photosynthesize at 90% of their maximum rate at a depth of 2 mm at noon on
a clear day.
Riznyk and Phinney (1972) also investigated the vertical distri-
bution of chorophyll a and primary production in the intertidal sediments of
Southbeach and Sally's Bend in Yaquina Estuary, Oregon.
The sandy silt of
Southbeach had an estimated annual gross primary production of 275 to 325 g C
m2
yr, while the finer silt of Sally's Bend had estimated values of 0 to
125 g C m2 yr. These differences were attributed to the presence of large
populations of bacteria and meiofauna in the fine, detritus-rich sediment of
Sally's Bend.
The greatest biomass of microalgae on both tidal flats was
found in the upper 1 cm of sediment, but viable diatoms were found throughout
the length of the piston core sampler (9.1 cm in length).
Chlorophyll a at
Southbeach ranged from a mean concentration of 9.3 hg cm3 at a depth of 7.89.1 cm to 20.7 hg cm3 in the upper 1.3 cm; corresponding concentrations at
Sally's Bend were 2.9 and 4,7 jig cni3, respectively.
Summarizing the primary production studies cited above, we can say that
annual rates of gross primary production by niicroalgae on tidal flats fre'-
quently fall between 50 and 200 g C m2 yr', and values for the epipsammic
assemblages associated with shifting beach sands may be as low as 10 g C n12
yr
or less.
Microalgae and plant pigments usually are concentrated in the
upper few millimeters of sediment, but living cells are often found at depths
of 20 cm or more.
Vertical distribution apparently is related to the extent
to which the sediment is mixed by water movements, although epipelic diatoms
can exhibit a vertical migration in the upper few millimeters.
There is some
indirect evidence that primary production and the development of assemblages
of autotrophic organisms may be inhibited to some extent when there is a large
amount of organic detritus in the sediments.
Bacterial activity in such sedi-
ments reduces the oxygen concentrations, alters the pH, and perhaps generates
compounds that are toxic to some microalgae.
-27-
Zostera and Macroalgae
Rates of net primary production of eelgrass populations reported in the
literature vary considerably.
m2 yr
Representative values expressed as g dry weight
are 10 to 58 (Massachusetts
holder and Doheny, 1968), 273 to 648 (Alaska
McRoy, 1966), 24 to 842 (Cali-
fornia - Keller, 1963), 187 to 1078 (Puget Sound, Washington
1972), and 304 (Netarts Bay, Oregon
Burk-
Conover, 1958), 765 (New York
Stout, 1976).
Phillips,
Examples of biomass esti-
mates for eelgrass during the growing season expressed as g dry weight
are 186 to 324 (Alaska
m2
McRoy, 1966), 6 to 421 (California - Keller, 1963;
Waddel, 1964), 5 to 29 (Massachusetts
Conover, 1958), 148 to 2470 (New
York - Burkholder and Doheny, 1968), 18 to 396 (Puget Sound, Washington
Phillips, 1972), and 288 to 467 (Netarts Bay, Oregon
Stout, 1976).
Until
the study described in this report, Stout's investigation of the Zostera
population of Netarts Bay was the only published report of an eelgrass study
in an Oregon Estuary.
In addition to the production and biomass values
reported above, she found that (1) the populations could be partitioned into
shallow-water and deep-water eelgrass; (2) shallow-water and deep-water eelgrass averaged 671 shoots m2 and 1056 shoots m2, respectively; (3) the
percentages of biomass in roots and rhizomes were 46% (shallow-water plants)
and 29% (deep-water plants); and (4) the percentage of reproductive shoots
were 17% (shallow-water plants) and 21% (deep-water plants).
Zostera marina has also been investigated relative to its biogeography
(McRoy, 1968), energy flow to consumers (Thayer etal., 1972), nitrogen
fixation (Goering, 1974), and its associated animal populations (Kikuchi and
Peres, 1973).
Here, we are particularly interested in the studies of nutrient
-28-
dynamics and the epiphytic flora.
McRoy and Barsdate (1970) found that eel-
grass absorbs phosphate through both roots and leaves and that the plant at
times may pump phosphate from the sediments back into the wate
column.
Up-
take of phosphate was greatest in the light, but it also occurred in the dark.
Additional work by McRoy, etal. (1972) indicated that rates of uptake and
excretion of phosphorus by both roots and leaves of eelgrass are dependent on
the orthophosphate concentration in the medium.
abosrbed 166 mg P m2 day
and excreted 62 mg m2 day
In these studies, eelgrass
from the sediments, assimilated 104 mg
back into the water column.
n12 da1,
The nitrogen-fixing
capacity of three species of seagrasses and associated organisms was investigated by McRoy, Goering, and Chaney (1973).
Rates of fixation of Zostera,
Thalassia, and Syringodium were low or undetectable, and it was concluded that
the process is unimportant in at least some seagrass systems.
These results
were in contrast to the relatively high rates of fixation reported for Zostera
marina by Patriquin and Knowles (1972) and for some other wetland plants of
Oregon by Tjepkenia and Evans (1976).
McRoy (1974) found that epiphyte pro-
ductivity was closely related to that of its host plant (Zoster marina in this
case).
NO3,
NH4+, and (NH2)2C0 were all absorbed by the root-rhizome system
and transported to all parts of the plant, and there was a direct transfer of
both carbon and nitrogen from Zostera to the epiphytes on the leaves.
Penhale
(1977) found that average net primary production was 0.9 g C m2 day
for
eelgrass and 0.2 g C m2 day
for its epiphytes.
Furthermore, it has been
reported that epiphytes can reduce the rate of photosynthesis of eelgrass by
as much as 45% and that this effect is influenced by light intensity and HCO3
concentration (Sand-Jensen, 1977).
Penhale and Smith (1977) also found that
-29-
heavily epiphytized Zostera excreted only 0.9% of its photosynthate and that
excretion was much less in the dark than in the light; excretion increased
after desiccation.
Relative to ecosystem bioenergetics the importance of macroalgae in
Oregon estuaries is greatest in systems having rocky areas, particularly long
jetties (e.g., Yaquina Estuary).
In estuaries without such areas (e.g.,
Netarts Bay), species diversity is low, and the macroalgal biomass is usually
dominated by species of Enteromoropha, Gracilaria, Fucus, and some of the
smaller forms (e.g., Ectocarpus and Polysiphonia).
Complete species lists
along with notes on distribution are available for Yaquina Estuary (Kjeldsen,
1967) and Netarts Bay (Stout, 1976), and Phinney (1977) has published a
comprehensive list of the macrophytic marine algae of Oregon.
Effects of
variations of salinity and temperature on the photosynthetic and respiratory
rates of Ulva expansa, Enteromorpha linza, Laminaria saccharina, Sargassum
muticum, Alaria marginata, and Odonthalia floccosa from Yaquina Estuary have
been investigated by Kjeldsen and Phinney (1971).
Some Relevant Laboratory Studies
Mclntire and Wulff (1969) and Wulff and Mclntire (1972) studied the
effects of illumination intensity, exposure period, salinity, and temperature
on the primary productivity of estuarine periphyton in a laboratory model
ecosystem.
3
in
The laboratory system consisted of afiberglassed wooden trough,
long, 76 cm wide, and 80 cm deep, with the bottom graduated in a "stair-
step" manner.
Tidal cycles were simulated by periodically pumping seawater
into the system, and the illumination intensity was regulated by adjusting the
-30-
height of a large lamp fixture over the trough.
A respirometer chamber was
designed to monitor changes in dissolved oxygen concentration in water surrounding a sample community.
Such samples consisted of periphyton assemblages
that developed in the laboratory ecosystem on acrylic plastic plates or other
substrates of interest.
Results of experiments conducted with the laboratory ecosystem indicated
that periphyton biomass accumulated most rapidly on plastic substrates subjected to relatively high illumination intensities without exposure to desiccation.
In the absence of grazing, biomass ranged from 17.2 g m2 on a sub-
strate exposed to the air for 8 hr per day to 128 g m2 on a substrate with no
exposure; corresponding concentrations of chlorophyll a were 0.037 and 0.837 g
m2, respectively.
Primary productivity in periphyton assemblages exposed to
periods of desiccation was less under winter conditions than under correspond-
ing conditions in the summer; and productivity in assemblages not exposed to
desiccation was strongly affected by illumination intensity during both the
summer and winter experiments.
Rates of primary production at 18,500 lux
ranged from about 0.08 to 1.00 g 02 m2 hr
depending on the biomass and
chlorophyll concentration.
Since 1976, Admiraal and associates have reported the outcome of a nunber
of experiments related to the ecology of benthic diatoms in the Eems-Dollard
estuary, a part of the Dutch Wadden Sea (Admiraal 1977 a, b, c, d, e; Admiraal
and Peletier, 1979 a, b; 1980 a, b).
Some of the results of these studies
were:
1.
Cell division rates in unialgal diatom cultures decreased when the
light intensity decreased below 5 E m2 daf1 or when the daily
photoperiods were shorter than 8 hours.
-31-
2.
The cell division rate was proportional to the incubation temperatures
between 4 and 20°C.
3.
Light extinction in the sediment column was of critical importance
with respect to the photosynthetic rate and growth dynamics of natural
sediment inhabiting diatom populations.
4.
The photosynthetic rate of cultures and natural diatom populations
were very high during incubation in media with salinities between
4 0/00 and 60
/oo.
Differences among species were found only at
salinities below 8 0/00
5.
The supply of phosphate and probably the supply of nitrogenous
compounds were not limiting in the regulation of the numbers of
benthic diatoms in the estuary.
6.
Accumulation of oxygen and the depletion of carbon dioxide were
indicated as the cause of retarded growth in dense assemblages of
benthic diatoms.
7.
Continuous discharges of organic wastewater stimulated the formation
of dense assemblages of benthic diatoms, while the associated high
concentrations of ammonia promoted the dominance of two ammonia
tolerant species.
8.
The presence of sulfide near the surface of the intertidal sediment
eliminated certain sulfide sensitive species from the diatom
assemblage.
9.
Six out of ten species of diatoms isolated from the estuary were
capable of heterotophic growth in the dark, and under limiting light
levels, the addition of organic substrates increased the division
rates of these species.
-32-
Jonge (1980) investigated fluctuations in the organic carbon to chlorophyll a ratio for diatom assemblages isolated from the sediments of the Ems
estuary.
Values for this ratio over a 3-year period ranged from 10.2 to
153.9 with yearly averages and standard deviations of 40.3±13.8; 41.2±20.4,
and 61.4 ± 22.0, respectively.
The method of isolation involved the use of
lens tissues and a filtration procedure which produced a suspension of
epipelic diatoms with relatively little contamination by small animals or
bacteria.
This procedure was of particular relevance to our study, as it
provided a living isolated flora of microalgae for estimates of respiration
and for the establishment of a biomass to chlorophyll a ratio.
In a recent paper, Revsbechetal. (1981) compared the results of three
different methods of measuring primary production of sediment-associated
microalgae.
The methods under Investigation were by an oxygen microprofile
using a platinum microelectrode, H'4CO3
exchange method.
fixation, and the standard oxygen
In a highly oxidized sediment, the three methods yielded
almost identical results at low light intensities (20 1-'E m2 sec).
The
oxygen methods underestimated primary production at higher light intensities
when there was conspicuous bubble formation.
Also, the conventional oxygen
method underestimated the primary production in sulfuretum-type sediments as
compared to the other two methods.
HCO
Measurements of the specific activity of
within the photic zone showed a steep gradient of H14CO3
surface.
at the sediment
Calculations of benthic primary production taking the actual
specific activity into account yielded 2 to 5 times higher estimates than
calculations using the specific activity in the overlying water.
-33-
Columbia River Project
This project was initiated by the P.1. in September 1979 as part of the
Columbia River Estuary Data Development Program (CREDDP) and continued until
October 1, 1981.
The general objective of the research was to investigate the
production dynamics of benthic plants on the tidal flats of the Columbia River
Estuary.
In particular, the work was concerned with effects of chemical and
physical gradients on the structural and functional attributes of micro- and
macro-vegetation and on the productivity and biomass of the benthic primary
food supply.
The research plan for the project included (1) a descriptive
field study of the production dynamics of benthic plants on the tidal flats of
the estuary; and (2) an investigation of mechanisms accounting for the
observed dynamics in the field.
Unfortunately, the unanticipated early
termination of CREDDP allowed time and support only for a field investigation
at selective intensive study sites.
However, observational data obtained in
the field provided a good basis for generating hypotheses concerning mechan-
isms that regulate autotrophic processes, hypotheses that were examined in
part by the research described in this report.
Because of the enormous size of the area under investigation by the
Columbia River Estuary Data Development Program (ca., 150 square miles), the
selection of a suitable sampling strategy for the field investigation of benthic autotrophy was a very difficult problem.
approaches were considered:
Essentially, two alternative
(1) a broad survey involving the collection of
non-replicated samples from as many locations as possible over the entire
study area at perhaps two or at most, three different seasons of the year; or
(2) frequent replicated sampling at relatively few intensive study sites.
The
-34-
first approach provides an insight into variation over the largest possible
spatial area but fails to yield information about local variation in space and
time.
The second approach allows the calculation of a variance structure for
each site and gives much more information about temporal variation.
Moreover,
if the intensive study sites are representative of large areas in the estuary,
the second approach can provide considerably more insight into process mech-
anisms than the first approach, particularly if concurrent measurements of
physical variables are obtained along with the biological data.
Data obtained
under the direction of the P.r. were generated from a sampling program based
on the second approach, replicated samples taken at monthly intervals from
five intensive study sites.
A similar approach was used for the field work
described in this report.
Prior to the beginning of the field sampling program in April 1980, the
estuary was surveyed to identify potential sites for intensive study.
Five
sites were selected on the basis of their relative positions along the salinity gradient, their sediment type, and whether or not they were representative
of large, common habitat types in the estuary.
The intensive study sites with
corresponding CREDDP coordinates were Clatsop Spit (3-59-13), Youngs Bay (353-10), Baker Bay (4-0-18), Grays Bay (3-40-17), and Quinns Island (3-29-14).
The sites at Clatsop Spit and Baker Bay were under marine influence, and
surface salinities ranged from 32 0/00 at high tide during low freshwater
discharge to 0 0/oo at low tide during high discharge.
The Clatsop Spit site
was located on the northern side of Clatsop Spit, approximately 1 km west of
Parking Lot D.
This site was characterized by fine sand and relatively high
current velocities.
The Baker Bay site was located on the northern side of
-35-
Baker Bay, near the Liwaco Airfield.
to very fine sand.
The sediment was primarily coarse silt
The site at Youngs Bay was on the western side of the bay,
approximately 1 km south of the mouth of the Skipanon River.
Here, surface
salinities varied from 0 to 10 0/00, grain size of the sediments ranged from
medium silt to fine sand.
Sites in Grays Bay and on Quinns Island were under
strong freshwater influence, with surface salinities always near 0 0/00.
The
Grays Bay site was located on the eastern side of the bay, approximately 1 km
south of the mouth of Crooked Creek.
very fine sand.
the island.
The sediments were composed primarily of
The site at Quinns Island was located on the eastern tip of
Because it was more exposed to river currents than the Grays Bay
site, the sediments were coarser, ranging in grain size from very fine sand to
medium sand.
At each intensive study site, 25-rn horizontal transects were identified
and marked with wooden stakes.
The transects were located in the high, mid,
and low intertidal zones at each station and in the high marsh at all stations
but Clatsop Spit where no marsh exists.
The distance between the upper tran-
sect in the high marsh and the lowest intertidal transect varied from station
to station depending on the slope of the tidal flat.
The transects in the
marsh and in the high, mid, and low intertidal regions were approximately
0.9 m, 0.7 in, 0.5 in, and 0.3 in above mean lower low water, respectively.
Field sampling was designed to generate estimates of primary production
and chlorophyll a concentration in the sediments.
The sampling strategy at
each intensive study site involved the collection of sediment cores for the
analysis of chlorophll a concentration and for measurements of primary production in a respirometer chamber.
Six cores were obtained at random loca-
-36-
tions along each transect, and each of these was subsampled in the laboratory
to obtain estimates of chlorophyll concentration in the upper cm, between
4.5 and 5.5 cm from the surface, and between 9 and 10 cm from the surface.
Concurrently, two sediment cores were obtained from each of the transects in
the marsh and in the upper and lower intertidal regions for measurements of
primary production and oxygen consumption.
These cores were subsampled after
these measurements for estimates of chiorphyll a concentration and organic
matter in the upper centimeter of sediment.
Selected physical variables also
were monitored along with the measurements of primary production and chlorophyll concentration.
The physical variables of interest included temperature,
light intensity, salinity, and five properties of the sediment:
median grain
size, mean grain size, skewness, kurtosis, and the sorting coefficient.
Preliminary results from the analysis of data obtained from April through
October 1980 are summarized below:
1.
Diatoms were the most abundant group of plants on the tidal flats in
the Columbia River Estuary.
Although large numbers of diatom species
were found on each tidal flat under investigation, species composition
varied greatly among tidal flats.
Blue-green algae were frequently
found growing beneath the emergent marsh plants in late summer at all
sites.
Macrophytes were not conspicuous on the estuarine tidal flats.
Zostera marina L. and an unidentified species of Zostera had a patchy
distribution in Baker Bay, and Enteromorpha intestinalis var. maxima
J. Ag., a filamentous green alga, was abundant in marsh samples from
Youngs Bay and Baker Bay in April and May.
A sparse growth of
Potamogeton foliosus Raf. and P. richardsonii (Benn.) Rydb. was
-37-
observed on the tidal flats of Grays Bay during spring and summer,
while Ceratophyllum demersum L. and Elodea canadensis Michx. were
often abundant in marsh pools at Grays Bay.
2.
The highest rates of gross primary production (GPP) were recorded at
the Youngs Bay site.
During the period from May through October, the
mean of all measurements of GPP for Youngs Bay was 108.46 mg of carbon
fixed per square meter per hour at light saturation.
c
2
The mean GPP (mg
hr) was 53.89 at Baker Bay, 35.44 at Quinns Island, 32.36 at
Grays Bay, and 3.00 at Clatsop Spit.
In general, rates of GPP declined in June and July.
This was
particularly evident at the upriver sites of Quinns Island and Grays
Bay.
During this period, increases in scouring and sediment load in
the water column, which were attributed to early summer freshet and
the Mount St. Helens eruption, created an unstable and presumably an
unsuitable habitat for the benthic microflora.
Therefore, rates of
GPP decreased at the lower intertidal levels, which are more exposed
to river flow.
With a decline in freshwater discharge and in the
activity of Mount St. Helens, sediments stabilized and GPP increased
during August and September.
Rates of GPP throughout the estuary
appear to be closely associated with sediment stability; the more
stable the substratum, the higher the rates of GPP.
Production of the benthic microflora in the marsh declined in
spring and early summer as emergent marsh plants began to develop and
shade the sediment surface.
Subsequently, as the emergent vegetation
began to decline in August and September, production of the benthic
microflora began to increase with increasing available light.
3.
Highest concentrations of chlorophyll a in the upper cm of the sediment were generally associated with sites with the greatest rates of
GPP.
Mean concentrations of chlorophyll a (g chl a cm2) in the
upper cm for April through October were 31.77 in Youngs Bay, 23.03 in
Baker Bay, 11.90 in Grays Bay, 10.52 at Quinns Island, and 1.35 at
Clatsop Spit.
Concentrations of chlorophyll a were usually highest in
the marsh and lowest in the lower intertidal zone.
There were no
conspicuous seasonal changes in chlorophyll a concentration at the
intensive study sites.
The highest and lowest monthly mean values
were recorded in April and July, respectively.
In general, it was found that chlorophyll a concentration in the
top cm of sediment was a relatively good predictor of benthic primary
production when the flora was composed of diatoms.
The regression
equation derived from the field data is:
GPP = 2.8955 + 0.3001 CHLOR,
where GPP is the gross primary production expressed as mg C hr
and
CHLOR is the chlorophyll a concentration in the top cm of sediment
expressed as mg.
The corresponding R2 value for this relationship was
0.732, indicating that measurements of chlorophyll a concentration can
serve as a reasonably good tentative estimate of GPP for locations
where direct measurements of primary production are not possible.
This conclusion only applies to assemblages of benthic microalgae in
the intertidal area of the Columbia River estuary, as this relationship is variable in a more marine system such as Netarts Bay (see a
later section of this report).
-39--
4.
The percentage of organic matter in each sediment sample expressed as
ashfree dry weight showed remarkably little variation at each site
during the study period.
There was no apparent increase in organic
matter in the sediments as the emergent plant vegetation began to die
back in late summer and early fall.
In general, highest percentages
of organic matter were associated with sediments in the marsh.
Mean
percentages of ashfree dry weight in sediment samples for April
through October were 4.35 in Baker Bay, 3.26 in Youngs Bay, 2.12 in
Grays Bay, 1.42 at Quirins Island, and 0.42 at Clatsop Spit.
The
higher percentages were associated with the finergrained sediments.
-40-
THE ALGAL PRIMARY PRODUCTION SUBSYSTEM
Studies of algal primary production in Oregon estuaries have been
limited, but some early studies included production measurements made in the
laboratory using intertidal sediment (Riznyk and Phinney, 1972), artificial
substrates (Mclntire and Wulff, 1969; Wuiff and Mclntire, 1972), and macroResults reported here, together with the
algae (Kjeldsen and Phinney, 1971).
recent study in the Columbia River estuary (Amspoker and Mclntire, 1982), are
the first field measurements of algal primary production for sediment-associated communities in Oregon estuaries.
The purpose of the research reported in this section was. to describe
seasonal patterns of algal primary production and associated physical and
biological variables in Netarts Bay.
In addition, experiments were conducted
at the O.S.U. Marine Science Center, Newport, Oregon, to examine mechanisms
that accounted for the patterns observed in the field.
Priorities for the
experimental work were established by the conceptual framework described in an
earlier Section.
Because the research examined autotrophic processes that
occur in many estuaries, the understanding of these processes in Netarts Bay
is relevant to problems that extend beyond the geographical limits of this
particular estuary.
Results of our research on the Algal Primary Production subsystem are
reported in four subsections:
1.
Algae in Netarts Bay, Oregon; II.
Algae; III.
Production Dynamics of Sediment-Associated
Experimental Studies of Estuarine Benthic
Some Effects of Estuarine Infauna on Sediment-Associated Micro-
algae; and IV.
The Diatom Flora of Netarts Bay.
In subsection I, seasonal
patterns of primary production for sediment-associated algae at three inten-
-41-
sive study sites in Netarts Bay are described and interpreted relative to
selected physical variables.
Laboratory studies of estuarine benthic algae
are reported in subsection II.
In particular, these experiments were con-
cerned with the relationship between algal primary production and light
intensity; also, the ratio of chlorophyll a to algal biomass was investigated
in isolated diatom assemblages.
In subsection III, effects of infauna on
algal production dynamics are described from the results of defaunation
experiments in the field and laboratory.
Subsection IV is concerned with the
taxonomic structure of the sediment-associated and epiphytic diatom flora of
Netarts Bay.
I.
Production Dynamics of Sediment-Associated Algae in Netarts Bay, Oregon
This research was concerned with the investigation of seasonal changes in
algal biomass and patterns of algal primary production in Netarts Bay.
Rele-
vant biological variables included microalgal biomass expressed as the chloro-
phyll a concentration in the sediment, the concentration of organic matter in
the sediment expressed as ash-free dry weight, and the rates of gross primary
production and community oxygen uptake as measured in light and dark chambers.
The sampling strategy was consistent with the known dynamics of physical and
chemical processes in Netarts Bay as determined by the EPA Rhodamine studies
(EPA, 1979).
Sampling Strategy
Netarts Bay was surveyed to identify potential sites for intensive study
which were representative of large areas of the bay.
Three sites were
-42--
identified on the basis of sediment type and location in the bay (Fig. 7).
The site near the mouth of the bay was characterized by medium sand (SAND
site); the site along the western shore of the bay had fine sand (FINE SAND
site); and the site along the eastern shore had coarse silt (SILT site).
sites were exposed to moderate wave action.
All
Macroalgae were absent at the
SILT site, and blue-green algae occurred at the mean high water (MHW) level at
the FINE SAND and SILT sites.
At each intensive study site, 50-rn horizontal transects were marked with
wooden stakes.
The transects were located at 0.5, 1.0, 1.5, and 2.0 m above
mean lower low water (MLLW) at each site.
The sampling strategy at each, site
involved the monthly collection of sediment cores for the measurements of
primary production and the concentration of chlorophyll a and organic matter.
On each sampling date, sediment cores were obtained randomly along each transect:
three for measurement of primary production, six for analysis of
chlorophyll a concentration, and three for analysis of organic matter concentration.
Sampling was initiated in March, 1980 and continued for a period
ending in March, 1981.
Cores for the measurement of primary production were
incubated in situ in field respirometers and subsampled after incubation for
the measurement of chlorophyll a concentration in the top cm of sediment.
Cores for the measurement of chlorophyll a concentration and organic matter
content were subsampled in the laboratory to obtain estimates of concentration
in the top cm of sediment and at a depth of 4.0 to 5.0 cm from the surface.
Monthly measurements of physical variables also were made near the transects of all three intensive study sites.
These variables included tempera-
ture, salinity, light intensity of photosynthetically active radiation, and
change in sediment height.
-43-
NE TARTS BAY OREGON
N
P4CIFIc
OREGON
I-
0
1000
METERS
igure 7.
Map of NetartS Bay indicating the location of intensive
(A) the SAND site; (B) the FINE SAND site
study sites:
(C) the SILT site.
and
-44-
Methods
1.
Primary Production
Gross primary production and community oxygen uptake were estimated in
the field from oxygen measurements in stirred, light and dark chambers
designed to hold intact cores of sediment.
Between May and September,
measurements were made in plexiglas chambers which were 92 cm in height, had
an internal diameter of 12.8 cm, and enclosed a sediment surface area of
128.61 cm2 (Fig. 8).
Two light chambers and one dark chamber were used to
estimate primary production at each site.
Each chamber was inserted 30 cm
into the sediment, filled with 5.7 1 of seawater from the bay and sealed.
Water in the chamber was circulated by a magnetic stirrer at a motor speed of
27 rpm.
Rates of oxygen evolution and uptake were based on measurement
periods of 4.0 to 7.5 hours between initial and final readings.
Measurements
of dissolved oxygen were made with an Orbisphere® salinity-corrected dissolved
oxygen system by inserting the oxygen probe into a port on the side of the
chamber.
Between October and March, estimates of primary production were made in
plexiglas chambers which were 14.2 cm in height, had
an internal diameter of
6.8 cm, and enclosed a sediment surface area of 36.32 cm2 (Fig. 9).
Three
replicate chambers were inserted 5 cm into the sediment, withdrawn with intact
sediment cores, and plugged with rubber stoppers.
Each chamber was filled
with 300 ml of seawater from the bay, sealed and placed in a water bath.
Water in the chambers was circulated by a magnetic stirrer at a motor speed of
300 rpm.
Rates of oxygen evolution and uptake were based on measurement
periods of 0.5 to 1.0 hour between initial and final readings.
Readings were
made by replacing the stirrer on top of the chamber with an oxygen probe.
-45-
WATER LEVEL
0-RINC
GASKE7
MOTORBATTERY
UNIT
PORT
MAGNE7
PORT FOR
OXYGEN
0-RING
GASKET
METER PROBE
INCUBATING
MAGNET
MATERIAL
LOWER
COMPARrMENT1
II
II
I
I
II
II
II
II
II
II
II
I
I
I
I
II
II
I
I
II
II
II
I
I
I
I
II
Figure
8.
Diagram of a respirometer designed for the measurement
primary production in a seagrasS communitY.
of
-46-
TURBINE
V
MAGNET
WATER
SOURCE
0-RING SEAL
MAGNET
PORT FOR STIRRER
AND
PROBE
-PORT FOR FILLING
SEAWATER
ALGAE AND
SEDIMENT
RUBBER BUNG
PLEXIGLAS CHAMBER
FOR 02 METABOLISM
Figure 9.
Diagram of a raspirometer designed for the measurement of
benthjc primary productjo in the laboratory.
-47-
Rates of net community production or oxygen uptake were measured when the
chambers were exposed to full sunlight or darkened by covering the water bath
with black plastic, respectively.
Simultaneous incubations of intact sediment in both types of chambers
indicated that chamber type had no significant effect on the rate of primary
production.
All production rates were corrected for seawater-associated
oxygen production in the light, and oxygen uptake in the dark using the light
and dark BOD bottle method for measuring plankton metabolism (Strickland and
Parsons, 1972).
Plankton metabolism was negligible except during August.
Gross primary production was estimated by adding the rate of community
oxygen uptake in the dark to the rate of net community production in the light
for an equivalent period of time.
expressed as mg 02 rn2 h
Estimated rates of gross primary production
were converted to mg C m2 h' while assuming a
photosynthetic quotient of 1.2, i.e., mg C = 0.312 x mg °2
of community oxygen uptake expressed as mg °2
m2 h
m2 h
Estimated rates
were converted to mg C
while assuming a respiratory quoteint of 1.0, i.e., mg C = 0.375 x mg
02 (Westlake, 1965).
2.
Biomass
Microalgal biomass was expressed as the concentration of chlorophyll a in
Samples for chlorophyll a analysis were collected using a 12-cm
the sediment.
long plastic corer with an internal diameter of 2.3 cm.
The corers were
gently pressed 10 cm into the sediment and then were withdrawn carefully with
an intact core.
laboratory.
The cores were capped, frozen, and transported back to the
En the laboratory, the frozen sediment was extruded from the
cores, and sections from the top cm and 4 to 5 cm from the surface were
-48-
excised with a knife.
A core section was placed in a mortar with 0.5 ml of
saturated magnesium carbonate solution and 10 ml of 90% acetone (v/v).
The
slurry was ground with a pestle for one minute, poured into a screw-capped
test tube, and kept in the dark at 4°C for 24 hours.
The extract was centri-
fuged, and chlorophyll a concentration was measured using the method of
Strickland and Parsons (1972).
The Lorenzen equation (corrected for phaeopig-
ments) was used to calculate mg chlorophyll a
These values are uncor-
iti2.
rected for chlorophyllide (Whitney and Darley, 1979).
Macroalgal biomass was sampled by harvesting six replicate 0.25 in2 quadrats randomly along each 50-rn transect.
Samples were rinsed in fresh water,
weighed, dried at 70°C for 48 hours, and reweighed.
Dried samples were ashed
at 450°C for 24 hours and reweighed to determine ash-free dry weight, an estimate of organic matter.
Chlorophyll a concentration in the macroalgae was
determined as described above using approximately 1.0 g wet weight of algae
per sample.
3.
Sediment Properties
Sediment was sampled for organic matter content using the same coring
devise described above for the chlorophyll a samples.
frozen, and transported back to the laboratory.
Samples were collected,
In the laboratory, the frozen
sediment was extruded from the corers and sections from the top cm and 4 to
5 cm from the surface were excised with a knife.
70°C for 48 hours and weighed.
24 hours and reweighed.
Core sections were dried at
These sections then were ashed at 450°C for
A correction for loss of sediment water of hydration
after ashing was determined by adding distilled water to the ashed sediment,
and drying at 90°C for 24 hours and reweighing.
-49-
Bimonthly samples from the top cm of sediment were taken for grain size
Sediment was wet-sieved with a 63 1-'m mesh
analysis (Buchanan and Kain, 1971).
sieve.
The coarse fraction was dried at 70°C for 24 hours and then sieved
through a set of graded sieves to determine fraction weights above 63 1Am.
Fractions below 63 urn were examined by a pipette analysis.
Sediment statis-
tics included mean grain size, the sorting coefficient, arid a measure of skewness (Inman, 1952).
Mean grain size was expressed in phi-units where
-log2 of the grain size in mm.
=
The sorting coefficient expresses the uni-
formity of grain size, i.e., the better sorted sediments exhibit the less
Skewness measures the degree of
uniform distribution of size classes.
symmetry in the grain size distribution, with positive values indicating
skewness to the smaller grain size and negative values indicating skewness to
the larger grain size.
4.
Physical and Chemical Variables
Light intensity was measured in iE m2 sec
radiation with a Licor® quantum meter.
photosynthetically active
Bimetal or thermistor probes were used
to measure temperature, while salinity was measured with a temperature-compensated AO Goldberg® refractometer.
Samples for analysis of nitrite-nitrate
(NO2-NO3), ammonia (NH4), orthophosphate (PO4) and molybdate-reactive silica
(S102) were taken July, August, and September from water in the respirometer
chambers before and after incubation.
These samples were analyzed by methods
for autoanalysis of nutrients (Strickland and Parsons, 1972).
5.
Data Analysis
The chlorophyll and production data were analyzed by a three-way analysis
of variance (ANOVA) with sediment type, tidal height, and time treated as main
-50-
effects; the three-way interaction mean square was used as the error term in
calculating F-values.
All statistical analyses were performed with a Control
Data Corporation Cyber 170/720 computer at the Oregon State University
Computing Center using the SPSS system (Nie et al., 1975) and the REGRESS
subsystem of SIPS (Rowe and Brenne, 1981).
Results
1.
Physical Properties
Sediment characteristics were determined for the intensive study sites
(the SAND, FINE SAND, and SILT sites in Fig. 7) from March, 1980 to March,
1981 in Netarts Bay.
Mean grain sizes in phi-units () were 2.28 at the SAND
site, 2.66 at the FINE SAND site, and 3.79 at the SILT site (Table 1).
Mean
values for the sorting coefficient were 0.34 (well-sorted) at the SAND site,
0.64 at the FINE SAND site, and 1.13 (poorly-sorted) at the SILT site; while
corresponding mean skewness values were 0.25, 0.10, and -0.04, respectively.
In summary, sediment at the SAND site was medium to fine sand, wellsorted, with the most positive skew; sediment at the FINE SAND site was fine
to very fine sand, with medium sorting and a positive skew; and sediment at
the SILT site was very fine sand to coarse silt, poorly sorted and with very
little skew.
Monthly change in sediment height was measured at the three intensive
study sites from April to October (Fig. 10).
There was little net change in
sediment height, except at the SAND site at 1.0 m above MLLW and at the FINE
SAND site at 2.0 in, and 0.5 in above MLLW.
Monthly changes in sediment level
usually ranged from 0 cm to 3 cm, changes that could account for burial or
-51-
Table 1.
Results of sediment grain size analysis for samples obtained every
two months from March 1980, to March 1981, at intensive study sites.
Tidal level is above E.LW; 0.5 m (1), 1.0 m (2), 1.5 bi (3), and
Mean grain size (MEAN) is in phi-units, and sorting
2.0 m (4).
Statistics were
(SORT) and skewness (SKEW) are dimensionless.
Values
are
annual means ()
calculated according to Inman (1953).
of n replicates and the standard error of the mean (SE).
EAN
Site
Level
SAND
All
FINE SAND
SILT
SKEW
SORT
SE
SE
SE
23
2.28
0.03
0.34
0.25
0.43
1
5
2.28
0.10
0.31
1.25
1.25
2
6
2.27
0.03
0.36
0.47
1.20
3
6
2.22
0.05
0.33
-0.54
0.50
4
6
2.34
0.03
0.35
0.00
0.01
21
2.66
0.10
0.64
0.10
0.65
1
3
3.04
0.35
0.70
-0.05
0.22
2
6
2.64
0.14
0.61
0.15
0.11
3
6
2.52
0.25
0.64
0.06
0.07
4
6
2.64
0.13
0.65
0.17
0.08
23
3.79
0.11
1.13
-0.04
0.17
1
5
4.03
0.09
1.24
0.10
0.03
2
6
3.95
0.13
1.00
-0.54
0.61
3
6
3.78
0.34
1.08
0.01
0.08
4
6
3.44
0.19
1.20
0.29
0.07
All
All
FIgure 10.
0
A
M
J
MONTH
J
A
S
.
0
I
I
a
tlonthlv changes in sediment height at intensive study sites in.Netartn flay.
include SANI) (solid circle), FINE/SAND (triangle), and SILT (open circle).
-5.0
I
I
I
z
0.5 N + MLLW
I
C)
g
1
z
I
10
hi
(9
ON + MLLW
I
I
(I)
I
hi
a
a.
___
hi
I
I.5M + MLLW
I
+YiO
I
I
J +5Ø
Ml
>
hi
I
I
I
d -5.0
I
I-
I
I
I
I
I
I
I
I
I
0
I
I
I
ML
I
I
+5.0
-
Sites
U'
-53-
export of surface chlorophyll a and organic matter at certain times and sites.
The SILT site was the most stable site with respect to change in sediment
level during the measurement period.
Temperatures of the air, exposed sediment, and water were usually greater
than 10°C (Fig. 11).
Air, exposed sediment, and water temperature ranges were
from 0°C to 24°C, from 2°C to 19°C, and from 8°C to 18°C, respectively.
Photosynthetically active radiation ranged from 0.5 to 60 E m2 daf1 and
was chiefly influenced by day length and cloud cover (Fig. 12).
Extinction
coefficients were calculated from light intensity measurements taken at high
tide at all three intensive study sites (Table 2).
These coefficients ranged
from 0.400 to 0.870 and were generally lower at the SAND and-FINE SAND sites
than at the SILT site.
An example of the effect of water depth on light available at the sediment surface is shown in Figure 13.
Measurements of light intensity at the
water surface, water depth, and the extinction coefficient were made in
Netarts Bay for a day in July and a day in September.
The light intensity
at the sediment surface was calculated for each hour between 8:00 a.m. and
4:00 p.m. PST, at three tidal elevations, by substituting the appropriate
light intensity, water depth and extinction coefficient into the expression:
= ie; where 1
is the light intensity at depth z, 10 is the light
intensity at the surface and Ti is the extinction coefficient.
A clear,
sunny day occurred in July; while in September, the sun only appeared between
11:00 a.m. and 12:30 p.m. PST.
Light intensity was not limiting for photo-
synthesis between 9:00 a.m. and 4:00 p.m. during the day in July; but in
September, the light intensity often fell below light-saturation of photosynthesis which was approximately 1
described in a later section).
E m2 h1 (see results of laboratory study
I
AM J
I
J
'II
111111
I
i
MONTH
A SO ND J FM
IJi
I
I
Temperature of air, sediment and water during the period from April, 1980, to March,
1981 in Netarts Bay. Bars Indicate daily
range of temperature at all intensive study
sites on the sampling dates.
10
I
III
I
I
iJX
LiJ
Figure 11.
I
Ui
II
I
II
H
z
Ui
a-
uJ
0
11111
jili
-
C)
I
l0
II
I
I
-
Figure 12.
----------------
0
0
0
D
J FM AM
S
PhotosynthetIcally active radiation (E nr2 day-i) for the period from May, 1980, to
May, 1981 at Netarts Bay.
MONTH
J JASON
S
._____
S.
0
S
.
.
S
0/
N 10/
-56-
Table 2.
Extinction coefficients ()a measured at high tide at the SAND, FINE
SAND and SILT intensive study sites. Light intensity at the urfac
and 1.0 in depth is photosynthetically active radiation (E m
sec
).
High tide was between 11:00 and 13:00 PST.
Light Intensity
Site
Date
Surface
SAND
13 May
1375
737
0.624
ii June
1250
670
0.624
July
1350
804
0.518
1000
509
0.675
1500
804
0.624
570
281
0.707
10 June
2100
1206
0.555
10 July
1800
1206
0.400
820
496
0.503
1500
804
0.624
May
615
295
0.735
9
June
800
335
0.870
9
July
460
241
0.646
8
August
870
375
0.842
5
September
680
375
0.595
ii
10 August
7
FINE SAND
SILT
a)
12 May
9
August
6
September
11
n= in I
September
- in I; where I
intensity at 1.0
in
depth.
1.0 in Depth
= surface light intensity and I
= light
-57-
I
I
I
oO°\ \
4
N
I
3
HIGH
I
/
I
1
2
-
I..'
I \
OMID
/SEPTI
£LOW
I
I
/
,
a
L
9:00
11:00
_L
1:00
3:00
PS.T
Figure 13.
Effect of water depth on light available to sedimentassociated algae in Netarts Bay for a day in July and
a day in September at three intertidal heights: HIGH
(1.5 m above MLLW), MID (1.0 in above MLLW) and LOW (0.5
m above MLLW). High tide was at noon (2.0 in above flLW)
Values were calculated using measured water levels,
extinction coefficients, and light intensities at the
water surface. The line at 1.0 E m2 hr- approximates
light saturation of photosynthesis.
-58-
Light transmission through the sediment at all three of the intensive study
sites was determined by measuring light transmission through 1 mm thicknesses of
sediment in petri dishes (Haardt and Nielsen, 1980).
Reduction of photosynthet-
ically active radiation to 1.0% of surface light intensity was reached at 2.55
mm at the SAND site, 2.00 mm at the FINE SAND site, and 1.30 mm at the SILT
Site.
Salinity in the water column of Netarts Bay ranged from 28 to 34 0/00
during the study.
35
/oo.
Values for interstitial water usually varied between 25 and
However, interstitial water at 2.0 m above fLLW in all sediment types
reached values as low as 5
/oo during rain storms or periods of terrestrial
runoff from ground water seepage.
During July, August, and September nutrient concentrations (NO2-No3, NH4,
PO4, and SiO3) in the water from the respirometer chambers were measured before
and after in situ incubation (Table 3).
The only significant changes in concen-
trations during the incubation period occurred when Enteromorpha prolif era
(Setch.) S.&G. was present in the chambers.
For example, the concentration of
NO2-NO3 decreased from 3.23 to 1.05 I.M during the six-hour incubation period in
August at the SAND site.
2.
Organic Matter
There was a significant positive correlation (n = 34, r = 0.82; p < .01)
between sediment mean grain size in phi-units () and the organic matter concentration (AFDW) in the top cm of sediment.
The corresponding regression
equation expressing mean grain size as a predictor of organic matter was AFDW =
-89.54 + 109.21
1?.
An analysis of variance indicated that there were signif-
icant differences (P < .01) in organic matter concentration in the top cm of
sediment associated with differences in sediment type (Appendix I).
The SILT
site had the highest mean organic matter concentration followed by the FINE SAND
site and the SAND site, respectively (Table 4).
There also were significant
differences (P < .01) in the concentration of organic matter associated with the
effects of tidal height, time, and a two-way interaction between sediment type
and tidal height (Table 4, Figs. 14 and 15).
highest during the summer.
Organic matter concentration was
At the SILT and FINE SAND sites, the transects at
2.0 m above MLLW had the highest concentrations of organic matter; while at the
SAND site, the highest concentrations were at 0.5 m above MLLW.
The ratio of organic matter in the top cm of sediment to that at the 4 to
5 cm depth was calculated and used as an index of mixing of organic matter in
the sediment.
No significant differences related to the effects of sediment
type, tidal height, or time were found in the bay sediments relative to this
ratio.
The mean value of the ratio for all sediment types was 1.50 indicating
that organic matter usually was present at both depths in similar concentrations.
-59-
Table 3.
Initial nutrient concentrations (iiM) in respirometer chambers at
the SAND, FINE SAND and SILT intensive study sites during sampling
in July, August and September.
July
August
September
NO2-NO3
SAND
3.23
3.23
0.81
FINE SAND
0.16
0.32
0.16
SILT
0.48
0.24
0.16
SAND
0.56
1.11
2.78
FINE SAND
0.56
2.22
2.22
SILT
1.11
1.67
2.22
0.48
0.48
0.34
0.39
0.39
0.39
0.39
0.39
0.39
14.46
14.46
10.51
11.83
11.17
17.09
13.14
12.49
15.77
NB4
Table 4.
Concentration of organic matter (g m2) in the top cm of sediment,
expressed as ash-free dry weight, in Netarts Bay at the SAND, FINE
SAND and SILT sites.
1.0 m (2), 1.5
in
Intertidal levels are above MLLW:
(3), and 2.0 (4).
Values are site and tidal level
means () and standard errors (SE) of n observations.
Site
SE
SAND
Level
1
43
10
2
11
3
11
11
4
FINE SAND
Level
38
1
2
10
3
11
4
11
1
43
10
2
11
3
11
11
SILT
Level
6
4
0.5 in (1),
134.05
196.95
138.88
119.73
86.36
8.56
15.71
14.72
203.88
182.11
201.53
205.38
216.38
33.07
23.20
20.30
16.82
17.02
377.76
385.99
350.07
325.61
450.11
13.93
19.09
20.18
19.42
33.59
9.93
7.41
-61-
lOM t MLLW datum
ScC.
SANO
T±SE
500.
£FINE SAND
o SILT
40 0
E
4
a'
301
0
U-
201
-
r MA M
J
SO N
A
J
J FM
0
MONTH
O.5M i MLLW datum
_1
SAND
iFINE SAND
± SE
o SI LI
E
a'
300
0
U200
too
r
ri
U
M
J
A
S
0
N
0
J
F
M
MONTH
Figure 14.
Concentration of organic matter in the top cm of sediment
expressed as ash-free dry weight (AFDW) at intensive study
sites from March, 1980, to March, 1981.
Sites are SAND,
FINE SAND, and SILT at 1.0 m and 0.5 in above MLLW.
Values
are means of three replicates.
-62-
2.OM + MLLW datum
S SAND
600
7
SE
£ FINE SAND
0 SiLT
500
a
N
TI/f
400
/t1
E
0
Li.
/
FM AM
A SO ND J FM
J
.J
MONTH
I.5M + MLLW datum
±SE
500
SAND
£ FINE SAND
o SI LI
a
N
E
300
0
U.
F
MA M
J
J
A
SON D
J
FM
MONTH
Figure 15.
Concentration of organic matter in the top cm of sediment
expressed as ash-free dry weight (AFDW) at intensive study
sites from March, 1980, to March, 1981. Sites are SAND,
FINE SAND, and SILT at 20 m and 1.5 m above MLLW. Values
are means of three replicates.
-63-
Sediment-associated total organic matter was separated into its component
fractions (Table 5).
The total represents monthly measurements of organic
matter concentration in the top cm of sediment.
Microalgal biomass was calcu-
lated using a conversion factor between chlorophyll a and organic matter
determined in the laboratory throughout the year with epipelic diatoms isolated from the sediment (see page 109 of this report).
For these calcula-
tions, microalgal organic matter concentration = 166.98 x chlorophyll a concentration.
Animal organic matter was determined by harvesting in April.
The
concentration of detritus was calculated by the subtraction of microalgal and
animal organic matter from the total.
The results of these calculations indi-
cated that detritus was the major component of organic matter in these sediments.
3.
Chlorophyll a Concentration
An analysis of variance indicated that there were significant differences
(P < .01) in the chlorophyll a in the top cm of sediment associated with the
effects of sediment type, tidal height, time, and a two-way interaction
between sediment type and tidal height (Appendix I, Figs 16 and 17).
The SILT
site had the highest mean chlorophyll a concentration, followed by the FINE
SAND site and the SAND site, respectively (Table 6).
Chlorophyll a concentra-
tion was highest during the spring at the SAND and FINE SAND sites; while
during the fall and winter, the concentration was highest at the SILT site.
At the SILT and FINE SAND sites, the 2.0 m transects had the highest concentrations of chlorophyll a; while at the SAND site, the highest concentrations
were found for the transect at 1.0 m above MLLW.
-64-
Table 5.
Ranges of component fractions of organic matter (g m2) in the top
cm of sediment, expressed as ash-free dry weight at the intensive
study sites.
Total organic matter and animal organic matter were
measured by direct sampling.
Microalgal organic matter was calcu-
lated from chlorophyll a concentrationsa.
Detrital organic matter
was calculated by the subtraction of microalgal and animal organic
matter from the total organic matter.
Fraction
Total
SAND
Intensive Study Site
FINE SAND
SILT
69.8-268.4
128.0-303.2
256.5-575.0
Microalgae
1.6-23.2
4.3-31.8
4.3-48.0
Animals
1.3-11.8
3.9-8.2
1.1-5.5
Detritus
(66.9-233.4)
(119.8-263.2)
(251.1-521.5)
a)
Microalgal organic matter concentration = chlorophyll a concentration
x 166.98 (see pages
of this report).
-65-
MLLW datum
SANO
!±SE
£FINE SAND
o St LI
N
at
-J
F MA M
A
J
[1
M
MONTH
0.5 M f MLLW datum
SAND
±SE
LEINE SAND
0 Si LI
'S
at
-J
MA M
J
A
M
MONTH
Figure 16.
Concentration of chlorophyll a in the top cm of sediment
(CHL a) at intensive study sites from March, 1980, to
March, 1981. Sites are SAND, FINE SAND, and SILT at
1.0 m and 0.5 above MLLW. Values are means of six replicates.
-66-
2.OM + MLLW datum
SAND
I
£FINE SAND
tSE
OS I LT
1
a
N
zoo
-J
z
U
L
F'
J
I
M AM .J
J
SON D J FM
I
A
I
I
MONTH
I
I
I
I
F
j
I
I
I
F
I.5M I- MLLW datum
.SAND
TtSE
£ FINE SAND
051 LI
a
200
N
E
-J
iIOO
U
F
MA
M
J
1J
A
SON
D
J
FM
MONTH
Figure 17.
Concentration of chlorophyll a in the top cm of sediment
(CHL a) at intensive study sites from March, 1980, to March,
Sites are SAND, FINE SAND, and SILT at 2.0 m and 1.5
1981.
m above MLLW. Values are means of six replicates.
-67-
Table 6.
Concentration of chlorophyll a (mg mg2) in the top cm of sediment
in Netarts Bay at the SAND, FINE SAND and SILT sites.
Intertidal
levels are above MLLW: 0.5 m (1), 1.0 m (2), 1.5 m (3), and 2.0 m
(4).
Values are site and tidal level means (i) and standard
errors (SE) of n observations.
Site
SE
SAND
45
Level
1
2
FINE SAND
Level
3
12
4
11
42
1
6
2
12
3
12
12
4
SILT
Level
10
12
1
2
3
4
46
10
12
12
12
46.18
79.71
66.09
25.12
16.94
6.02
11.59
13.24
4.83
2.81
74.72
83.12
54.73
73.90
91.34
7.37
20.16
13.26
12.41
3.89
93.70
49.50
69.16
82.86
11.07
8.87
20.89
9.61
24.45
165.91
The ratio of chlorophyll a concentration in the top ciii of sediment to
that at the 4 to 5 cm depth was calculated as an index of mixing of chlorophyll a in the sediment.
High chlorophyll a ratios resulted from a paucity of
chlorophyll a in the 4 to 5 cm depth sediment, while relatively low values
indicated that chlorophyll a was mixed to the 4 to 5 cm depth.
There were
significant differences (P < .01) in the chlorophyll a ratios associated with
the effects of sediment type, tidal height, and a two-way interaction between
sediment type and time (Appendix I).
The SAND site had the highest mean
chlorophyll a ratio followed by the SILT and the FINE SAND sites (Table 7).
At all sites, the mean ratio was higher at the transects 2.0 m above MLLW than
at the other intertidal tansects.
4.
Primary Production
An analysis of variance indicated that there were significant differences
(P < .05) in gross primary production of microalgae associated with the effect
of time (Appendix I).
Maximum gross primary production occurred in the summer
when Enteromorpha sporelings were abundant in the sediment community (Figs. 18
and 19).
When production by Enteromorpha sporelings was included in the calculations, the FINE SAND site had the highest mean rate of gross primary production followed by the SAND site and the SILT site (Table 8).
If samples with
Enteromorpha sporelings were excluded, all sediment types had similar mean
rates of gross primary production.
Because of the difference in growth form, the contribution of Enteromorpha prolifera to total primary production at the intensive study sites was
estimated by experiments with isolated plants in the laboratory (see details
Table 7.
Ratio of the chlorophyll a concentration in the top cm of sediment
to the concentration at the 4 to 5 cm depth in Netarts Bay at
the SAND, FINE SAND and SILT sites.
MLLW:
Intertidal levels are above
0.5 m (1), 1.0 m (2), 1.5 m (3), and 2.0 (4).
Values are
site and tidal level means () and standard errors (SE) of n
observations.
Site
SE
SAND
Level
1
43
10
2
11
3
11
11
4
FINE SAND
Level
38
1
6
2
10
3
11
4
11
SILT
43
Level
41.73
2.25
2.40
56.13
102.53
13.49
0.38
0.49
39.80
26.94
9.31
1.21
3.25
1.27
27.27
13.86
0.21
11.50
1.53
3.29
17.35
0.22
4.19
0.24
69.74
1
10
2
11
3
4
11
1.51
11
38.77
1.81
0.22
50.23
-70I
I
I
I
I
I
I
I
I
I
I
I
I
I.OM + MLLW datum
SAND
£ FINE SAND
200-
oSILT
E
C-,
QQI
0
a-
w
FM AM J
J
A
MONTH
I
1
I
I
I
I
I
I
I
I
I
I
O.5M +MLLW datum
. SAND
tSE
200-
£ FINE SAND
-
oSILT
E
0
a-
100-
-
a-
L
1
F
M
I
A
t
M
J
J
i
i
L
A SO ND J
I
I
MONTH
Figure 18.
Gross primary production (GPP) at intensive study sites from
Nay, 1980, to March, 1981.
Sites are SAND, FINE SAND, and
SILT at 1.0 m and 0.5 m above MLLW. Values are means of two
replicates from May to September and three replicates from
October to March.
2
fl's
It)
]NIJ
4
ONVS
-J
40
iio
w
U,
+1
iRON Os
U)
=
z
0
C
T/
\\
V
d
o
o
0
0
c'J
(1
Figure 19.
D
5w) ddD
Gross primary production (GPP) at intensive study sites from
May, 1980, to March, 1981.
Sites are SAND, FINE SAND, and
SILI at 1.5 m above MLLW. Values are means of two replicates
from May to September and three replicates from October to
March.
-72-
Table 8.
Intertidal gross primary production (mg C m2 hr') in Netarts Bay
at the SAND, FINE SAND and SILT sites.
MLLW:
Intertidal levels are above
0.5 m (1), 1.0 m (2), 1.5 m (3), and 2.0 (4).
Values are
site and tidal level means () and standard errors (SE) of n
observations assuming a photosynthetic quotient of 1.2.
Site
SE
Including Enteromorpha
sporelirigs:
SAND
25
Level 1
7
2
8
3
8
4
2
FINE SAND
Level 1
22
2
8
3
8
4
2
SILT
4
37.43
35.80
62.16
23.04
8.98
7.94
7.26
21.28
3.38
2.34
47.15
84.88
40.78
47.13
27.10
13.84
65.75
15.53
19.11
14.56
3.97
5.75
4.46
4.25
22.12
2
8
3
8
4
3
25.06
20.07
19.34
21.42
53.70
SAND
23
27.82
3.25
FINE SAND
20
28.05
5.12
SILT
26
25.06
3.97
26
Level 1
7
Excluding Enteromorpha
sporelings:
-73-
in a later section).
This alga was conspicuous from June to August at the
SAND and FINE SAND sites, and the maximum biomasses at these sites were 149
and 162 g C m2, respectively (Table 9).
the SILT site.
Enteromorpha was never present at
The estimated contribution of Enteromorpha to the annual net
primary production at the SAND and FINE SAND sites was 2,712 and 2,886 g
Cm2yr', respectively, an enormous elaboration of organic matter.
While
growth of Enteromorpha appeared to be related to seasonal increases in
temperature and day length, it is not possible to rule Out nutrient dynamics
associated with the upwelling phenomenon as a possible cause of the high
production of this alga during the summer months.
Its absence at the SILT
site was probably related to the relatively high turbidity and instability of
the sediments at this location.
There were significant differences (P K .01) in community oxygen uptake
associated with the effect of sediment type (Appendix I).
The FINE SAND site
had the highest mean rate of community oxygen uptake followed by the SILT
site and the SAND site (Table 10).
There were also significant differences
(P < .05) in community oxygen uptake associated with the effects of time and a
two-way interaction between sediment type and tidal height (Fig. 20).
Maximum
community oxygen uptake in all sediment types was detected in the summer when
temperature was relatively high.
The ratio of daily gross primary production to daily community oxygen
uptake was calculated using data from the primary production estimates of
this study.
Daylength at the sediment surface ranged from 6 h in December to
12.2 h in June.
This ratio is an index of benthic autotrophy relative to
heterotrophic activity in the sediment community, the higher values indicating
-74-
Table 9.
Maximum biomass (BIOMASS) of Enteromorpha prolifera, and the annual
contribution of Enteromorpha prolifera to the rates of gross
primary production (GPP), respiration (RESP) and net primary
production NPP), at the SAND and FINE SAND sites in Netarts Bay.
BIOMASS (g C
m2)
GPP (g c m2 yr1)
RESP (g C m2
yr)
NPP (g C m2 yr')
SAND
FINE SAND
149
162
3691
3880
907
994
2712
2886
-75-
Carbon equivalent of the intertidal community oxygen uptake
Table 10.
(mg c m2 hr') in Netarts Bay at the SAND, FINE SAND and SILT
sites.
Intertidal levels are above MLLW:
1.5 m (3), and 2.0 (4).
0.5 m (1), 1.0 m (2),
Values are site and tidal level means ()
and standard errors (SE) of n observations assuming a respiratory
quotient of 1.0.
Site
SE
SAND
25
Level
FINE SAND
Level
1
7
2
8
3
8
4
2
22
1
4
2
8
3
8
4
2
SILT
26
Level
1
7
2
8
3
8
4
3
11.49
13.81
17.72
6.57
1.20
1.86
2.31
3.57
2.33
1.20
27.16
21.18
28.98
29.05
24.63
3.87
6.50
6.49
8.12
5.76
18.34
22.74
17.23
20.67
7.93
2.37
5.56
3.48
4.22
2.33
-76-
I.5M+ MLLW
£
SAND
£
50
/o \/
£ FINE SAND
0 SILT
I.OM+MLLW
0
A_A
!°\
)5O
0
0
0.5M +MLLW
0
50
------
0
M
J
A
S
U
N
- _ - a
0
J
F
M
MONTH
Figure 20.
Community oxygen uptake (OUPTK) at intensive study sites from
May, 1980 to March, 1981. Sites are SAND, FINE SAND, and SILT
at 1.5 in, 1.0 in and 0.5 in above MLLW. Values are single observations from May, 1980, to September, 1980, and means of three
replicates from October, 1980, to March, 1981.
-77-
relatively greater gross primary production.
The SAND site had the highest
mean ratio followed by the FINE SAND site and the SILT site (Table 11).
There
were no significant differences in the mean values of this ratio associated
with effects of either tidal height or time.
The ratio of gross primary production to chlorophyll a concentration in
the top cm of sediment was calculated to give a measure of production per unit
of microalgal chlorophyll a (Table 12).
The mean value for this ratio ranged
from 0.51 (SILT site) to 1.21 (FINE SAND site).
There were no significant
differences among the mean values for this ratio associated with the effects
of sediment type, tidal height, or time (Appendix I).
5.
Relationships Among Variables
Table 13 gives Pearson product-moment coefficients of correlation (r) for
selected pairs of physical and biological variables monitored in Netarts Bay
during the study.
While such correlations are often unrelated to causation,
they do provide a useful initial insight into the structure of the data.
At
the 5% significance level, 13 r values were judged to be significantly different from zero.
However, relationships suggested by values below 0.50 are
undoubtedly weak or spurious, so such tests are essentially useless for our
purpose.
Here, we adopt the view that the coefficients are simply an indi-
cation of the degree to which variables covary and indicate some of the higher
values that are relevant for data interpretation.
In general, correlations among the variables in Table 13 were low; and
only 4 out of 28 values were greater than 0.50.
Among physical variables,
daylength and temperature had the highest r value (0.74).
Mean sediment size
in phi units was the only physical variable that had a correlation greater
than 0.50 with a biological variable; its correlation with organic matter
concentration in the top cm of sediment was 0.82.
Among biological variables,
-78-
Table 11.
Ratio of daily gross primary production to daily community oxygen
uptake in Netarts Bay at the SAND, FINE SAND and SILT sites.
Intertidal levels are above MLLW:
0.5 m (1), 1.0 m (2), 1.5 m (3),
Values are site and tidal level means (T) and
and 2.0 (4).
standard errors (SE) of n observations.
Site
SE
SAND
25
Level
FINE SAND
Level
1
7
2
8
3
8
4
2
22
1
4
2
8
3
8
4
2
SILT
26
Level
1
7
2
8
3
8
4
3
3.19
1.13
1.56
7.24
0.71
1.69
0.17
0.40
5,19
0.33
0.77
1.42
0.65
0.69
0.27
0.20
0.86
0.26
0.75
0.44
0.48
0.51
2.86
0.21
0.21
0.21
0.14
0.07
0.09
1.47
-79-
Ratio of gross primary production to chlorophyll a concentration
(mg C hr1 mg) in Netarts Bay at the SAND, FINE SAND and SILT
sites.
Intertidal levels are above MLLW:
0.5 m (1), 1.0 m (2),
1.5 m (3), and 2.0 (4). Values are site and tidal level means ()
and standard errors (SE) of n observations.
Table 12.
Site
SE
SAND
25
Level
FINE SAND
Level
1
7
2
8
3
8
4
2
22
1
4
2
8
3
8
4
2
SILT
26
Level
1
7
2
8
3
8
4
3
0.95
0.55
1.16
1.17
0.67
0.15
0.10
0.41
0.17
0.36
1.21
2.13
1.13
1.30
0.41
0.45
1.62
0.62
0.83
0.23
0.51
0.57
0.54
0.54
0.31
0.08
0.12
0.15
0.16
0.08
-
0.63*
0.12
0.82*
0.74*
-
0.45*
0.07
0.15
-0.01
_0.26*
0.15
-0.07
TEMP
0.11
0.38*
_0.24*
0.42*
-
0.01
-0.10
_0.31*
-0.07
DAYL
0.29*
SEDMEAN
0.08
0.13
0.08
OUPTK
The * symbol indicates that the value is significantly different from zero at the 57. level.
TEMP
DAYL
SE DME AN
OUPTK
GPP
-
0.46*
0.81*
-0.05
GPP
CHLR
CHLR
0.40*
AFDW
0.18
-
CHLS
A matrix of Pearson product-moment coefficients of correlation (r) for selected
pairs of physical and biological variables monitored in Netarts Bay from March
1980 to March 1981. The variables are chlorophyll a concentration in the top
cm of sedinent (CHLS), organic matter concentration in the top cm of sediment
(AFDW), chlorophyll a concentration in the top cm of sediment in the respirometer
cores (CHLR), of gross primary production (GPP), community oxygen uptake (OUPTK),
sediment mean grain size (SEDMEAN), daylength (DAYL), and water temperature (TEMP).
AFDW
CHLS
Table 13.
there was a relatively high correlation between chlorophyll a concentration in
the top cm of sediment and that in the top cm of cores used in the respiro-
meter (0.81) and between gross primary production and chlorophyll a concentration in the respirometer cores (0.63).
Because of the time and problems associated with the direct measurement
of gross primary production (GPP) in the field, it was of interest to examine
other variables as potential predictors of GPP.
From the correlation
analysis, the only likely predictor was the chlorophyll a concentration in the
top cm of sediment (CHLR).
The linear and curvilinear equations corresponding
to each intensive study site and to the pooled data for all sites are presented in Table 14.
These equations represent the prediction of GPP for
microalgal assemblages in the absence of Enteromorpha sporelings.
For this
relationship, the highest R2 value was found for the SILT site (0.55), but all
values were relatively low.
However, the relationship derived from the pooled
data from Netarts Bay resembles the linear equation obtained for data from
five intensive study sites on the Columbia River estuary, although regression
analyses indicated that the curve fit was more satisfactory for the Columbia
River data (Table 14).
Since the y-intercept was relatively high for the
Netarts Bay data (9.57 mg C hr1), it was desirable to examine several other
models.
From a biological perspective, it makes sense to force the line
through the origin and investigate a linear and curvilinear relationship.
Table 14, such models are presented for both the Netarts Bay and Columbia
River data; and residual mean squares are provided as a basis for within
estuary comparisons.
Based on data from this study, the most satisfactory
In
-82-
Table 14.
Linear and curvilinear equations expressing gross primary production (GPP) as a
function of the concentration of chlorophyll a (CHLR)
Units for GPP and CHLR are mg hr
in the top cm of sediment.
and mg, respectively.
The models correspond to
the SAND, FINE SAND and SILT sites at Netarts Bay, and to the pooled data for
Netar-t-s Bay and the Columbia River Estuary.
Residual Mean
Location
R2
Square
Netarts Bay
SAND
GPP = 10.47 + 0.41 CHLR
23
0.50
FINE SAND
GPP = -3.56 + 0.65 CHLR
20
0.37
SILT
GPP =
7.60 + 0.30 CHLR
26
0.55
1.
GPP =
9.57 + 0.35 CHLR
69
0.40
220.7
2.
GPP =
8.22 + 0.40 CHLR - 0.00025 (CHLR)2
69
0.40
223.6
3.
GPP =
0.48 CHLR
69
-
246.6
4.
GPP =
0.61 CHLR - 0.0012 (CHLR)2
69
-
228.9
1.
GPP =
2.90 + 0.30 CHIR
56
0.73
474.0
2.
GPP = -2.80 + 0.38 CHLR - 0.00017 (CHLR)2
56
0.74
464.2
3.
GPP =
0.31
56
-
468.8
4.
GPP =
0.36 CHLR - 0.00014 (CHLR)2
56
-
457.5
Pooled Data:
Columbia River
Pooled Data:
HLR
model for predicting GPP in Netarts Bay is model 4, i.e., the quadratic function forced through the origin:
GPP = 0.61 CHLR
-
0.0012 (CHLR)2
In the case of the Columbia River estuary, either the linear are quadratic
functions are probably satisfactory.
In summary, chlorophyll a concentration
in the top cm of sediment is a relatively good predictor of GPP in the Columbia
River estuary, a system under the influence of high freshwater discharge; while
in Netarts Bay, a more marine system, such predictions are less reliable.
The
disruptive influence of burrowing marine animals is one obvious explanation for
the difficulty in predicting GPP at certain locations in Netarts Bay.
Mean sediment grain size was a relatively good predictor of the organic
matter concentration in the top cm of sediment.
This relationship was improved
slightly by adding the chlorophyll a concentration in the top cm of sediment to
the model.
The linear equations are
AFDW = -89.54
109.21 SEDMEAN
and
AFDW = -123.50
104.41 SEDMEAN + 0.92 CHLR,
where AFOW is the organic matter concentration (g m2), SEDNEAN is the grain
size in phi units, and CHLR is the chlorophyll a concentration (mg m2);
corresponding R2 values are 0.67 and 0.73.
Interpretation of Autotrophic Patterns
Sediment characteristics of Netarts Bay remained relatively constant at
the intensive study sites during the study period.
This would be expected for
a bay which does not receive large seasonal inputs of terrestrial runoff and
-84-
associated silt.
Sediment type ranged from medium sand to coarse silt and
corresponded to sources of material for the bay.
Changes in sediment height in
Netarts Bay during the spring and summer corresponded to areas with conspicuous
wave activity and strong water currents.
western side of the bay.
Most of these areas were on the
Frostick and McCave (1979) found an association
between algal growth and sediment accretion, with subsequent erosion of sediment when the algae died.
erosion.
Wave action also strongly influenced the amount of
No simple association between algal growth and sediment accretion was
found in Netarts Bay, although it was observed that Enteromorpha did trap large
amounts of sediment.
Mucus secreted by diatoms, blue-green algae, and
flagellates also helps to bind sediment (Coles, 1979; Frostick and McCave,
1979).
Organic matter concentration in the top cm of sediment was related to mean
grain size, with the highest mean concentration found at the SILT site and the
lowest at the SMD site.
Seasonal changes in organic matter corresponded to
changes in plant, animal, and detrital biomass.
Similar seasonal changes were
observed in other estuaries (e.g., Edwards, 1978; Cadée and Hegeman, 1977).
In
Netarts Bay, there were no large differences between organic matter concentration in the top cm of sediment and that at the 4 to 5 cm depth.
However,
differences in the chemical composition of organic matter may vary with depth
as sediment is disturbed by benthic animals (Johnson, 1977).
In Netarts Bay, large amounts of Enteromorpha and Zostera were transported
to the strand line at 1.0 m above MLLW during the summer and the fall.
This
accumulation occurred primarily on the shores furthest away from the mouth of
the bay.
The material was fragmented and incorporated as organic matter into
the intertidal sediments rapidly during these seasons.
Josselyn and Mathison
(1980) also observed large biomasses of macrophyte litter at the strand line in
Great Bay, New Hampshire, reporting that seaweeds composed 35 to 85% of the
material thoughout the year.
In general, chlorophyll a concentration in the top cm of sediment was
higher at the SILT site than at the SAND site.
A similar pattern was found for
other estuaries (Cad&e and Hegeman, 1977; Coles, 1979; Colijn and Dijkema,
In Netarts Bay, there was a relatively high concentration of chloro-
1981).
phyll a in the top cm of sediment at 2.0 m above MLLW, a pattern apparently
related to abundant soil moisture and the lack of benthic animals.
algae also were common at this location.
Blue-green
At lower tidal heights at the SILT
site (< 1.5 m above NLLW), the chlorophyll a concentration in the top cm of
sediment was the same or lower than that at the FINE SAND and SAND sites.
At
these tidal heights, the flora was dominated by epipelic and epipsammic diaChlorophyll a concentration in the top cm of sediment at the FINE SAND
toms.
site at 2.0 in above MLLW was maximum during the summer, a maximum that was
probably related to high moisture, abundant blue-green algae, and the lack of
benthic animals.
The SAND site had low chlorophyll a concentrations, a pattern
associated with a wave-exposed beach which lacked moisture during exposure to
the air.
Animal holes in the sediment, made primarily by Callianassa, were abundant
at all study sites at the tidal height of 1.5 m above MLLW.
These perforations
resulted in a decrease in chlorophyll a concentration in the top cm of sediment
expressed on an areal basis.
Animal holes were more abundant at the SILT site
than at the FINE SAND and SAND sites at tidal heights less than 1.5 m above
MLLW.
sites.
However, at these tidal heights, benthic animals were abundant at all
Other factors limiting microalgal biomass at the study sites were scouring
and turbidity associated with water movements and interactions with
Enteromorpha and Zostera.
At times, both Enteromorpha and Zostera shaded
sediment-associated microalgal populations and also competed with microalgac
for space.
Large "ropes" of Enteromorpha became entangled in Zostera beds and
trapped large amounts of sediment, an event which inhibited the growth of
microalgae.
Similar factors apparently limited the production of microalgae
during long-term studies in salt marshes (Gallagher and Daiber, 1974; Van
Raalte, et al., 1976).
The ratio of the chlorophyll a concentration in the top cm of sediment to
the concentration at the 4 to 5 cm depth was highest at 2.0 m above MLLW at all
three intensive study sites.
The 2.0 m transect at the SAND site was a
relatively barren beach strand line, while the 2.0 m transects at the FINE SAND
and SILT sites had compacted subsurface sediments.
At these sites, high ratios
apparently were associated with the relative stability of these sediments and
the poor survival of subsurface populations of microalgae once they have been
buried in compacted subsurface sediment.
At transects lower than 2.0 m above
MLLW, animal activity and scouring disturbed the sediment and lowered the
chlorophyll a ratio.
The complicated temporal pattern of chlorophyll a distribution apparently
was controlled by sediment moisture, animal activity, macrophyte cover, water
currents, and wave action.
Maximum chlorophyll a concentrations were observed
in the spring during a period of relatively high microalgal growth and inactivity of benthic animals and again in the fall during fair weather and a decrease
in animal activity.
Experiments in the field and in the laboratory have indi-
cated that benthic animals inhib±ted xnicroalgal biomass accumulation signifi-
-87-
candy (see later section of this report; Admiraal, 1977d; Coles, 1979).
In
other estuaries, chlorophyll a concentration near the sediment surface also was
related negatively to wave action, water currents, and storm activity
(Pamatmat, 1968; Gallagher and Daiber, 1974; Colijn and Dikjema, 1981).
Maximum gross primary production occurred during the summer at all three
intensive study sites.
Although large plants of Enteromorpha were excluded
from production measurements, sporelings were present in the sediment at the
SAND and FINE SAND sites and presumably contributed significantly to sedimentassociated gross primary production in the summer.
When Enteromorpha was
excluded, the mean hourly rates of gross primary production were similar for
all intensive study sites.
This is in contrast to the mean chlorophyll a
concentration in the top cm of sediment which was highest at the SILT site.
The growth of blue-green algae at 2.0 m above MLLW contributed large biomasses
at this site but apparently did not increase the hourly rate of gross primary
production.
Other studies have detected a diurnal rhythm of sediment-associated algal
primary production (Pamatmat, 1968; Gallagher and Daiber, 1974).
such rhythms were found during the daylight hours in Netarts Bay.
However, no
Other
factors which were not measured in Netarts Bay, but could possibly explain
variation in primary production, include microalgal migration in the sediment,
sediment stability, grazing pressure, and import-export of microalgal biomass
(Cadêe and Hegeman, 1974; Pamatmat, 1968).
Light intensity at the intertidal sites was usually 10 to 20% of full
sunlight, an intensity that was above the level necessary for light saturation
of photosynthesis (Admiraal, 1977a; Colijn and van Buurt, 1975).
Exceptions to
this included days of heavy cloud cover and fog and periods of wind-induced
wave activity which stirred up the sediments in certain areas.
Apparently
photosynthesis was controlled by daylength, which was determined by cloud
cover, turbidity, water depth, and sunrise-sunset times.
The control of
photosynthesis in sediment-associated microalgae by daylength also has been
observed in other estuaries (Cad&e and Hegeman, 1974; Admiraal and Peletier,
1980; Pamatmat, 1968).
Maximum community oxygen uptake occurred during summer, corresponding to
increases in temperature, organic matter concentration and metabolic activity.
A similar pattern was found by Pamatmat (1968) and Duff and Teal (1965).
The
FINE SAND site apparently had the most favorable conditions for the growth of
animals and plants.
Apparently community oxygen uptake was not limited by
substrate concentration, as the mean organic matter concentration was highest
at the SILT site while the mean oxygen uptake was maximum at the FINE SAND
site.
Some earlier work indicated that community oxygen uptake may be corre-
lated with organic matter concentration (Pamatmat, 1975; Edwards, 1978).
Much
of the organic matter at the SILT site was refractory (e.g., twigs and leaves)
and derived from terrestrial sources.
This material was probably relatively
unavailable to the detrital food web.
Further research is necessary to parti-
tion the various organic components in estuaries into available and unavailable
fractions (Johnson, 1977).
The highest ratios of daily gross primary production to daily community
oxygen uptake occurred at the SAND site when sporelings and young plants of
Enteromorpha were dominant.
The communities at the SILT and the FINE SAND
sites had ratios below unity and were, therefore, supported in part by detrital
inputs.
The ratio of gross primary production to chlorophyll a concentration in
the top cm of sediment was relatively constant throughout the year at all three
intensive study sites.
Chiorophyllides which are included in the measurement
of chlorophyll a represent a possible source of variation in the estimated
ratio of gross primary production to chlorophyll a concentration, as chlorophyllides are not photosynthetically active pigments (Whitney and Darley,
1979).
Moreover, chlorophyll a sampled from the top cm of sediment included
microalgal biomass, which was below the level of 1% of the surface light
intenstiy (1.3 to 2.6 mm depth) an intensity at which photosynthesis is equal
to or below respiratory losses.
Also, diurnal rhythms of microalgal migration
and photosynthetic activity control the proportion of biomass able to photosynthesize in the surface sediments (Pamatmat, 1968; Taylor, 1964); and
seasonal variations in the ratio of carbon to chlorophyll a may account for
fluctuations in the ratio of gross primary production to chlorophyll a (Jonge,
1980).
Jonge (1980) found a negative correlation between microalgal growth
rate and the ratio of carbon to chlorophyll a in estuarine sediment for a
period of one year.
A summary of the seasonal and annual production dynamics of microalgal
assemblages for the three intensive study sites is presented in Tables 15-17.
Mean microalgal biomass, gross primary production, and community oxygen uptake
were calculated from data reported in Figures 16, 17, 18, 19, and 20, assuming
a carbon to chlorophyll a ratio of 83.49.
Estimates of microalgal respiration,
net primary production, and non-algal oxygen uptake are based on the assumption
that the hourly rate of algal respiration is 29% of the hourly rate of gross
primary production.
These assumptions are derived from experimental work
1
Table 15.
Estimates of seasonal sediment-associated mean microalgal biomass
and microalgal production in Netarts Bay at the SAND site. The
The variables,
tidal levels are 0.5 m, 1.0 m and 1.5 in above MLLW.
expressed as g Cm2, include: mean seasonal and annual biomass of
microalgae (BIOMASS), and the seasonal (90 days) and annual (360
days) gross primary production (GPP), microalgal respiration (RESP),
net primary production (NPP), community oxygen uptake (OUPTK) and
non-algal community oxygen uptake (NON-ALGAL OtJPTK). Seasonal rates
were calculated by multiplying hourly rates by daylenth and adding
The hourly rate of
daily rates for the appropriate period.
iuicroalgal respiration was assumed to be 29% of the mean hourly rate
of gross primary production, a value determined by laboratory
experiments (see page
in this report). NON-ALGAL OUPTK equals
OUPTK - RESP.
NON-ALGAL
Season
BIOMASS
GPP
RESP
NPP
OIJPTK
OUPTK
Winter
0.5 in
1.0 in
1.5 in
Spring
0.5 m
1.0 m
1.5 in
Summer
0.5 in
1.0 m
1.5 in
4.61
5.00
1.44
9.54
18.00
18.60
8.97
17.17
17.83
0.57
0.83
0.77
13.44
9.78
4.54
4.47
**
**
7.32
4.16
2.30
30.45
32.76
16.97
21.30
23.30
11.91
9.15
9.46
5.06
32.61
45.47
14.79
11.31
22.17
2.88
6.50
10.20
2.17
56.67
125.18
21.59
34.01
75.57
13.03
22.66
49.61
8.56
39.24
60.04
23.46
5.23
**
10.43
6.44
5.99
1.85
10.88
28.53
17.70
8.84
23.81
16.38
2.04
4.72
1.32
24.35
24.74
7.23
15.51
0.93
**
6.22
6.34
1.94
107.54
204.47
74.86
73.12
139.85
59.15
34.42
64.62
15.71
109.64
140.03
50.02
36.52
23.10
13.31
Fall
0.5 in
1.0 in
1.5 in
Annual
0.5 in
1.0 in
1.5 in
**Indication of a negative value for NON-ALGAL OUPTK; negative values are
assumed to be zero for the estimation of annual NON-ALGAL OUPTK.
-91-
Table 16.
Estimates of seasonal sediment-associated mean microalgal biomass
and microalgal production in Netarts Bay at the FINE SAND site.
Variables
The tidal levels are 0.5 m, 1.0 m and 1.5 m above MLLW.
and method of calculation are the same as described for Table 15.
BIOMASS
GPP
RESP
NPP
OUPTK
NON-ALGAL
OUPTK
2.59
5.62
9.50
15.83
11.88
9.00
14.77
11.01
0.50
1.06
0.87
13.00
26.09
26.16
4.00
11.32
15.15
7.07
5.70
5.69
21.92
28.85
29.21
14.06
17.73
18.77
7.86
11.12
10.44
45.62
54.33
58.22
31.56
36.60
39.45
3.35
4.88
4.95
101.92
75.11
114.72
64.50
44.66
67.52
37.42
30.45
47.20
36.57
83.37
124.78
38.71
57.26
4.05
4.08
18.00
25.91
6.83
12.00
20.09
5.51
6.00
5.82
1.32
21.00
84.35
15.89
9.00
64.26
10.38
5.21
4.31
5.09
151.34
145.70
162.64
99.56
97.25
102.81
51.78
48.45
59.83
116.19
248.14
225.05
44.56
150.89
122.24
-
**
**Indication of a negative value for NON-ALGAL OUPTK; negative values are
assumed to be zero for the estimation of annual NON-ALGAL OUPTK.
-92-
Table 17.
Estimates of seasonal sediment-associated mean microalgal biomass
and aicroalgal production in Netarts Bay at the SILT site.
The
tidal levels are 0.5 m, 1.0 m and 1.5 m above MLLW.
Variable and
method of calculation are the same as described for Table 15.
BIOMASS
GPP
5.81
14.50
5.99
NON-ALGAL
OUPTK
RESP
NPP
21.46
14.20
13.65
19.91
13.28
12.99
1.55
0.92
0.66
28.85
39.66
35.16
8.94
26.38
22.17
4.33
4.14
5.68
20.60
10.88
22.86
13.59
7.83
15.15
7.01
3.05
7.71
46.98
18.15
34.44
33.39
10.32
19.29
2.21
2.37
3.50
11.32
27.63
14.32
6.96
16.82
8.89
4.36
10.81
5.43
25.84
49.25
56.96
18.88
32.43
48.07
3.42
3.33
4.84
10.64
11.02
37.08
9.04
7.74
19.23
1.60
3.28
17.85
28.79
35.96
48.06
19.75
28.22
28.83
3.94
6.09
5.00
64.02
63.73
87.91
49.50
45.67
56.26
14.52
18.06
31.65
130.46
162.83
174.62
80.96
117.16
118.36
OIJPTK
-93-
presented in a later section of this report (page 109).
In several cases for
the SAND and FINE SAND sites, the latter assumption generated a negative value
for non-algal oxygen uptake, indicating that microalgal respiration was
probably less than the assumed 29%.
In general, the annual rates of gross primary production for the three
intensive study sites were well within the range of values reported in the
literature for similar habitats (Table 18).
Annual gross primary production
varied from 74.86 to 204.47 g C m2, both extremes occurring at the SAND
site.
Maximum microalgal production at the SAND and FINE SAND sites occurred
in the summer at tidal levels where sporelings of Enteromorpha were prominent.
Production at the SILT site, where Enteromorpha did not occur, was less variable with the maximum in the fall at 1.5 m above MLLW.
This site also exhib-
ited an unusually high mean biomass at 1.0 m above MLLW during the winter when
gross primary production was a little below the average for all seasons.
Possible explanations for this inconsistency include:
(1) an underestimation
of net primary production either by an over estimation of microalgal respir-
ation or by an under estimation of gross primary production; (2) over estimation of microalgal biomass; and (3) microalgal heterotrophy.
If rates of
gross primary production were markedly higher on exposed sediment than on
inundated sediment, our method of measurement could have provided an underestimate for this variable.
Furthermore, heterotrophic growth of sediment-
associated microalgae has been reported by Admiraal and Peletier (1979),
Jorgensen et al. (1980), McLean et al. (1981), and Hellebust and Lewiri
(1977).
In particular, the work of Admiraal and Peletier (1979) suggest that
at least some diatoms associated with fine sediment particles can grow almost
as rapidly in the dark as in the-light if a suitable organic substrate is
available.
The potential of the diatom flora at the SILT site for hetero-
-94-
Table 18.
Annual rates of benthic microalgal primary production reported in
selected studies.
Rate
Study
Location
(g c m2 yr')
1.
Steele & Baird (1968)
beach sand
4-9
2.
Pomeroy (1959)
Georgia salt marsh
200
3.
Grontved (1960)
Danish fjords
116
4.
Cadee & Hegeman (1974)
Western Wadden Sea
100
5.
Cadee & Hegeman (1977)
Western Wadden Sea
29-188
6.
Pamatmat (1968)
False Bay, San Juan Island
143-226
7.
Gallagher & Daiber (1974)
Delaware salt marsh
8.
Marshall et al. (1971)
Southern New England
100
9.
Leach (1970)
Northern Scotland mudflat
31
Riznyk & Phinney (1972)
Yaquina estuary, Oregon:
Southbeach (sandy silt)
Sally's Bend (fine silt)
10.
Netarts Bay:
SAND
FINE SAND
SILT
38-99
275-325
0-125
129*
153*
72*
*Values represent the mean of values for the three tidal levels (0.5 in,
and 1.5 in above MLLW).
1.0 m,
-95-
trophic growth is unknown.
However, the survival of diatoms at 18 cm below
the surface of the sediment was reported by Riznyk (1969) for assemblages in
Yaquina Bay, suggesting the possibility of heterotrophic nutrition or a
temporary decrease in metabolic rate during burial (McIntyre et al., 1970).
Sources of carbon for non-algal community oxygen uptake probably included
both algal and non-algal organic matter.
At the SAND, FINE SAND, and SILT
sites, 100%, 50%, and 20%, respectively, of the carbon for metabolism could
have been derived from microalgae which were available during the entire year.
The remaining carbon was probably supplied by detrital sources from other
areas.
Other studies have found that detritus is a major source of carbon to
estuarine secondary production (Pomeroy et al., 1977; Tenore, 1977).
of detrital carbon to Netarts Bay included Enteromorpha, Zostera
fungi, animals, and microalgae.
,
Sources
bacteria,
There did not appear to be major contribu-
tions of carbon from the marsh because of the limited export of particulate
matter from the area.
However, studies have shown that some of this high
marsh production may be exported as energy to the intertidal habitats in the
form of dissolved reduced inorganic sulfur compounds and used chemotrophically
by anaerobic organisms while their carbon source is carbon dioxide (Howarth
and Teal, 1979).
The contribution to net primary production by Enteromorpha (2800 g
c m2 yr1) was a large seasonal input of organic matter into Netarts Bay,
especially during the summer and fall.
Similar patterns of Enteromorpha
growth were observed in other estuaries (Conover, 1958; Nienhuis, 1970).
By
comparison, microalgae supplied a much smaller proportion of organic matter to
the total net primary production of algae in the bay (15 to 65 g C m2 yr).
However, this microalgal contribution is also important and represents a
significant source of food which is available throughout the year for benthic
organisms (Baillie and Welsh, 1980; Ribelin and Collier, 1980).
In conclusion, it was evident that microalgal production and biomass in
Netarts Bay was controlled by daylength, temperature, water currents, sediment
moisture and stability, animals, and macrophyte cover.
Nutrients did not
appear to limit microalgal growth, apparently because of the abundance of
nutrients in the intertidal sediments (Admiraal, 1977b, d; Cardon, 1981).
The
possibility of heterotrophic growth in microalgae was suggested by the
presence of relatively high biomasses of microalgae during periods of low net
primary production in the winter on sediment with high concentrations of
organic matter.
The sediment communities at the FINE SAND and SILT sites
obtained at least half or more of their carbon from detrital sources other
than in situ microalgal net primary production.
However, Enteromorpha and
Zostera production in the bay provided large supplies of carbon for sediment
community metabolism during the summer and fall.
II.
Experimental Studies of Estuarine Benthic Algae
Laboratory studies were designed to investigate relationships between
sediment-associated estuarine algae and physical factors affecting their
growth.
Specific objectives of this research included:
(a) the determination
of the relationship between light intensity and gross photosynthesis in
assemblages of sediment-associated algae; (b) the determination of the relationship between temperature and community metabolism in sediment-associated
algal assemblages; and (c) the determination of the relationships between
biomass and metabolic rates and between biomass and chlorophyll a in populations of epipelic diatoms and macroalgae isolated from sediment-associated
-97-
algal assemblages.
Experiments corresponding to these objectives were con-
ducted at the Oregon State University Marine Science Center (Newport, Oregon)
and nearby tidal flats in Yaqunia Bay.
Results from these experiments were
used to help understand mechanisms that accounted for the production dynamics
of algal assemblages in Netarts Bay and for the estimation of parameters
compatible with our structural model of the Algal Primary Production subsystem.
Yaguina
Yaquina Estuary (44°35' N;
124°04' W) drains 656 km2 of the Coast
Range (Fig. 21) and is Oregon's fifth largest estuary, with a surface area of
1583 hectares, of which 548 hectares is tideland and 1035 hectares is subtidal.
The estuary is subjected to mixed semi-diurnal tides and is classified
as a partly-mixed system in the winter and spring and a well-mixed system
during the summer and fall.
Maximum tidal range is 3.0 m.
Mean low water
(MLW) and the mean high water (MHW) are 0.5 m and 2.0 m above the mean lower
low water datum (MLLW), respectively.
Daylight hours in Newport vary from
8.5 perday in June to 15.5 per day in December.
estuary is complex.
The salinity pattern in the
In the summer, upwelled bottom water from off the Oregon
coast combines with insignificant fluviatile input to account for a relatively
high salinity (33 to 35 0/00) in Yaquina Bay.
In the winter, high freshwater
discharge is responsible for salinities as low as 8 0/00 at the Marine Science
Center during low tide.
During a complete tidal cycle, 707 of the water in
the bay is exchanged with ocean water (Goodwin et al., 1970).
During an
-98--
OREGON
I
OCEAN
I
YAQLJ/NA BA
:::..
,,
-------
%
OREGON
Figure 21.
I
. Y::
-
o
:
METERS
gri'
.
5f
:
.
..
'-
.
:.
..
wg
/
...
.
..
-\
.
.
--I
S
I
- --
N
Map of Yaquina Bay with arrows indicating location of intensive
study sites.
S.
entire year, water temperature over the sediment flats usually ranges from 6°C
to 20°C, and the air temperature over exposed sediment flats ranges from 0°C
to 30°C.
Methods
1.
Primary Production
Gross primary production and community oxygen uptake were estimated in
the laboratory from oxygen measurements in stirred, light and dark chambers
designed to hold intact cores of sediment.
Between March and September,
measurements were made in plexiglas chambers which were 32.5 cm long and had
an internal diameter of 14.5 cm (Fig. 22).
Each chamber held three intact
sediment cores, and these cores were 5 cm deep with a total sediment surface
area of 136.08 cm2.
The chambers were filled with 5.7 1 of filtered seawater,
sealed and placed into a water bath.
through tygon tubing by a pump.
Water in each chamber was circulated
Rates of oxygen evolution were based on
measurement periods of 0.5 to 1.0 hour between initial and final readings.
Measurements of dissolved oxygen were made polarographically with an Orbisphere
salinity-corirected dissolved oxygen system by inserting the oxygen
probe into a pot connected to the water circulation line.
Between October and
May, estimates of primary production were made in vertical plexiglas chambers
described in an earlier section of this report (Fig. 9 and page 44); the
methods were essentially the same as those used for the field work.
Rates of net community production or oxygen uptake were measured when
either type of chamber was exposed to light or darkened by covering with a
sheet of black plastic, respectively.
All chambers were preiricubated in the
dark for 1.0 hour before incubations under sunlight or incandescent and cool-
IJ!
- -
r
..
COOLING
COILS
PUMP
PLEXIGLAS CHAMBER
FOR 02 METABOLISM
CHAMBER
02 PROBE PORT
BUNG
RUBBER
0/
/
ATER FLOW
GASKET
- -..--'-
L.....
.
.
I
_i
DIagram of a plexiglas chamber from measuring oxygen productl9n and uptake of intact
sediment cores and macroalgae.
--
- - -
FJgire 22.
I
PVC
HOLDER CORER
CORER
SEDIMENT
ALGAE AND
-
-10 1-
white flourescent lamps.
Fiberglass screening was used as a neutral density
filter to reduce light Intensity when required.
Simultaneous incubations of
intact sediment cores in both types of chamber indicated that there were no
significant differences in primary production attributable to chamber type.
Computations of gross primary production from the oxygen data were made
following the same procedure described in an earlier section (see page 47 of
this report).
2.
Biomass
Microalgal biomass expressed as the concentration of chlorophyll a was
determined following the procedure described earlier on page 47 of this
report.
Macroalgal biomass samples were rinsed in fresh water, weighed, dried
at 70°C for 48 hours, and reweighed.
Dried samples were ignited in a muffle
furnace at 450°C for 24 hours and reweighed to estimate weight of organic
matter.
The chlorophyll a concentration in macroalgae was determined by the
method described for uiicroalgae using approximately 1.0 g wet weight of algae
per sample.
Carbon content was estimated by multiplying the weight of organic
matter by 0.5 (Vollenweider, 1974).
3.
Isolation of Diatom Assemblages
Motile, epipelic diatoms were isolated from sediment samples obtained
each season during an entire year at intensive study sites in Yaquina Bay
using the method of Jonge (1980).
Approximately 1000 cm3 of the top cm of
sediment were taken from the field and transported to the laboratory.
This
sediment was mixed with 100 ml of sand-filtered, UV-treated seawater (30 to
33 0/00 salinity) and spread out in a shallow tray, 40 by 50 cm.
quartz sand (125 to 250
Clean white
m particle diameter) was spread over the sediment in
-102-
a 1 nun layer, and three layers of lens tissue were placed over the sand and
the sediment.
The entire tray was covered with clear plastic and incubated
for 36 hours at 15°C and a light intensity of 150 11E m2 sec1
After the incubation period, the lens tissue was lifted off the sediment
and mixed with 500 ml of sand-filtered, UV-treated seawater.
The mixture was
filtered through four layers of 2.5 mm thick foam plastic and then through a
55
m Nitex(u mesh net.
The foam plastic filtered Out lens tissue fibers, and
the net filtered out small animals.
Microscopic inspection confirmed that the
light brown-colored suspension contained primarily diatoms and few bacteria or
flagellates.
The diatom suspension obtained from the isolation procedure was used to
establish relationships between primary production and chlorophyll a, organic
matter and chlorophyll a and for measurements of algal respiration.
Four
replicate 50-nil screw-cap test tubes with a diatom sample were incubated for
0.5 hr at a light intensity of 210 1E m2 sec, a temperature of 14°C, and a
salinity of 30 to 33
/oo.
under similar conditions.
Samples also were incubated in the dark for 0.5 hr
Measurements of oxygen concentration and calcula-
tion of production were performed as described above.
After these measure-
ments, 50 ml samples of diatom suspensions were filtered on pre-ashed glass
fiber filters, and chlorophyll a was extracted from four filters in acetone
using methods described above.
Also, four filters were dried at 70°C for
24 hrs and reweighed to determine dry weight.
Then these filters were ignited
in a muffle furnace at 450°C for 24 hr and reweighed to determine weight of
organic matter.
Carbon content was estimated by multiplying the weight of
organic matter by 0.5 (Vollenweider, 1974).
-103--
4.
Physical Variables
Light intensity was measured in -'E m2 sec1 photosynthetically active
radiation using a Licor® quantum meter.
metal or thermistor probes.
Temperature was measured using bi-
A temperature-compensated AO Goldberg® refracto-
meter was used to measure salinity.
Results
1.
Experiments With Intact Sediment Cores
The relationship between light intensity and gross primary production of
intact sediment cores was investigated in March, August, and September, 1980
(Figure 23).
Experiments A, B, and C were conducted outdoors under natural
sunlight and fiberglass screens, while experiment F was performed in the
laboratory under a fluorescent-incandescent lamp fixture and fiberglass
screens.
Mean microalgal biomasses, expressed as mg chlorophyll a m2 in the
top cm of sediment, for two replications (i.e., two respirometers with intact
sediment cores) during experiments A, B, C, and F were 134, 199, 213, and 115,
respectively.
Data from the experiments suggested that the relationship between light
intensity and gross primary production was approximately linear at intensities
between zero and250 PE m2 sec, except in experiment C where the linear
segment was between zero and about 150 UE m2 sec.
linear segment from zero to 248
The equation for a
'E m2 sec' estimated from data pooled for
all four experiments is
GPP = 0.59 I,
where GPP is the rate of gross primary production expressed as mg C m2 hr
and I is the light intensity.
To estijnate the asymptotic maximum rate (max
4Il
L.
-
200
0
0
(I)
(I)
a-
>-
a-
a::
50
z'50
0
I0
0
0100
0
E
tJ
-c
250
[SJ
Figure 23.
400
600
s
800
,,
Relatlonntiip between grons primary production and light
Intensity. Data correspond to experiments A (open squares),
B (triangles), C (solid squares), and F (hexagons). See
text (or curve fitting procedure.
LIGHT INTENSITY (tE m2 sec')
200
'I.I.IsJ
p1
-105-
and the shape of the curves above 248 UE m2 sec, several functions were
examined for experiments A, B, and C.
The rectangular hyperbola, a function
commonly used as a model of photosynthesis-light relationships (Lederman and
Tett, 1981), generated 'max estimates of 284 (A), 269 (B), and 172 (C) g
C m
hr1, values that were inconsistent with the distribution of the data
points.
This model forced the curve through the origin and, in this case,
provided relatively high estimates of
'max
A more satisfactory estimate was
obtained by the exponential model:
GPP=B0-B2e
where
-B2 I
is equal to 1'max
Curves generated by this function for experiments
A, B, and C are plotted in Figure 23.
The curves for experiments A and B
intersect the linear segment at 267 and 260 3iE m2 sec, while the curve for
experiment C does not intersect the linear segment; the latter curve is ter-
minated at an intensity of 157 liE m2 sec.
Estimates of
max for experi-
ments A, B, and C from the exponential model are 233, 181, and 136 mg C m2
hr, respectively.
Data in Figure 23 indicate that the onset of light saturation of photo-
synthesis (1k) occurs between 200 and 400 jE m2 seC'.
Here
is defined as
the light intensity at which extrapolations of the linear segment and the
light-saturated region of the GPP-intensity curve intersect (Talling, 1957).
For our purposes, 1k = Pm/O.S9, where
max is estimated by the exponential
model and 0.59 is the slope of the linear segment.
experiments A, B, and C are 395, 307, and 231
Therefore, 1k values for
E m2 sec, respectively.
The effect of temperature on rates of gross primary production and oxygen
uptake in assemblages of sediment-associated microalgae was investigated in
-106-
May, 1981 (Tables 19 and 20).
Each experiment consisted of three replica-
tions, i.e., three respirometers with intact sediment cores; and sediment
cores for each replication were collected from two intertidal levels in
Yaquina Bay:
1.9 m and 1.0 m above MLLW.
The mean chlorophyll a concen-
tration in the top cm of the sediment cores was 151 mg m2 and the corre-
sponding standard deviation was 21.7 mg m2.
Water temperature in Yaquina Bay
during April and May varied between 11° and 14°C.
The temperature range under
investigation was from 7°C to 17°C, a range between the maximum and minimum
annual values recorded for the bay.
The light intensity during the primary
production measurements was 600 .iE if2 sec, an intensity well above the
values determined during the experiments illustrated in Figure 23.
Data are
reported as hourly rates and Q10 values, where
10/(t -t )
10-
r2r1
The temperature coefficient (Q10) is a multiplier that predicts the rate for a
10°C change in temperature, t2 and t1 are the upper and lower temperatures of
the range under consideration, and r2 and r1 are metabolic rates corresponding
to t2 and t1, respectively.
Rates of gross primary production varied betwen 24.68 and 252.30 mg C if2
hr
19).
depending on temperature, experiment number, and replication (Table
Therefore, estimates of Q10 at light saturation were based on a set of
samples representing a wide range of photosynthetic capacities.
The mean Q10
value for three replications of each of four experiments (n = 12) was 2.05
with a standard error of 0.15.
There was no significant correlation between
the mean rate of gross primary production for a particular replication and its
Experiment
Table 19.
36.85
85.04
14.0
7.0
16.0
8.0
15.0
181.65
127.00
151.92
144.12
162.13
+1.9
+1.9
49.35
24.68
246.63
145.52
175.76
141.74
119.06
7.0
154.02
+1.1
139.85
2.69
2.53
2.83
45.36
52.43
55.52
52.43
32.90
1.59
40.10
33.93
1.86
100.16
113.39
102.05
2.43
51.03
48.19
2.30
249.47
252.30
1.68
99.22
249.47
2.24
1.51
164.42
1.42
147.41
1.46
113.39
107.72
107.72
GPP
17.0
Q10
152.52
GPP
76.54
Q10
8.0
GPP
137.51
Q10
+1.1
GPP
Temperature
Biomass
Level
2
Mean
Tidal
Replication
Mean
2.04
2.45
2.25
1.46
Q10
Temperature range was from 7°C to 17°C; salinity was 30 0/00, and light
Mean biomass for three replications at each temperature is
intensity was 600 liE m2 sec. Data corresponds to samples from 1.9 m and 1.0 m above MLLW.
expressed as mg chlorophyll a n12.
values for intact sediment cores from Yaquina Bay.
The rate of gross primary production (mg C m2 hr') at different water temperatures and corresponding Q10
-107-
4
3
I
Experiment
Table 20.
+1.9
+1.9
+1.1
+1.1
Level
Tidal
30.67
54.52
17.0
7.0
14.0
152.52
154.02
181 .65
8.0
15.0
162.13
25.95
11.12
23.85
16.0
151 .92
144.12
6.81
7.0
127 .00
40.88
17.04
8.0
137.51
OUPTK
Temperature
Bloma ss
Mean
1
3.36
4.03
2.27
2 .64
Q10
29.66
37.07
29.66
22.24
1.15
30.67
27.26
6.81
6.81
4.67
61.33
54.52
40.89
37.48
37.48
1 .71
3
OUPTK
61 .33
2.36
Q1
44.29
20.44
0 UPTK
2
Replica t ion
1.38
5.32
1.78
1.73
Q10
30.89
21 .01
27.26
6.81
56.79
36.35
48.84
24.99
OUPTK
Mean
1.96
4.67
1.92
2.24
Q10
The rate of oxygen uptake (OUPTK) expressed as carbon equivalent (mg C m
hr') at different water temperatures
Mean biomass for three replications at
and corresponding Qio values for Intact sediment cores from Yaqulna Bay.
each temperature Is expressed as mg chlorophyll a m2. Temperature range was from 7°C to 17°C; salinity was
30 0/00. Data corresponds to samples from 1.9 m and 1.0 m above MLLW.
-108-
-109-
corresponding Q10 value (r = -0.08 with 10 d.f.).
However, the mean Q10 value
was significantly higher for samples obtained at + 1.9 m above
samples obtained at + 1.0 m above
MLLW
MLLW
than for
(t = 22.27 with 10 d.f.); the corre-
sponding means were 2.23 and 1.87, respectively.
Temperature coefficients for rates of oxygen uptake in the dark were more
variable than values associated changes in the rate of gross primary production (Table 20).
The mean Qç value for measurements of oxygen uptake (n =
12) was 2.70 with a standard error of 0.39.
There was a significant negative
correlation between the mean uptake rate for a replication and the corresponding Qi
value (r = -0.72 with 10 d.f.).
samples from 1.9 m above
samples from 1.0 above
MLLW
MLLW
Also, the mean Q10 value for
was significantly higher than the mean for
Ct = 10.04 with 10 d.f.); these means were 3.32
and 2.08, respectively.
2.
Experiments With Isolated Epipelic Diatoms
The procedure for isolating living epipelic diatoms from sediment samples
provided the opportunity to estimate some useful ratios for sediment-associated microalgal assemblages.
The ratios of interest were (1) biomass as ash-
free dry weight to chlorophyll a (AFDW/CHLOR); (2) gross primary production to
chlorophyll a (GPP/CHLOR); and (3) net primary production to gross primary
production in the light (NPP/GPP).
The ratio AFDW/CHLOR provided a basis for
estimating autotrophic biomass in sediment-associated microalgal assemblages
when such assemblages consist primarily of diatoms, while NPP/GPP provided
corresponding estimates of respiratory losses.
Results of experiments with isolated epipelic diatoms are presented in
Tables 21-23.
AFDW/CHLOR values varied from 107.55 to 254.98 with a mean for
-110-
all experiments of 166.98 and a standard error of 8.20 (Table 21).
The lowest
mean value for a particular experiment was obtained during January, and the
most variation among replications occurred in an experiment conducted in
February.
Estimates of GPP for the calculation of GPP/CHLOR and NPP/GPP were
based on the assumption that respiration in the dark was equal to respiration
in the light.
GPP/CHLOR values were considerably higher than values obtained
for intact sediment cores (Tables 14 and 22) and were more similar to values
reported for algal cultures and natural populations of phytoplankton (See
Table 17 in Parsons et al., 1977).
The mean value for seven experiments
(28 replications) was 5.12, and the associated standard error was 0.40.
The
mean ratio of net primary production to gross primary production for seven
experiments was 0.71 (Table 23) indicating that respiration was approximately
29% of GPP for an equivalent period of time.
3.
Experiments With Isolated Macroalgae.
Rates of primary production and biomass for sediment-associated macroalgae are summarized in Table 24.
Three species of algae were studied:
Enteromorpha prolifera (Mull.) J.Ag.; Ulva expansa (Setch.) S.&G.; and
Gracilaria verrucosa (Huds.) Papenf.
Rates of respiration per gram dry weight
were similar for all three species, while rates of gross and net primary pro-
duction were higher for Enteromorpha and Ulva than for Gracilaria.
Maximum
biomass at the intensive study sites and chlorophyll a concentration per gram
dry weight were much higher for the green algae.
However, gross primary
production per mg chlorophyll a was higher for Gracilaria than for Ulva and
Enteromorpha.
Mean net primary production for Enteromorpha, Ulva, and
Gracilaria, calculated from the specific rate and biomass estimates was 4.7,
-111-
Table 21.
Ratio of blomass expressed as ash-free dry weight to chlorophyll a concen-
tration in assemblages of epipelic diatoms isolated by the lens paper
method from intertidal sediment samples from Yaquina Bay.
Data include
the ratio for each replication and the mean ratio and standard error for
each experiment.
Replication
Date of
s.E.
Experiment
10/1/80
209.96
192.85
177.42
177.25
189.37
7.78
10/28/80
176.22
189.86
186.16
189.11
185.34
3.14
1/21/80
107.55
132.44
135.25
122.76
124.50
6.25
2/26/80
113.51
254.98
161.70
126.22
164.10
31.96
4/2/80
108.20
190.17
143.23
168.84
171.62
10.51
166.98
8.20
Pooled
-112-
Table 22.
Ratio of gross primary production (mg C hr) to chlorophyll a (mg) in
assemblages of epipelic diatoms isolated by the lens paper method from
intertidal sediment samples from Yaquina Bay.
The light intensity,
temperature, and salinity during the experiments were 21O1 E m2 sec,
Data include the ratio for
14°C, and from 30 to 33 0/00, respectively.
each replication and the mean ratio and standard error for each experimen t.
Date of
Replication
Experiment
S.E.
2/26/81
5.58
5.47
6.91
6.48
6.11
0.35
3/14/81
2.29
2.43
2.43
3.54
2.67
0.29
4/2/81
3.07
3.49
2.86
3.18
3.15
0.13
5/9/81
3.13
2.23
2.78
4.17
3.08
0.41
10.49
7.37
6.44
7.01
7.83
0.91
11/9/81
6.91
6.40
6.43
6.92
6.67
0.14
12/11/81
6.27
5.57
6.10
7.46
6.35
0.40
5.12
0.40
10/30/81
Pooled
-113-
Table 23.
Ratio of net primary production to gross primary production in assemblages
of epipelic diatoms isolated by the lens paper method from intertidal
sediment samples from Yaquina Bay. The light intensity, temperature, and
salinity during the experiments were 210U E m2 sec1, 14°C, and from 3033 0/00, respectively. Data include the ratio for each replication and
the mean ratio and standard error for each experiment.
Replication
Date of
S.E.
Experiment
2/26/81
0.86
0.86
0.87
0.86
0.86
0.00
3/14/81
0.41
0.50
0.50
0.69
0.53
0.06
4/2/81
0.88
0.87
0.88
0.86
0.87
0.00
5/9/81
0.30
0.40
0.55
0.30
0.39
0.06
10/30/81
0.80
0.73
0.81
0.82
0.79
0.02
11/9/81
0.81
0.76
0.71
0.74
0.76
0.02
12/11/81
0.82
0.76
0.79
0.74
0.78
0.02
0.71
0.03
Pooled
-114-
Table 24.
Biomass and rates of primary production for sediment-associated macroalgae
in Yaquina Bay.
Species include:
and Gracilaria verrucosa.
Enteromorpha prolif era, Ulva expansa,
Measurements were made at 13° to 15°C, a salin-
ity of 30 0/00, and a light intensity of 600
include:
E m2 sec. Variables
respiration (RESP), net primary production (NPP), gross primary
production (GPP), dry weight (DW), ash-free dry weight (AFDW), carbon (C)
calculated as AFDW x 0.5, and chlorophyll a concentration (CHLR).
Values
are expressed as means of six replications with corresponding standard
errors (SE).
Biomass values correspond to the period of maximum standing
crop which was from June to August for Enteroinorpha, July to September for
Ulva, and March to May for Gracilaria.
Ulva
Enteroinorpha
Variable
S.E.
S.E.
1.
RESP (mg C g DW'
2.
3.
GPP (mg C g DW1
4.
DW
5.
hr)
Gracilaria
S.E.
1.4
0.3
1.4
0.4
1.0
0.2
NPP (mg C g DW' hr')
9.5
1.2
10.3
0.4
7.6
1.2
hr)
10.9
0.9
11.7
0.8
8.5
1.1
497.8
69.6
411.9
65.9
19.5
2.2
AFDW (g f2)
323.6
48.5
267.7
25.2
13.1
2.2
6.
C (g
161.8
24.3
133.9
8.03
6.5
1.1
7.
CHLR/DW
2.5
0.0
1.9
0.0
0.9
0.1
8.
CPP/CHLR (mg hr' mg)
4.4
0.4
6.2
0.5
9.4
0.9
9.
Daylight NPP/GPP
0.87
0.04
0.88
0.02
0.88
0.03
*Npp
(g m2)
if2)
(mg g)
(g C m2 hr)
*Estimated from 2 and 6
4.7
4.2
0.2
-115-
4.2, and 0.2 g C m2 h, respectively.
Light saturation of macroalgal photo-
synthesis was similar to that for rnicroalgae (200 to 400 -IE m2 sec).
No
inhibition of photosynthesis was noted at full sunlight (1500 to 2000 1E m2
sec1), although some bleaching of thalli was observed in the field when
macroalgae were exposed to full sunlight at low tide.
Interpretation of Experiments
Results of the experiments relating gross primary production to light
intensity indicated that the sediment associated microalgal assmeblages
reached their light-saturated rate at an intensity between 10% and 20% of the
intensity at full sunlight (1500 to 2000 1E m2 sec).
Similar results were
reported by Admiraal (1977) and Colijn and van Buurt (1975).
photosynthesis was observed at 950
No inhibition of
liE m2 sec, suggesting that the assem-
blages, which consisted primarily of motile epipelic diatoms, were able to
make vertical adjustments in the sediment that optimized growth and survival.
Since the light intensity is about 1% of the surface intensity at a depth of
2 mm in the sediment (see page 58 of this report), such vertical adjustments
in position require relatively little time.
For example, a diatom moving at
mean speed of 10 In sec', a reasonable estimate for motile forms (Harper,
1977), can descend from the sediment surface to a depth of two 2 mm in about
3 mm.
Light-saturated rates of primary production for experiments A, B, and C
apparently were not determined by the chlorophyll a concentration in the top
cm of sediment, as the lowest rate (experiment C) was found for the assemblage
with the highest chlorophyll concentration.
The chlorophyll a concentrations
in the experimental sediment cores were relatively high during all three
-116-
experiments, considerably higher than mean concentrations found between 0.5 m
and 1.5 in above NLLW at the three intensive study sites at Netarts Bay (Table
6).
Therefore, it is possible that microalgal assemblages in tidal flats
under the influence of marine water can realize their maximum productive
capacity at chlorophyll a concentrations below 100 mg ui2.
Also, there is a
strong possibility that the measurable chlorophyll in the top cm of sediment
is not all involved in the photosynthetic process, either because of burial
below the 2 mm level or because the analytical method fails to discriminate
between chlorophyll a and chlorophyllides.
A recent investigation of benthic
autotrophy in the Columbia River estuary revealed a linear relationship
between gross primary production and chlorophyll a concentration in the top
cm up to concentrations as high as 400 mg ni2 (Table 14).
However, the max-
imum rate of gross primary production measured during the Columbia River study
was 199 mg C m2 hr', a value less than the estimated
iment A.
value for exper-
These data indicate that sediment chlorophyll in the lower Columbia
River is less active in the photosynthetic process than that in Netarts Bay or
Yaquina Bay.
There is no clear explanation for this difference, although the
study areas on the Columbia River are subjected to severe physical stress
during periods of high freshwater discharge.
tn general, an increase in temperature stimulated community oxygen uptake
more than gross primary production.
Similar observations were reported by
Duff and Teal (1965), Pamatmat (1968), and Davies (1975).
Phinney and
Mclntire (1965) found that temperature can affect the rate of photosynthesis
at light saturation in lotic periphyton assemblages.
The Q10 value of 2
reported for the lotic assemblages was remarkably similar to the mean value of
2.05 obtained for the sediment-associated assemblages from Yaquina Bay.
How-
-117-
ever, it is doubtful that temperature fluctuations accounted for a change in
max from 136 mg C m2 hr
A).
(experiment C) to 233 mg C m2 hr
(experiment
Therefore, differences in 1'max were apparently related to differences in
the physiological state of the experimental assemblages, although mechanisms
responsible for this physiological variation are unclear.
From the experimental work and observations at Netarts Bay and the
Columbia River Estuary,
max
for sediment-associated diatom assemblages under
the most favorable conditions for growth, i.e., optimum resources, tempera-
ture, and biomass, must be in the neighborhood of 240 mg C m2 hr1.
If the
assemblages are exposed to an average input of light energy equivalent to
10 hr day
above the saturation intensity for photosynthesis, the upper limit
of gross primary production, i.e., the autotrophic potential for such communi-
ties, is approximately 900 g C m2 yr'.
Mclntire (1973) estimated that
max
under optimal conditions for lotic periphyton was about 1 g 02 m2 hr.
Assuming a P.Q. of 1.2, the autotrophic potential for epilithic periphyton
in streams is estimated to be 1,150 g C m2 yr. Values reported in the
literature for sediment associated microalgal assemblages are usually about
25% or less of the estimated upper limit of 900 g C m2 yr
(Table 18).
Therefore, factors such as temperature, turbidity, sediment instability,
animal activity, toxic metabolic byproducts, and nutrient limitation apparently prevent these assemblages from realizing their autotrophic potential.
However, in the case of Yaquina Bay, some recent experiments indicate that
sediment associated microalgal assemblages are not nutrient limited (Cardon,
1981).
The mean ratio of gross primary production to the concentration of
chlorophyll a in the top cm of sediment for the experimental work with intact
cores was 0.66 mg C hr
mg. This value was similar to the mean value found
-118-
for the pooled field data from Netarts Bay (0.48 mg C hr' mg) and to values
found in other studies of sediment-associated microalgae (Colijn and van
Buurt, 1975; Admiraal, 1977).
The mean value for this ratio for pooled
samples from the Columbia River estuary was 0.31 m C hr
mg' (Table 14),
indicating that the relationship between primary production and chlorophyll
concentration is variable and may be an unreliable basis for predicting
production dynamics in a particular estuary.
Gross primary production of diatom assemblages isolated from the sediment
was very similar to the gross primary production reported for phytoplankton
assemblages (Steeman Nielsen and Hansen, 1959), indicating physiological
similarities in photosynthesis between benthic and pelagic diatoms.
Similar
values have been obtained for berithic diatoms grown in liquid pure culture
(Admiraal, 1977a).
Apparently, conditions in the sediment prevent epipelic
diatoms from attaining photosynthetic rates that they can realize isolated in
a liquid suspension.
Hourly net primary production averaged 71% of hourly
gross primary production for isolated diatoms, assuming the respiratory rates
in the light and dark were equal.
Colijn and van Buurt (1975) measured net
primary production of isolated diatoms, but their measurements did not include
an estimate of respiration.
Such information is useful in field studies when
it is desirable to partition algal respiration from community oxygen uptake,
as community oxygen uptake includes microbial, plant, and animal respiration
as well as chemical oxygen uptake.
Unfortunately, there is no satisfactory method for determining the ratio
of net primary production to gross primary production in assemblages of sediment-associated microalgae.
Our tentative estimate of 71% from suspensions of
isolated epipelic diatoms may have been affected by bacterial contamination
and the change from sediment contact to conditions in a culture vessel.
-119-
Although bacteria were not observed by direct microscopic examination of the
isolated suspensions, they were probably responsible for some oxygen uptake
Moreover, the availability of oxygen is undoubtedly
during the experiments.
variable among the different sediment types and between a given sediment type
and conditions in the culture vessel, differences that limit the use of the
laboratory results for indirect estimates of net primary production and algal
respiration in the field.
Pomeroy (1959) also estimated microalgal respira-
tion by an indirect method and found net primary production to be not less
than 90% of gross primary production.
In our experiments with macroalgae,
rates of respiration were about 15% of the rate of gross photosynthesis for an
equivalent period of time.
Estimates for macroalgae were probably more reli-
able than those for the microalgal assemblages, as the ratio of macroalgal
biomass to the biomass of bacterial contaminants was relatively large and
experimental conditions for the macroalgae were more compatible with the
natural conditions in the estuary than the environment of a culture vessel.
The measurement of the ratio of biomass (ash-free dryweight) to chiorophyll a concentration in isolated assemblages of epipelic diatoms provided a
basis for estimating autotrophic biomass in sediment-associated microalgal
assemblages when diatoms dominated the flora.
Assuming one-half of the
biomass was carbon, the mean value for this ratio was approximately 84 mg
C mg
chlorophyll a.
Jonge (1980) reported values for the Ems-Dollard
estuary that ranged from 10.2 to 153.9 mg C mg1, and found that the ratio
varied seasonally and from year to year.
Mean values for three successive
years were 40.3, 41.2, and 61.4 mg C mg, all of which are less than the mean
estimated for the assemblages from Yaquina Bay.
Howe er, Jonge's values were
based on direct measurements of organic carbon, while in the research reported
-120-
here, biomass was measured as the weight lost after ignition, and carbon was
estimated indirectly.
In any case, estimates of autotrophic biomass in the
sediment by the multiplication of chlorophyll concentrations by a biomass:
chlorophyll ratio will be affected strongly by the physiological state of the
biomass that was involved in the experimental determination of the ratio.
Therefore, it is desirable to determine the ratio during the season when the
biomass estimates are required, and to measure the biomass of the experimental
assemblages in the same units needed for the field estimates.
Ratios of gross primary production to chlorophyll a concentration for
sediment associated macroalgae were similar to values obtained for isolated
diatom assemblages, but from 10 to 20 times higher than corresponding values
for micralgae in intact sediment.
Production of Enteromorpha and Ulva in
Yaquina Bay and Netarts Bay was higher than corresponding values reported for
o'ther estuaries (Littler et a].., 1979; King and Schramm, 1976; Buesa, 1977;
Conover, 1958), although specific rates of photosynthesis (i.e., the rate per
unit of biomass) in the Oregon plants were similar to rates found for material
from other geographical locations.
Production estimates obtained during this
study for Gracilaria were similar to values reported in the literature
(Lapointe et al., 1976; Vawes et a].., 1978).
Also, light saturation of macro-
algal photosynthesis was similar to that for microalgal photosynthesis and
that measured in other studies (King and Schramm, 1976; Dawes et a].., 1978;
Ramus and Rosenberg, 1980).
No inhibition of photosynthesis at full sunlight
was observed.
The net daily primary production of sediment-associated algae was estimated to compare the productive potential of green macroalgae, red macroalgae,
and sediment-associated microalgae (Table 25).
The daylengths corresponded to
-121-
Table 25.
Daily net primary production of sediment-associated algae in
Enteromorpha prolifera, Ulva expansa,
Yaquina Bay. Algae are:
Gracilaria verrucosa and sediment-associated microalgae (preValues are estimated from Tables 23 and 24,
dominately diatoms).
and from field observations. Dayiength is expressed as mean hours
during the growing season, and biomass as mean values during the
growing season. The growing season for Enteromorpha and Ulva was
between June and August; for Gracilaria between March and May; and
for microalgae between April and September.
Enteromorpha
and Ulva
DAYLENGTH
Gracilaria
Microalgae
12
12
(hours)
B I OMAS S
6.5
8.3
4.50
0.20
0.045
0.63
0.02
0.023
46.44
1.50
0.26
27.21
20.76
3.09
148.5
(g c ni2)
NET PRODUGT ION
(g C m2 h1)
RESPIRATION
(g C m2 h')
DAILY NET PRODUCTION
(g C m2 d1)
z GROWTH/DAya
% Growth/Day = 100 (in (Nt/No))/t; where N0 is the biomass at time zero,
Nt is the biomass at time t and t is in days.
-122-
a period of maximum growth and biomass for each functional group at the intensive study sites.
Net primary production and rates of respiration per hour
for macroalgae were taken from Table 24.
Microalgal biomass was estimated
from chlorophyll a concentrations at the intensive study sites during the
period of maximum growth.
Net primary production and rates of respiration per
hour were calculated from measurements of gross primary production and the
mean ratio given in Table 23.
Daily net primary production was estimated by
subtracting the respiration during the dark hours of the day from the net
primary production during the daylight hours.
Macroalgae were very productive (20 to 27% growth per day), especially
Enteromorpha and Ulva, which accounted for large seasonal inputs of organic
matter into Oregon estuaries.
Mean sediment-associated microalgal production
in the summer was much less than that of macroalgae (3.09% growth per day).
Admiraal and Peletier (1980) found similar growth rates in intact sedimentassociated diatom populations.
Macroalge are probably able to grow at a much
greater rate than sediment-associated microalgae because of their ability to
live on the sediment and in the water column and their greater rate of photosynthesis per unit chlorophyll a.
The macroalgae can absorb nutrients from
the sediment at low tide and maximize light capture by becoming suspended in
the water column during periods of inundation (Welsh, 1980).
Sediment-associ-
ated microalgae can also become suspended during inundation, but their growth
is probably limited by turbidity created by sediment particles associated with
the microalgae arid their mucus (Baillie and Welsh, 1980).
III.
Effects of Estuarine Infauna on Sediment-Associated Microalgae
This section presents the results of research conducted in collaboration
with Henry Lee, Marine Division of the Environmental Research Laboratory
-12 3-
(E.P.A.), Marine Science Center, Newport, Oregon.
National Research Council Fellowship with E.P.A.
Dr. Lee was supported by a
Also, we gratefully
acknowledge helpful suggestions by D. J. Specht, R. C. Swartz, and G. E.
Walsh, all of the Environmental Research Laboratory.
Importance of biotic factors in regulating sediment-associated microalgae
is poorly understood.
Many epifaunal and infaunal deposit-feeders ingest and
assimilate microalgae (Sanders et al., 1962; Levinton, 1980).
Experimental
manipulations of the estuarine gastropods Hydrobia spp. (Fenchel and Kofoed,
1976), Nassarius obsoletus (Say) (Pace et al., 1979), and Bembicium auratum
(Quoy and Gainard) (Branch and Branch, 1980), demonstrated that epifaunal
deposit-feeders can regulate microalgal biomass.
A freshwater epibeñthic
amphipod, Hyalella azteca (Sauggure), either stimulated or depressed microalgal production depending on amphipod density (Hargrave, 1970).
Experimental
studies of infaunal regulation of microalgae include the investigation by
White et al. (1980) who found that the sand dollar, Mellita quinquiesperforata
(Leske), had no significant effect on chlorophyll a concentrations in sediment
and the study by Coles (1979), who gave qualitative evidence for infaunal
regulation of microalgae.
In some preliminary experiments, we observed that defaunated sediment
developed a golden-brown "diatom" layer within a few days.
These observations
indicated that microalgal colonization was rapid and that infauna regulated
niicroalgal production.
To test these hypotheses
colonization of defaunated sediment in the field
we examined microalgal
and laboratory.
Here, we
present results of these experiments and discuss the role of infauna in controlling sediment-associated microalgae.
-124-
Study Site
Experiments were performed on an intertidal sand flat in Yaqunia Bay
adjacent to the Oregon State University Marine Science Center and in a laboratory at the Marine Science Center.
The field study site was 1.0 to 1.1 m
above MLLW and was exposed twice daily for an average exposure of 6 hours per
Maximum tidal amplitude in Yaqunia Bay is three meters.
day.
grain size was 2.64 phi, a fine sand.
Sediment mean
The microalgal community was composed
primarily of a diverse assemblage of pennate diatoms (Amspoker and Mclntire,
1978).
During the summer, the macroalgae Enteromorpha prolifera (Mull.) J.
Ag. and Ulva expansa (Setch.) S.&G. covered a large portion of the study
Rates of gross primary production by sediment-associated microalgae at
site.
this location ranged from 20 to 150 mg C m2 hr'.
Methods
1.
Experimental Design
The effect of infauna on microalgae was evaluated by comparing microalgal
biomass and production of an undisturbed sediment community with that of
defaunated sediment.
Defaunated sediment was sediment collected at the field
site, sieved through a 1-mm mesh screen, and frozen for approximately one
month.
In the field experiment, defaunated sediment was placed in cylinders
of fiberglass screening (1.5-mm mesh).
These cylinders had a surface area of
411.9 cm2, were 10 cm deep, and were completely embedded within the sediment.
Eight defaunated sediment cylinders and eight control plots (unmanipulated
sediment) were randomly assigned to 57 cm x 57 cm plots within a 285 cm x
228 cm block.
The experiment was initiated in June, 1980.
Macroalgae were
-125-
periodically removed from the study site.
Defaunated and control treatments
were sampled 1, 10, and 40 days after transplanting the defaunated sediment
At each sampling date, two defaunated cylinders and two con-
into the field.
trol plots were sampled.
Three cores (45.6 cm2, 4 cm deep) were taken within
each defaunated cylinder or control plot.
These cores were brought into the
laboratory and used to assess metabolic activity, chlorophyll a concentration,
and macrofaunal abundance.
In the laboratory experiment, cores (36.3 cm2, 4 cm deep) were either
taken in the field or filled with defaunated sediment and then maintained in
flowing seawater.
Microalgae growing on defaunated sediment came from an
initial inoculum of suspended microalgae originating from immersion of the
control sediment into the water bath and by surviving microalgae.
The sea-
water was sand-filtered, UV-treated, and maintained at 11.0 ± 1.0°C and a
salinity of 30 0/00.
Light was supplied by cool-white fluorescent and
incandescent sources at 150p E m2 sec
photosynthetically active radiation
with a 12-hour light and 12-hour dark photoperiod.
Light was measured with a
Licor® quantum meter and salinity with an A0 Goldberg® temperature-compensated
refractometer.
Metabolic activity, chlorophyll a concentration, and macro-
faunal abundance were determined 1, 10, and 40 days after initiation of the
experiment.
dates.
Three cores of both treatments were sampled on each of the three
The laboratory experiment was initiated in January, 1981.
To deter-
mine the effects of maintaining cores in the laboratory, metabolic activity,
chlorophyll a concentration, and animal abundance cere measured in three cores
taken from the field one day before termination of the experiment (i.e., day
39).
-126-
2.
Metabolic Activity
Gross primary production (GPP) and community oxygen uptake (OUPTK) were
measured in the laboratory using changes of oxygen in stirred, light and dark
chambers designed to hold intact cores of sediment (see page 44 of this
report).
In the field experiment, the three cores from a defaunated or
control plot were incubated in 6.0-1 plexiglas chambers (Fig. 8).
In the
laboratory experiment, a 300-mi plexiglas chamber was used for each intact
core (Figure 9).
The large chamber required 1 hour dark and
1 hour light
incubation for measurements of OUPTK and net community 02 production, respectively.
Incubations were performed at 13 to 14°C, a light intensity of 210 i.iE
m2 sec', and a salinity of 30 0/00.
hour for each condition.
The small chamber required one-half
Oxygen was measured polarographically using an
Orbisphere® salinity-compensated 02 system.
GPP was calculated by adding
OJJPTK to net community 02 production for an equivalent period of time.
lated rates of GPP in tug 02m2hr
were converted to mg Cm2hr' assundng
a photosynthetic quotient of 1.2 (i.e., mg C
in mg 02 m2 hr
3.
0.312 x tug 02), and OUPTK rates
were converted to mg C m2 hr
tient of 1.0 (i.e., mg C
Calcu-
assuming respiratory quo-
0.375 tug 02) (Westlake, 1965).
Chlorophyll a Analysis
The concentration of chlorophyll a in sediment samples was analyzed using
the method of Strickland and Parsons (1972).
After metabolic measurements, a
core (4.15 cm2, 3 cm deep) for chlorophyll a analysis was taken from each
larger core.
These smaller cores were frozen intact and the top cm was
sectioned off and then emersed in 90% acetone.
The concentration of chloro-
phyll a in the acetone extract was determined with a spectrophotometer, and
the Lorenzen equation was used to calculate tug chlorophyll a m2, corrected
-127-
for pheaopigments.
These values are not corrected for chlorophyllide, but are
suitable for comparing the effect of grazing on adjacent plots (Pace et al.,
1979; Whitney and Darley, 1979).
4.
Macrofaunal Abundance
After removing the subcores for the chlorophyll analysis, the remaining
sediment in each field core (40.05 cm2) or laboratory core (32.15 cm2) was
sieved through a 1.0 mm mesh screen.
The macrofaunal residue was preserved in
The macro-
buffered 10% seawater formalin which was dyed with rose bengal.
fauna was sorted later and identified under 12x magnification.
5.
Statistical Analysis
The significance of changes over time or differences between treatments
was tested using SPSS programs (Nie et al., 1975).
One-way analysis of
variance (ANOVA) was used to test for temporal changes with the defaunation
and control treatments analyzed separately.
Two-way ANOVA was used to test
The
for time, defaunatlon, and time by defaunation interaction effects.
small-sample t-test was used to test differences between treatments at
specific dates.
Statistical significance was defined at P < .05.
Infaunal
abundance was transformed using the expression y = log10 (x + 1), where x was
the numerical abundance.
formed.
Values for CHLR, GPP, and OUPTK were not trans-
tn the field experiment, values obtained for three cores from each
defaunated cylinder or control plot were averaged, resulting in two replications for each of the two treatments at each sampling date.
In the
laboratory experiment, each core was analyzed independently, resulting in
three replications for each treatment at each sampling date.
-128-
Results
1.
Field Defaunation Experiment
Chlorophyll a concentration in control sediment decreased significantly
during the 40-day experiment, whereas the concentration in defaunated sediment
increased significantly during this period (Fig. 24).
in a significant time by defaunation interaction.
This pattern resulted
Colonization of defaunated
sediment by microalgae was evident as golden-brown patches where defaunated
sediment had been transplanted.
Neither gross primary production (Fig. 25)
nor community oxygen uptake (Fig. 26) varied significantly over time or
between control and defaunated sediments.
Total infaunal abundance in control
sediment did not vary significantly over time, while animals in defaunated
sediment increased (P > .05) to control levels by day 40 (Fig. 27).
A tanaid,
Leptochelia dubia (Kr6yer) constituted > 63% of the individuals in defaunated
and control sediment.
Other abundant infaunal taxa were spinoids, capitel-
lids, amphipods, and the venerid bivalve Transennella tantilla (Gould).
Epi-
faunal species were not abundant at this site.
2.
Laboratory Defaunation Experiment
The chlorophyll a concentration in control sediment did not vary significantly over time (Fig. 28).
defaunation effects.
Two-way ANOVA indicated significant time and
By day 40, the chlorophyll a concentration was approx-
imately four times greater In defaunated sediment than In control sediment (P
< .05).
Gross primary production in control sediment did not vary signifi-
cantly over 40 days, but increased dramatically (P < .01) with time in defaunated sediment (Fig. 29).
Two-way ANOVA indicated significant time and
time by defaunation interactioneffects.
Both effects resulted from the rate
-129-
o
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JUNE FIELD EXPERIMENT
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DAY
JUNE FIELD EXPERIMENT
Concentratiofl of chlorophyll a and rate of gross primary
Figures 24 and 25.
production during the field defaunation experiment in June, 1980.
Values are means of two replicates.
-130-
00
30
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JUNE FIELD EXPERIMENT
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ADEFAUNATED TOTAL
60,000
(1)
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20,000
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I0
D AY
JUNE FIELD EXPERIMENT
Figures 26 and 27.
Rate of community oxygen uptake and abundance of animals
during the field defaunation experiment in June, 1980. Values
are means of two replicates.
-131-
250
tSE
'CONTROL
6 DEFAUNATED
200
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JAN. LAB EXPERIMENT
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£ DEFAUNATED
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a0
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50
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DAY
JAN. LAB. EXPERIMENT
Figures 28 and 29. Concentration of- chlorophyll a and rate of gross primary
production during the laboratory defaunation experiment in
January, 1981. Values are means of three replicates.
33('
-132-
of gross primary production in defaunated sediments starting from zero and
reaching relative high values by day 10.
By day 40, the rate was approx-
imately two times greater in defaunated sediment than in control sediment.
Oxygen uptake in the dark by control sediment did not vary significantly over
time, while values for this variable increased in defaunated sediment by day
10 and then decreased to values similarto the controls by day 40 (Fig. 30).
Two-way ANOVA indicated significant defaunation and time by defaunation interaction effects on oxygen uptake.
Total infaunal abundance in control sediment did not vary significantly
over time, whereas infaunal abundance in defaunated sediment was zero at days
1 and 10 and then increased to 311 tanaids per m2 by day 40 (Fig. 31).
Leptochelia dubia constituted more than 75% of the individuals in control
sediment.
Other abundant taxa in control sediment included spionids,
capitellids, and amphipods.
There were no significant differences in chlorophyll a concentration,
primary production, community oxygen uptake, or total infaunal abundance
between control cores maintained in the laboratory for 40 days and cores taken
in the field on day 39.
Interpretation of Defaunation Experiments
Microalgal colonization of defaunated sediment in the field was rapid as
indicated by the return of gross primary production (GPP) to control levels
within 10 days.
Chlorophyll a (CHLR) also returned to control level within
10 days though It is not possible to separate the amount of chlorophyllides
initially in the defaunated sediment from the import of viable microalgae.
Total infaunal density returned to control levels by day 40, as expected from
-133-
80
oJ
c,.J
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GO
E
Af
ri
010
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0
±SE
CONTROL
£ DEFAUN.ATED
20
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DAY
JAN, LAB. EXPERIMENT
S CONTROL TANAIDS
£ CONTROL TOTAL
DEFALJNATED TANAIDS
DEFAUNATED TOTAL
1E
0,
-J
z
I0
DAY
JAN. LAB EXPERIMENT
uptake and abundance of animals
Figures 30 and 31. Rate of community oxygen
defaunation
experiment in January, 1981.
during the laboratory
Values are means of three replicates.
-134--
previous experiments (H. Lee and J. Lee, unpublished).
Placement of de-
faunated sediment in the field simulated localized natural disturbances such
as those caused by epibenthic fishes and invertebrates or bioturbation (Lee
and Swartz, 1980).
The rapid recovery of both microalgal production and bio-
mass indicates that this microalgal assemblage was resilient to small-scale
disturbances.
This resilience was probably facilitated both by transport of
microalgae into disturbed areas (Tenore, 1977; Baillie and Welsh, 1980) and by
rapid growth of colonizing microalgae (Admiraal and Peletier, 1980).
Rapid
colonization on a localized scale does not imply that microalgae are resistant
to a generalized stress (e.g., pollution) or overlapping localized disturbances such as occurs in a Callianassa bed.
We hypothesized that removal of infauna would stimulate microalgal
production and biomass.
experiment.
This result was not readily observed in the field
The possible import of microalgae into defaunated sediment during
initial stages of colonization and export during later stages of colonization
and initial presence of chlorophyllides in defaunated sediment would tend to
minimize differences in chlorophyll a concentration and primary production
between control and defaunated sites.
Recolonization by infauna could also
minimize differences between treatments.
To better evaluate influences of the
infauna on microalgal biomass and metabolism, a laboratory experiment was
performed which eliminated the confounding effects of import-export of microalgae and infaunal colonization.
Similarity of levels of chlorophyll, gross
primary production, community oxygen uptake, and infaunal abundance between
control cores held in the laboratory for 40 days and the natural field community suggested that maintenance of cores did not affect community structure or
-135-
function.
Therefore, the laboratory experiment was considered an appropriate
method to determine effects of infauna on sediment-associated microalgae.
In the laboratory, removal of infauna caused a significant increase in
microalgal biomass and production.
The relatively high concentration of
chlorophyll a in defaunated sediment by day 1 was not functional as indicated
by the low rate of primary production.
Growth of microalgae in the defaunated
sediment was indicated by an increase in primary production by day 10,
By day 40,
although the chlorophyll concentration remained constant.
chlorophyll concentration and the rate of gross primary production in
defaunated sediment were significantly higher than in control sediment.
These
results suggested that natural densities of infauna can control both
microalgal biomass and production, as has been found in several other studies
of estuarine epifaunal gastropods (Fenchel and Kofoed, 1976; Pace et al.,
1979; Branch and Branch, 1980).
Natural infaunal density at the study site
exceeded the level at which microalgal and microbial populations are
stimulated by consumption of senescent cells or nutrient additions (Margrave,
1970, 1976; Cooper, 1973; Porter, 1976; Pace et al., 1979).
Grazing is the most likely mechanism by which infauna controlled microalgal biomass and production.
The most abundant species at the study site,
Leptochelia dubia, contained both broken and whole diatom frustules in its
gut, indicating herbivory.
The same food resource was found for another
tanaid, Leptochelia rapax (Harger) (Kneib et al., 1980).
Burial of cells by
sediment turnover is another mechanism by which infauria can limit microalgae.
However, Leptochelia does not appear to turn over large quantities of
sediment (Myers, 1977), and large sediment reworkers such as Callianassa and
Upogebia were not abundant at our study site.
The process of defaunating
-136-
sediment may have increased nutrient concentrations which in turn could have
stimulated microalgal growth.
However, field and laboratory nurient-addition
experiments at the study site indicated that sediment-associated microalgae
were not nutrient-limited (Cardon, 1981).
Patterns of oxygen uptake were difficult to interpret.
In the field,
oxygen uptake in defaunated sediment recovered to control values between days
10 and 40.
In the laboratory, oxygen uptake of defaunated sediment was
initially identical to control sediment, increased to greater than control
levels between days 1 and 10, and then decreased to control values between
days 10 and 40.
Causes for the different patterns in the field and laboratory
experiments were not apparent.
The low macrofaunal density (0 to 311 m2)
and diversity (0 to 1 species) in the defaunated sediment in the laboratory
normally would constitute strong evidence for a highly degraded benthic
community.
Yet oxygen uptake at day 40 was the same for control and
defaunated sediment.
This similarity of community metabolism between these
radically different benthic communities indicates that there is no simple
relationship between oxygen uptake and community structure.
Also, the effect
of heterotrophic microorganisms on these experiments is unknown.
We have presented experimental evidence for a controlling effect of
infaunal animals on estuarine sediment-associated microalgae.
As suggested
by Pace et al. (1979), herbivory is one of the factors regulating microalgal
biomass and production although its relative importance, compared to other
factors, is unknown.
Differences in infaunal abundance and activity may be
one of the factors influencing both spatial and temporal patterns of
microalgae (Cadêe and Hegeman, 1974; Coles, 1979).
The influence of animals
on plant communities is a widespread phenomenon and should not be ignored when
assessing controlling factors of plant growth (Brook, 1955, 1975).
-137-
IV.
The Diatom Flora of Netarts Bay
Figure 5 indicated that microalgae and several macroalgae are important
groups of autotrophs in Oregon estuaries.
Among the microalgae, the diatoms
are by far the most abundant and diverse group, with representative taxa found
in the water column, in the sediment, and growing as epiphytes on Zostera
marina and macroalgae.
In this section the taxonomic structure of the diatom
assemblages of Netarts Bay is examined and related to selected environmental
variables.
Such information relates to patterns of primary production and to
patterns of water circulation in the estuary.
Also, the species composition
of estuarine diatom assemblages can be used as an indicator of certain aspects
of the chemical and physical environment.
Sampling
The distribution and relative abundances of diatom taxa were examined in
planktonic, epiphytic and sediment collections during a one year period from
February 1980 to March 1981.
Samples were collected once each month on dates
that corresponded to favorable tide and weather conditions.
Sampling
stations were established at sites A, B, and C in Netarts Bay (Fig. 7), which
represented different sediment types (i.e., sand, fine sand, and silt).
Samples of the sediment-associated diatom flora were obtained from four tidal
heights along an intertidal transect at each site.
These sampling stations
were the same stations that were established to study microalgal primary
production (see page 41).
near site B.
Epiphytic diatoms were collected from a study area
In this case, samples were obtained from three locations, 1.1 m,
1.2 m, and 1.4 m above MLLW, along an intertidal gradient across a
-138-
large Zostera bed.
A detailed description of this Zostera bed is reported in
a later section and in Figures 32-34.
planktonic diatoms were obtained from:
On each sampling date, collections of
(1) bay water at low tide near site B;
(2) ocean water at high tide near the mouth of the bay; and (3) from water
near Site B at high tide.
Methods
Samples of planktonic diatoms were collected by pouring 10 1 of water
through a 10 1.im mesh plankton net.
Planktonic diatoms were cleared of
pigments in ethanol, and sea salt and other dissolved solids were removed from
the samples by successive washings in distilled water.
After washing, a sub-
sample of the diatom suspension was transferred to a microscope coverslip and
allowed to air dry.
Coversllps with the dry diatom deposits were mounted on
microscope slides using Cumarone resin (Holmes etal., 1981).
One shoot of Zostera marina and its associated epiphytic diatoms was
collected from each of the three intertidal sampling stations near site B on
each sampling date.
These samples were placed in screw-top bottles and were
transported to the laboratory for processing.
Benthic sediment cores were obtained at the intertidal stations at site
A, B, and C on each sampling date.
These samples were taken by pushing a
2.3 cm diameter plastic pipe into the sediment and extracting the upper 2-3 cm
of sediment and its associated microflora.
The cores were capped, transported
to the laboratory in a vertical position, and frozen until the cleaning
procedure was initiated.
the cleaning procedure.
Diatoms in the top cm of each core were isolated by
-139-
Organic materials in the epiphytic and sediment samples were removed by
nitric acid digestion in a Kjeldahl apparatus.
Large sediment particles were
separated from the diatoms by rapid decanting, and the clean diatom frustules
were allowed to settle in beakers for at least 4 hr.
After several washings
with distilled water, the isolated frustules were mounted on microscope slides
following the procedure described above for the planktonic taxa.
Epiphytic and sediment-associated diatoms were identified and counted
with a Zeiss research microscope at 1200x magnification using brightfield
Approximately 500 valves were identified for each sample, a
illumination.
sample size that was compatible with the statistical methods used to report
the results (Mclntire and Overton, 1971).
Epiphytic samples from all
12 months were counted for a total of 36 samples.
Of the 116 benthic samples
collected, samples from every other month were counted for a total of
64 samples.
Results of the examination of plankton samples are reported as
species lists.
Since the diatom collections were obtained concurrently with the sampling
programs designed to study microalgal and Zostera primary production and biomass, measurements of physical and biological variables obtained during these
investigations also were used to interpret distributional patterns in the
diatom flora.
Variables of particular interest included intertidal height,
chlorophyll a and organic matter concentrations in the top cm of sediment, the
ratio of chlorophyll a concentration in the top cm of sediment to that at a
depth of 4-5 cm, day length, water temperature, mean sediment particle size,
the sediment sorting coefficient, and the sediment skewness coefficient.
Methods associated with the collection of these data are described on pages
44-49 of this report.
-140-
Data Analysis
The analysis of distributional patterns in the diatom flora of Netarts
Bay involved:
1.
A principal component analysis of physical and biological
environmental data;
2.
Calculation of niche breadth values (Mclntire and Overton, 1971) for
selected epiphytic and sediment-associated taxa;
3.
The regression of the relative abundance of selected epiphytic and
sediment-associated taxa against environmental variables and principal
components of environmental variables;
4.
Comparisons of assemblages pooled as epiphytic, sand taxa, fine sand
taxa, and silt taxa by SIMI, a measure of similarity (Mclntire and
Moore, 1977);
5.
Ordination of samples and taxa by reciprocal averaging(Hill, 1973);
and
6.
Correlation of ordination scores for sites with selected environmental
variables.
All data analyses were performed on a Control Data Corporation CYBER
170/720 computer system at the Oregon State University Computer Center using
the AIDNX, ORDIFLEX, CORRELX, and PARTL computer programs, and SIPS, a
statistical interactive programming system.
-14 1-
Results
1.
Structure of Environmental Data.
Environmental variables were organized in two data sets, one with
environmental variables corresponding to the epiphyte samples and another with
variables corresponding to the sediment samples.
Variables related to the
epiphyte samples included intertidal height, daylength, and water temperature.
The Interrelationships among these variables were investigated by correlation
analysis.
Tidal height was virtually uncorrelated with daylength (r = 0.00)
and with water temperature (r = 0.08), while the covariance between daylength
and water temperature, variables related to season, was high (r
0.82).
The
environmental data were matched with 18 samples of epiphytic diatoms for
alternate months.
Environmental data corresponding to sediment samples consisted of nine
variables, namely intertidal height (TIDE), surface chlorophyll a (CHLA),
surface organic matter (OM), the chlorophyll ratio (RATIO), daylength (DAYL),
water temperature (TEMP), mean particle size (PHI), and the sorting and
skewness coefficients (SORT and SKEW).
Covariances among the sediment
properties PHI, SORT and OM were relatively high, and correlation coefficients
for these variables were 0.67 (PHI-OM), 0.78 (SORT-OM), and 0.83 (PHI-SORT).
Moreover, daylength and water temperature were closely correlated with each
other (r = 0.76).
The variables tidal height, surface chlorophyll, the
chlorophyll ratio, and the skewness coefficient were not highly correlated
with each other and with other variables (correlation coefficients below
0.40).
The environmental data were matched with 64 samples of sediment-
associated diatoms from alternate months.
-142-
The relatively large environmental data set associated with the benthic
diatom samples was summarized by the concentration of variance into three
The interpretation of the principal components was
prinicipal components.
achieved by the examination of factor loadings, i.e., the correlations between
the components of interest and the original variables (Table 26).
Relatively high correlations (r > 0.8) between the first principal
component and OM, PHI and SORT indicated that this axis was an expression of
sediment properties.
The second axis was highly correlated (r > 0.9) with
daylength (DAYL) and with water temperature (TEMP), and was interpreted as a
seasonal component.
The third axis was highly correlated (r = 0.81) with
intertidal height (TIDE).
The low communalities for surface chlorophyll (CHLA), the chlorophyll
ratio (RATIO) and the skesmess coefficient (SKEW) indicated that these
measures were not expressed appreciably by the first three components.
Eigenvalues indicated that the first three principal components accounted for
66% of the total variation in the environmental data, and 33% was expressed by
the first axis alone.
2.
The Diatom Flora
Planktonic, epiphytic, and sediment-associated diatom samples contained a
total of 340 taxa (species and varieties of species) from 73 genera.
Of these
taxa, 50 were planktonic and 294 were either epiphytic, associated with
sediment, or both.
Only five taxa, namely Thalassiosira 1, Thalassiosira
decipiens, Thalassiosira pacifica, Thalassionema nitzschioides and Skeletonema
costaturn, occurred among planktonic, sediment and epiphytic assemblages.
-143-
Table 26.
Factor loadings for the first three principal components generated
from the environmental variables associated with sediment samples.
Variables are intertidal height (TIDE), chlorophyll a concentration (CHLA), sediment organic matter (OM), chlorophyll ratio
(RATIO), daylength (DAYL), water temperature (TEMP), mean sediment
particle size (PHI), sorting coefficient (SORT), and the skewness
coefficient (SKEW). Loadings with an absolute value greater than
0.8 are underlined for emphasis.
PCA1
PCA2
PCA3
r2
r3
Communality
TIDE
-0.16
-0.18
0.81
0.72
CHLA
-0.50
-0.12
0.44
0.45
OM
-0.88
-0.10
0.07
0.78
0.57
-0.07
0.40
0.48
DAYL
-0.03
0.93
0.13
0.88
TEMP
-0.00
0.93
0.13
0.88
PHI
-0.85
-0.03
-0.09
0.73
SORT
-0.91
-0.11
0.11
0.85
SKEW
-0.21
-0.03
0.38
0.15
2.94
1.80
1.12
RATIO
Elgenvalues
% of variance
extracted
33%
20%
13%
-144-
Approximately 53,850 diatom valves were identified and counted in
64 benthic samples and 36 epiphytic samples.
Epiphyte samples collected
monthly from three intertidal stations resulted in a count of 19,463 valves
and the identification of 123 taxa.
Sediment samples from every other month
along four intertidal stations resulted in the identification of 34,851 valves
that represented 282 taxa.
The overlap between benthic and epiphytic
assemblages was 111 taxa, or 38% of the total for the two assemblages.
As is usually the case, most of the species within the assemblages were
rare.
Taxa represented by five or fewer valves accounted for 38% of the total
number of taxa identified.
Such rare taxa contribute relatively little
information to the analysis of distributional patterns, as their occurrence in
a sample may represent allochthonous inputs, not a reflection of local
environment.
Consequently, specific taxa of interest were chosen for the
statistical analysis on the basis of their abundance, and the rarer taxa were
eliminated.
The 72 taxa chosen for ordination accounted for 95% of all
epiphyte valves counted and 91% of all valves counted for the sediment
samples.
The 36 sediment-associated taxa chosen for the regression analysis
accounted for 79% of all valves counted for the sediment samples.
The 22
epiphytic taxa chosen for a regression analysis with environmental variables
accounted for 94% of all epiphytic valves counted.
In general, the taxa found in plankton samples were benthic or epiphytic
taxa that were dislodged and suspended in the water column by tidal currents
and turbulence.
Common benthic species in these samples included Paralia
sulcata, Anaulus balticus, Navicula digitoradiata, Navicula cancellata,
Nitzschia socialis and Nelosira moniliformis.
Epiphytic taxa found as
-145-
tychoplankton included Cocconeis scutellum, Cocconeis scutellum v. parva,
Synedra fasciculata and Navicula directa.
Euplanktonic species were abundant
only in samples from February, March and August of 1980.
In these samples,
the species were typical of those found in the neritic plankton along the
Oregon Coast, and the presence of marine plankton in Netarts Bays apparently
was due to seawater transport into the bay by tidal fluxes.
Samples of plankton from the three months that had marine neritic floras
are compared in Table 27.
Although samples from February and March shared
fewer taxa (26%) than the February and August samples (38%), the February and
March samples were dominated by the same species, namely Nitzschia seriata, N.
pungens, Chaetoceros compressus, Skeletonema costatum, Thalassiosira
decipiens, T. 1, and Rhizosolenia setigera.
August plankton samples were
dominated by several species of Chaetoceros, contained different species of
Nitzschia and Thalassiosira than February and March samples, and lacked
species of Rhizosolenia.
Dominant species in the August samples included
Chaetoceros coinpressus, C. constrictus, C. socialis, Nitzschia pacifica,
Eucampia zodiacus, Thalassiosira nordenskioeldii, and T. pacifica.
The relative abundances and niche breadth values for 72 common benthic
and epiphytic taxa are presented in Table 28.
The most abundant epiphytes
were Navicula salinicola, Navicula tripunctata v. schizonemoides, Navicula
frustulum v. subsalina, and Synedra fasciculata; while the most abundant
sediment-associated taxa were Achnanthes hauckiana, and Opephora pacifica.
In
this case, niche breadth values may range from 1.0 if a species was present in
only one sample, to 82 if equally abundant in all 82 samples.
Although
Paralia sulcata was not very abundant in the samples, it had a relatively high
-146-
Table 27.
A list of planktonic species found in Netarts Bay during months in
1980 when the flora was dominated by marine neritic taxa.
Plus
signs (+) indicate that a taxon was present.
February
March
Actinocyclus octonarius
+
Actinocyclus splendens
+
Asterionella japonica
August
+
Bacteriastrum delicatulum
Bacteriastrum hyalinum
Biddulphia longicuris
+
Chaetoceros armatum
+
Chaetoceros compressus
+
+
Chaetoceros constrictus
+
+
+
Chaetoceros curvisetus
Chaetoceros decipiens
+
Chaetoceros didymus
+
Chaetoceros lacinosus
+
Chaetoceros lorenzianus
+
Chaetoceros radicans
+
Chaetoceros socialis
+
Chaeto ceros vanheurcki
+
Corethron hystrix
Coscinodiscus curvatulus
Coscinodiscus eccentricus
Coscinodiscus radi atus
+
+
+
-147-
Table 27 (continued)
February
March
August
Coscinodiscus sublineatus
±
Hemlaulus hauckii
+
+
Lithodesmium undulatus
+
Leptocylindrus danicus
-f
Lauderia borialis
+
+
Eucampia zodiacus
+
Ditylum brightwellii
Navicula complanatula
Navicula planamembranacea
+
Nitzschia delicatissima
+
Nitzschia pacifica
+
Nitzschia pungens
Nitzschia seriata
+
+
Pleurosigma normanii
+
Rhizosolenia alata
+
Rhizosolenia hebatata v.
semispinosa
+
Schroederella delicatula
+
+
Skeletonenia costatum
+
Stephanopyxis nipponica
+
Stephanopyxis palmeriana
+
Thalassionema nitzschioides
+
±
+
+
Rhizoselenia setigera
Thalassiosira 1
+
Thalassiosira aestivalis
+
Thalassiosira decipiens
+
+
Thalassiosira nordenskioeldii
+
+
Thalassiosira pacifica
+
Thalassiosira rotula
+
Thalasslosira longissima
+
-148-
Table 28.
A list of 72 selected taxa, their total relative abundance (NT),
and their relative abundance in epiphyte (NE) and benthic (NB)
samples.
Also listed is the niche breadth values (B) for each
taxon in relation to 82 epiphyte and benthic samples.
NT
NB
NE
Achnanthes 1
440
0
440
31.44
Achnanthes 11 B
918
0
918
20.26
3244
9
3235
30.86
Achnanthes latestriata
172
0
172
19.63
Achnanthes lemmermanni
621
2
619
36.51
72
0
72
13.84
Amphora coffeiformis
441
4
437
43.20
Amphora exigua
349
2
347
19.87
Amphora laevis v. perminuta
155
0
155
14.99
Amphora libyca
148
0
148
22.65
Amphora micrometra
499
0
499
19.28
79
0
79
9.03
1695
7
1688
41.31
Amphora tenerrima
678
104
574
38.48
Anorthoneis eurystoma
118
1
117
8.32
Bacillaria paradoxa
192
171
21
7.44
Berkeleya rutilans
473
373
100
9.32
Cocconeis 11 A
1649
2
1647
40.87
Cocconeis 11 C
336
2
334
32.89
Cocconeis J
991
11
980
28.39
Cocconeis costata
460
390
70
14.40
1365
38
1327
42.48
Cocconeis scutellum
798
585
213
19.92
Cocconeis scutellum v. parva
529
481
48
9.91
1117
0
1117
21.64
Achnanthes hauckiana
Amphora 35
Amphora proteus
Amphora sabyii
Cocconeis placentula v.
euglypta
Cymbellonitzschia
hossamedinii
-149-
Table 28 (continued)
NT
NB
NE
96
0
96
10.04
Fragilaria striatula v.
californica
212
2
210
2.54
Gomphonema oceanicum
458
413
45
9.55
Gyrosigina prolongum
42
1
41
3.97
Hantzschia 1
38
0
38
6.44
Hantzschia marina
62
0
62
6.58
278
37
241
6.18
Melosira nummuloides
82
17
65
4.54
Navicula 3
71
2
69
3.36
Navicula 16
206
0
206
3.14
Navicula 109
460
16
444
24.27
Navicula 150
201
129
72
14.93
Navicula 199
1100
0
1100
17.30
Navicula ammophila v. minuta
144
0
144
16.84
Navicula directa
542
535
7
6.90
Navicula diserta
340
0
340
41.91
Navicula diversistriata
332
2
330
15.86
Navicula forcipata
120
0
120
15.01
Navicula gottlandica
162
0
162
9.06
Navicula gregaria
857
4
853
32.34
76
0
76
5.47
214
1
213
20.18
48
0
48
9.66
3665
1760
1905
41.12
69
0
69
2.49
1229
930
229
24.86
Nitzschia 2
82
0
82
16.51
Nitzschia 5
100
62
38
19.64
Nitzschia 47
117
0
117
3.18
Fragilaria pinnata
Melosira inoniliformis
Navicula grostchopfi
Navicula patrickae
Navicula sauna
Navicula salinicola
Navicula tripunctata
Navicula tripunctata v.
schizonemoides
-150-
Table 28 (continued)
NB
NT
NE
223
202
21
3.72
78
78
0
3.08
314
207
107
29.97
41
0
41
12.92
Nitzschia frustulum v.
subsalina
2456
1060
1396
37.13
Nitzschia fundi
1524
472
1052
42.75
274
191
83
13.86
21
0
21
16.23
232
191
41
8.54
3503
6
3497
54.23
Opephora perminuta
262
1
261
15.80
Opephora schultzi
237
3
234
34.15
Paralia sulcata
565
18
546
45.06
Rhoicosphenia curvata
56
49
7
11.60
Rhopalodia musculus
65
3
62
8.51
Synedra fasciculata
851
803
48
15.14
1037
119
918
42.65
246
2
244
11.62
Nitzschia 171
Nitzschla brevirostris
Nitzschia dissipata v. media
Nitzschia frustulum
Nitzschia pseudohybrida
Nitzschia punctate
Nitzschia rostellata
Opephora pacifica
Thalassiosira 1
Trachysphenia australis
-151-
niche breadth value because of its presence in numerous sediment and epiphyte
samples.
In contrast, Opephora pacifica derived its large niche breadth value
from its high relative abundance in numerous sediment samples.
Several species had low niche breadth values, indicating a restricted
distribution, and yet made a substantial contribution to the samples in which
they were found.
Fragilaria striatula v. californica constituted approx-
imately one-fifth of the total valves in two samples from the SAND site (1.0
above MLLW) in August and October.
absent or rare.
In all other samples, this taxon was
Navicula 3 was abundant only in February in samples from the
SAND Site at 1.5 m and 2.0 m above MLLW.
Although Navicula 16 was found only
in sand samples and was usually rare, this diatom represented about two-fifths
of all the valves identified from 2.0 m above MLLW in April.
Nitzschia 171
and Nitzschiabrevirostris were epiphytic taxa with restricted distributions.
Nitzschia brevirostris was abundant only in the three epiphyte
samples from October, and Nitzschia 171 was abundant in the September epiphyte
samples where it was found in the colonial muselage of Bacillaria paradoxa.
3.
Autecology of Selected Taxa.
The relationship between the relative abundance of 22 selected epiphytic
taxa and three environmental variables are presented in Table 29.
The
coefficient of determination (R2) for the multiple regression of each taxon
against all three variables ranged from 0.02 for Cocconeis scutellum to 0.81
for Nitzsehia fundi; nine of the 22 taxa had R2 values 0.50 or greater.
Most
of the covariance between species abundance and the environmental variables
was associated with seasonal fluctations in the flora, as the relative
abundance of nine taxa were correlated (r > 0.50) with daylength and water
-152-
Table 29.
The relationship between 22 selected epiphyte taxa and three
environmental variables:
intertidal height (TIDE), daylength
(DAYL), and water temperature (TEMP). Correlation coefficients are
given for each taxon, as well as the coefficient of determination
(R2) for the multiple regression of the abundance of each taxon
against the three variables.
TIDE
DAYL
TEMP
R2
Amphora tenerrima
0.19
0.48
0.37
0.27
Bacillaria paradoxa
0.02
0.11
-0.14
0.17
Berkeleya rutilans
0.11
0.53
0.42
0.30
Cocconeis costata
0.08
0.34
0.12
0.20
-0.08
-0.01
0.05
0.02
0.30
0.70
0.58
0.58
-0.16
-0.07
-0.43
0.44
0.07
0.50
0.28
0.30
-0.01
-0.46
-0.39
0.22
0.24
-0.38
0.03
0.52
-0.23
-0.74
-0.57
0.61
Nitzschia 5
0.03
-0.22
-0.49
0.32
Nitzschia 171
0.05
0.12
-0.03
0.07
Nitzschia brevirostris
0.05
-0.24
-0.58
0.53
Nitzschia dissipata v.
media
-0.09
-0.14
-0.57
0.66
Nitzschia frustulum v.
subsalina
0.18
0.81
0.68
0.69
Nltzschia fundi
0.09
0.89
0.81
0.81
Nitzschia pseudohybrida
0.02
-0.50
-0.70
0.50
Nitzschia rostellata
-0.08
-0.10
-0.37
0.27
Rhoicosphenia curvata
-0.21
0.23
0.08
0.12
Synedra fasciculata
-0.05
0.06
-0.37
0.55
0.13
0.10
0.05
0.03
Cocconeis scutellum
Cocconeis scutellum v.
parva
Gomphonema oceanicum
Navicula 150
Navicula directa
Navicula salinicola
Navicula tripunctata v.
schizonemoides
Thalassiosira 1
-15 3-
temperature (Table 29).
Navicula tripunctata v. schizonemiodes, Nitzschia
frustulum v. subsalina, and Nitzschia fundi were abundant throughout the year,
but had a distinct maximum occurrence during winter, spring, or summer,
respectively.
Cocconeis scutellum v. parva and Berkeleya rutilans were absent
or rare in the summer or fall, but were common during winter and spring.
Several species of Nitzschia were common in the October samples, namely N.
brevirostris, N. dissipata v. media, N. pseudohybrida, N. rostellata and
Nitzschia 5.
Nitzschia 171 was present only in September samples, and
therefore had a distinct seasonality in spite of its low correlations with
daylength and water temperature.
Correlations of relative abundances of the
22 epiphytic taxa with tidal, height were relatively weak, only Cocconeis
scutellum v. parva exhibited a weak relationship with intertidal position (r
0.30).
Relationships between the distribution of 36 sediment-associated taxa and
the environmental data are summarized in Table 30.
Twenty-two of these taxa
were at least weakly associated (r > 0.38) with the first principal component
of the environmental data matrix, and 13 taxa have correlation coefficients of
0.50 or greater.
This component expressed sediment properties, especially OM,
PHI, and SORT (Table 26).
Negative correlation coefficients for Achnanthes 1,
Achnanthes 11B, Amphora micrometra, Navicula gottlandica, and Opephora
schultzi indicated that these taxa were associated with sediments that were
composed of finer particles, were poorly sorted, and had a high concentration
of organic matter.
The high positive correlations for Achnanthes latestriata
Amphora proteus, Anorthoneis eurystoma, Cocconeis J, Cymbellonitzschia
hossamedinii, Navicula ammophila v. minuta, Navicula 16, and Navicula
Table 30.
R
= r
+ r
+ r
and R2 is the
2
0.66
0.61
0.46
0.48
0.34
0.22
0.58
0.55
0.44
0.39
0.36
0.32
0.23
0.19
0.55
0.44
0.22
0.14
0.40
0.17
0.52
-0.07
0.40
-0.18
0.40
-0.07
-0.05
-0.18
-0.00
0.28
-0.42
-0.17
0.25
-0.36
-0.19
-0.03
-0.24
-0.21
0.12
-0.26
0.28
-0.01
-0.07
-0.11
0.00
0.18
-0.07
-0.02
0.10
-0.47
0.55
0.44
0.49
0.39
0.39
-0.74
0.59
-0.20
0.29
0.58
-0.20
0.68
Ach nanthes 11 B
Achnanthes haucklana
Achnanthes latestriat a
Achnanthes lemmermanni
Amphora exigua
Amphora laevis V. perminuta
Amphora libyca
Amphora proteus
Amphora sabyil
Amphora tenerrima
Anorthoneis eurystoma
Cocconeis J
Cocconeis 11 A
Amphora microuietra
0.67
0.24
0.79
0.64
0.29
0.33
0.43
0.48
0.46
0.02
0.06
1
-0.67
Achnanthes
r3
r2
r1
R
2
Rf
PC3
PC2
PCI
against all environmental variables.
coefficient of determination for the multiple regression of species abundance
derived from the components analysis, where R
regression of the species variables against the first three principal factors
r3) are given for each component.
components of the environmental data matrix.
Correlation coefficients (r1, r2 and
is the coefficient of determination for the
The relationship between 36 sediment-associated taxa and the first three principal
-154-
0.00
0.04
-0.32
-0.12
0.20
0.44
0.04
0.32
0.17
-0.05
0.16
0.03
-0.32
-0.13
-0.02
0.20
-0.00
-0.29
-0.32
0.05
0.49
-0.16
0.34
0.18
0.58
0.57
-0.52
0.01
-0.44
-0.44
-0.24
-0.39
-0.41
-0.34
-0.09
-0.62
Navicula 109
ott1andica
Trachysphenia australis
Thalassiosira I
Opephora schultzi
Opephora perininuta
Opephora pacifica
Nitzschia fundi
subsaitna
Nitzschia 47
'Titzschia frustulum v.
Navicula saliuicola
Navicula groschopfi
Navicula gregaria
Navicula
Navicuia diversistriata
Navicula amrnophila v. minuta
Navicula 199
0.13
0.32
-0.45
0.14
0.24
-0.00
-0.32
-0.27
-0.26
0.59
-0.22
Navicula 16
0.02
0.12
0.20
Navlcula 3
-0.05
-0.05
-0.20
-0.01
hossamedinli
Melos ira moniliformis
Cyinbellonitzschf a
0.26
0.53
r3
r2
-0.46
-0.10
-0.10
PC3
PC2
0.13
0.17
0.17
PCi
0.28
Cocconeis placentula v.
euglypta
Table 30 (continued)
0.23
0.44
0.15
0.15
0.48
0.28
0.12
0.29
0.04
0.04
0.12
0.32
0.46
0.13
0.34
0.45
0.28
0.08
0.39
0.27
0.28
R
0.31
0.54
0.25
0.30
0.61
0.48
0.25
0.47
0.12
0.12
0.22
0.41
0.55
0.32
0.41
0.56
0.43
0.26
0.51
0.34
0.32
-156-
diversistriata indicated that these taxa were associated with sandy, wellsorted sediments with low organic content.
did not expose obvious patterns in the data.
In some cases, the linear model
For example, Amphora exigua,
Amphora laevis v. perminuta and Amphora libyca had from 77% to 82% of their
total relative abundance in sand samples and yet exhibited weak correlations
with the first principal factor (r = 0.39 to 0.49).
Melosira moniliformis was
an extreme case, with 63% of its valves in sand samples and 96% of its valves
in sand and fine sand samples together, and a correlation with the sediment
factor of only -0.05.
The second principal component is correlated with daylength and
temperature, variables that express seasonal changes.
En general, species
correlations with this axis were weak except for Navicula 109 and Nitzschia
fundi.
These taxa were most common in the summer.
The third principal component is an expression of intertidal height.
Species correlations with this component also were weak, with no correlation
coefficient greater than 0.50 and most values less than 0.30.
Achnanthes
hauckiana, Achnanthes lemmermanni, and Navicula groschopfi had a positive
correlation with this component Cr values between 0.40 and 0.44); while
Amphora sabyii, Cocconeis placentula v. euglypta, Cymbellonitzschia
hossamedinii and Thalassiosira 1 had negative correlations with this component
(r values between -0.39 and -0.46).
The former group of species was
associated with high intertidal stations, whereas the latter group was
associated with the lower stations.
Taxa mentioned above that were associated with factors 1, 2, or 3 have R2
values ranging from 0.22 to 0.55 for the multiple regression of relative
abundance against the first three principal components of the environmental
-157-
The total
data.
for the multiple regression of each of these taxa against
all nine environmental variables ranged from 0.34 to 0.79.
4.
CommunIty Patterns
Both Jaccard and SIMI indices of similarity were used to compare the
species composition of epiphytic and benthic assemblages (Table 31).
The Jaccard index indicated that the epiphyte samples had from 32% to 35%
of their taxa in common with samples from the SAND, FINE SAND, or SILT
sites.
Samples from the three sediment types shared a greater percentage of
taxa among themselves, in this case from 52% to 59%.
In contrast to the
Jaccard index, SIMI reflects the relative abundances of species as well as
their joint occurrences in samples; a high value usually indicates that the
assemblages have the same dominant taxa.
SIMI values ranged from 0.18 to 0.84
and emphasized the differences between the epiphyte samples and the sediment
samples (SIMI = 0.18 to 0.40) as well as the similarities among sediment
samples (SIMI = 0.56 to 0.84).
Epiphytic samples were more similar to samples
from the SILT site than to samples from the SAND or FINE SAND sites, while
assemblages from sand were more similar to those from fine sand than from
silt.
Species and samples were ordered along ordination axes by the method of
Reciprocal Averaging (RA).
The data for this analysis consisted of species
abundances counts for a total of 82 samples, of which 18 were epiphytic
collections and 64 were from the sediment.
The first ordination axis
separated the epiphytic samples from the sediment samples; while the second
axis represented a continuum relative to sediment type, with samples from the
SAND site at the top right of the graph, those from the FINE SAND site at the
center right, and assemblages from the silt site at the bottom right (Fig.
32).
-158-
Table 31.
A comparison of the similarity of pooled epiphytic and benthic
samples using SIMI and Jaccard indices.
SIMI compares the presence
and relative abundance of species among samples and is found in the
lower left half of this table.
The Jaccard index uses only
presence-absence data and forms the upper right half of the table.
The pooled samples are epiphytes (EP) and the assemblages from the
Sand (SA), Fine Sand (FS) and Silt (SI) sites.
SA
EP
0.35
SA
0.18
FS
0.29
0.62
St
0.40
0.56
0.32
0.32
0.54
0.52
0.59
0.84
-159-
The correspondence of site and species ordinations can be examined by a
comparison of Figure 32 with Figure 33.
left side of Figure 33 (group 1).
Epiphytic species are found on the
These species are Nitzschia brevirostris,
Rhoicosphenia curvata, Navicula directa, Gomphonema oceanicum, Synedra
fasciculata, Bacillaria paradoxa, Cocconeis costata, Cocconeis scutellum V.
parva, Nitzschia 5, Navicula tripunctata v. schizonemoides, Nitzschia
dissipata v. media, Nitzschia psuedohybrida, Nitzschia rostellata, Nitzschia
171, Navicula 150 and Cocconeis scutellum.
Sediment-associated species are
found on the right side of the diagram, with species from sand on the top,
species from fine sand in the center, and species from silt on the bottom.
Taxa that were abundant in all sediment types (group 8) are in the center near
the right margin of the figure.
These taxa are found mixed with species that
had greater fidelity to specific substrates (mainly groups 5 and 6).
Species
that were found in benthic as well as epiphytic samples are in the center of
the figure (group 9).
These taxa are Navicula salinicola, Navicula 109,
Navicula 3, Nitzschia frustulum v. subsalina, Nitzschia fundi, Melosira
nummuloides, Melosira moniliformis, Thalassiosira 1, Berkeleya rutilans, and
Amphora tenerrima.
A group of five species that were virtually restricted to
the upper intertidal stations at the SAND site are found in the upper righthand corner of Figure 33 (group 2).
These taxa are Hantzschia marina,
Hantzschia 1, Anorthoneis eurystoma, Amphora proteus and Navicula 16.
Taxa
that were most abundant at the mid-intertidal stations at the SAND site are
labeled as group 3.
These taxa were Gyrosigma prolorigum, Achnanthes
latestriata, Navicula forcipata, Amphora exigua, Cocconeis J, and Navicula
diversistriata.
Interspersed with members of group 3 were taxa that were
0
20
40
0
Figure 32.
4
4
60
EEE
E
I
20
E
EE
E
E
E
M= SILT(MUD)
F = FINE SAND
E
RA AXIS I
40
E
60
I
M
M
F
N
N
F
F
F
FF
F
MM
F
S5
S
SS
MF F F
F
MMMM
N
F
F
M Fl
80
M
F
F
SS
F
S
S
N
S
S
S
ss
-
S
100
S
S
Ordination of epiphyte and sediment-associated diatom samples by reciprocal averaging.
Samples were obtained from Zostera leaves (E), the SAND site (S), the FINE SAND (F),
and the SILT site (M).
E
EPIPHYTES
S= SAND
E
C
0'
60
40
RA AXIS
9
9
1
60
9
9
N-
9
8
7
80
777
6
76
77
68
8
66
8
58855
5
3434
44
333
2
I,J
Ordination of diatom species associated with the
epiphyte and sediment samples
illustrated in Figure 32. Numbers refer to
species groups discussed in the text.
20
III
9
9
N-
Figure 33.
0'
o
20
'40
4
4
(1)
c'J
80
.i.Is
In
I-
-16 2-
found in the sand samples, regardless of tidal height.
These species (group
4) included Navicula ammophila v. minuta, Amphora laevis v. perininuta, Amphora
be1lonitzschia hossamedinii.
libyca, Trachysphenia australis and
Iear the
right center of the figure, there are species that were common in the low
intertidal region at the SAND site.
These taxa (group 5) also were common at
the mid and low intertidal stations at the FINE SAND site.
These taxa were
Amphora tenerrima, Thalassiosira 1, Navicula 199, Achnanthes lemmermanni,
Navicula diserta, and Cocconeis placentula v. euglypta.
Amphora tenerrima and
Thalassiosira 1 were closely related to this group, but were classified as
members of group 9 because they were also common epiphytes.
Several taxa that
were common at the FINE SAND site also were common in samples from the SILT
site.
These taxa (group 6) were Amphora sabyii, Cocconeis hA, Achnanthes
hauckiana, Achnanthes 1, Navicula patrickae and Nitzschia punctata.
Four
other taxa were associated with this group but were classified as members of
group 9 because they were also found as epiphytes.
These taxa included
Navicula salinicola, Navicula 109, Nitzschia fundi, and Nitzschia frustulum V.
subsalina.
Taxa that were most abundant in the samples from the SILT site are
found at the lower right of Figure 33.
These taxa, classified as group 7,
were Navicula tripurictata, Opephora schultzi, Amphora 35, Nitzschia frustulum,
Nitzschia 2, Navicula gottlandica, Achnanthes 1IB, Amphora micrometra,
Navicula salina, Navicula groschopfi, Rhopalodia musculus, Fragilaria pinnata,
and Nitzschia 47.
Species that were common in all three sediments were placed
in group 8 and included Opephora pacifica, Opephora perminuta, Amphora
coffeiformis, Paralia sulcata, Cocconeis 11C, Navicula gregaria, and
Fragilaria striatula v. californica.
-163-
To obtain better resolution in the ordinations and to relate the sample
ordinations to patterns in the environmental data set, the data matrix was
divided into the epiphytic samples and the sediment samples, and an RA
ordination was performed separately on each data subset.
A plot of epiphyte samples relative to the first and second RA axes is
presented in Figure 34.
The samples from winter and spring are found on the
lower left of the diagram.
There was a change in community structure in June
that caused most of the June samples to be oriented in the upper left of the
figure.
The epiphyte samples from August and October are located on the right
end of RA axis 1, an orientation that also illustrated temporal changes and
discontinuities in species composition and relative abundance.
An RA ordination of epiphytic taxa corresponded closely with the pattern
of sample ordinations in Figure 34 and helped to illucidate the seasonal
changes in community composition (Figure 35).
The taxa on the lower left,
identified by four-letter acronyms, are Navicula directa, Gomphonema
oceanicum, Paralia sulcata, Rhoicosphenia curvata, Cocconeis scutellum, and
Cocconeis costata.
These taxa were spring and winter species that had a
maximum relative abundance in February or March.
Taxa that were abundant in
spring and summer are found in the upper left of the figure.
These taxa,
Berkeleya rutilans, Nitzschia frustulum v. subsalina, Cocconeis scutellum v.
arva, Nitzschia fundi, Navicula 109, and Cocconeis placentula v. euglypta,
were abundant from April through August and had maximum relative abundances
from May through July.
Taxa that were common from August through October are
found in the center of the diagram and to the far right.
Rhopalodia musculus,
Navicula 150, Melosira moniliformis, Melosira nummuloides, Bacillaria
20
40
F
-
Figure 34.
4
4
><
U)
c'J
60
J
A
A
J
D
A
20
F
0:
F:
4=
J:
U:
0=
JUNE
AUGUST
OCTOBER
APRIL
DECEMBE R
FEBRUARY
RA AXIS I
40
L!J
U
80
0
0
0
$00
U
Ordination of samples of epiphytic diatoms associated with Zostera leaves. The
ordination method was reciprocal averaging and the letters refer to the month
during which the samples were obtained.
F
J
4
4a:
(I)
ccos
PSUL
GOMO
RCUR
BRUT
CFR
Figure 35.
NDIR
CSUJ
C)
o
[SM
('.J
SFAS
NDIS
RA AXIS I
40
NPSU
NIT5
N150
RMUS
NROS
BPAR
NBRE
N171
Ordination of epiphytic diatom species associated with the
samples illustrated in Figure 34. The acronyms represent
the species discussed in the text.
NSCH
NSAL
NSUB
0
NFUN
MNUM
08
N109
001
VldD
Ui
-166-
paradoxa, Nitzschia 171, Opephora perminuta, and Nitzschia rostellata were
most abundant in October.
Synedra fasciculata, Navicula salinicola, and
Navicula tripunctata v. schizonemoides are found just below and to the left of
the center of the diagram and were abundant during all seasons.
An RA ordination of sediment samples and species resulted in a
distributional continuum that was related to sediment type.
The relative
positions of sediment samples and species were similar to the ordinations of
the entire data set (Fig. 32 and 33).
In order to interpret the distributions of samples and taxa in
relationship to the physical environment, PA axes from the sample ordinations
were correlated with environmental variables.
Two RA axes generated from an ordination of epiphyte samples were
correlated with tidal height, daylength, and water temperature (Table 32).
The highest correlations were between the second RA axis and daylength (r =
0.90) and between this same axis and temperature (r = 0.85).
axis is weakly correlated with the same variables (r < 0.25).
The first RA
Therefore, the
second axis is an expression of seasonal variation in the epiphytic flora,
while in the first axis is uninterpretable relative to these environmental
variables.
The examination of pattern in the sediment samples relative to the
physical environment also was investigated by correlation analysis (Table
33).
The first RA axis for the benthic samples was highly correlated with
sediment properties, as r = -0.75, -0.68, -0.77 for correlations between this
axis and organic matter, mean particle size, and the sorting coefficient,
respectively; the first PA axis was correlated, to a lesser degree, with the
chlorophyll ratio (r = 0.53).
-16 7-
Table 32.
Correlations between environmental variables and two PA axes
generated from an analysis of epiphyte data.
The environmental
variables are intertidal height (TIDE), daylength (DAYL), and
water temperature (TEMP).
The coefficient of determination (R2)
is given for the multiple regression of each PA axis against the
three environmental variables.
Correlation
Coefficients
Variable
TIDE
DAYL
TEMP
R2
RA1
RA2
-0.04
-0.05
-0.24
0.25
0.90
0.85
0.13
0.90
-168-
Therefore, this axis contrasts assemblages associated with fine sediments that
were poorly sorted, high in organic content, and with low chlorophyll ratios,
with assemblages associated with coarse, well sorted sediments that were low
in organic content and had high chlorophyll ratios.
The stations with high
chlorophyll ratios were the high intertidal stations, especially at the SAND
site.
The second RA axis was weakly associated with tidal height (r = -0.45)
and the chlorophyll ratio (r = -0.37).
This axis contrasts low intertidal
stations which had relatively low chlorophyll ratios with the high intertidal
stations.
A multiple regression analysis indicated that 76% of the variation in the
sediment sample scores for the first BA axis was associated with the nine
environmental variables (Table 33).
Approximately 46% of the variation in
sample scores for the second BA axis was associated with the same environmental variables.
However, weak correlations of this axis with etwironmental
variables made the interpretation of this axis uncertain.
-169-
Table 33.
Correlations between environmental variables and two RA axes
generated from an analysis of sediment diatom data.
The environmental variables are intertidal height (TIDE), chlorophyll a in
the top cm of sediment (CHLA), organic matter (OM), chlorophyll
ratio (RATIO), daylength (DAYL), water temperature (TEMP), mean
sediment particle size (PHI), the sorting coefficient (SORT), and
the skewness coefficient (SKEW).
The coefficient of determination
(R2) is given for the multiple regression of each RA axis against
the nine environmental variables.
Correlation
Coefficients
Variable
TIDE
CHLA
OM
RATIO
DAYL
TEMP
PHI
SORT
SKEW
R2
RA1
RA2
-0.01
-0.41
-0.75
0.52
0.03
-0.02
-0.68
-0.77
-0.07
-0.45
-0.15
-0.11
-0.37
-0.01
-0.03
-0.23
-0.25
-0.01
0.76
0.46
-170-
THE ZOSTERA PRIMARY PRODUCTION SUBSYSTEM
The research reported in this section examined the production dynamics of
a Zostera marina L. bed in Netarts Bay.
Specific objectives Included:
(1) a
description of the autecology of Zostera in Netarts Bay; (2) an investigation
of macrophyte-epiphyte relationships, and (3) the monitoring of the primary
production in Zostera and its epiphytes in the intertidal region over a
growing season.
Again, the process model presented in an earlier section
served as a conceptual framework for the research.
The results of the research on the Zostera Primary Production subsystem
are presented in six major subsections:
I - Materials and Methods; II -
Morphometrics and Autecology of Zostera marina L.; III
Production Dynamics
of Zostera; IV - Relationship Between Zostera and Epiphytic Assemblages; V Bioenergetics of the Zostera Primary Production subsystem; and VI Discussion.
Since many of the methods and materials for the study were
relevant to both the morphometric and production aspects of the research, such
information is presented in one introductory subsection, Subsection I.
In
Subsection II, patterns of sexual reproduction and vegetative growth of
Zostera in Netarts Bay are presented along with a general description of the
plant's natural history and autecology.
Subsections III, IV, and V are
concerned with the bioenergetics of Zostera marina and associated epiphytes.
I.
Materials and Methods
Description of Intensive Study Area
The EPA studies in Netarts Bay, reviewed above on pages
, were used
to generate hypotheses for further investigations at a finer level of resolu-
-171-
A detailed study of the vertical and horizontal nutrient profiles of
tion.
the water column over a transect from the channel through the seagrass beds to
the open mudflat was initiated by EPA.
Related biological aspects were
examined by the research presented in the next four subsections of this
report.
Interpretation of the results of the nutrient profile study in
relation to the biological processes study required that both aspects be
conducted during the same time period at the same location.
A site
appropriate for both projects was selected on the basis of the results of a
field study of the circulation pattern of water over the seagrass beds.
Criteria used in the selection included:
(1) the presence of a large expanse
of Zostera marina L. that was representative of the Zostera beds in the
estuary; (2) evidence of a straight line flow of water over the Zostera beds
during an incoming tide; and (3) accessibility for sampling.
The intensive study area in Netarts Bay included approximately 37,500 m2
located within the shellfish reserve and research area managed by the Oregon
State Department of Fisheries and Wildlife (Township 2S, Range lOW, in the
vicinity of Whiskey Creek).
This region lies near the north end of the large
intertidal Zostera bed that occupies the southern and western regions of the
bay (Fig. 36).
Three transects over a range of tidal heights were chosen within the
intensive study area.
38).
These were labeled transects 1 through 3 (Fig. 37 and
Transect 1 was 1.1
in
above MLLW and was located within the Zostera bed
away from the region of obvious influence from the channel.
The other tran-
sects were located during an incoming tide by placing a stake in the sediment
at the water's leading edge when the water at the next lower transect was
-17 2-
NETARTS BAY, OREGON
L
J
'44
C-)
0
0
0
Q
INTENSIVE STUDY
4REI
Figure 36. Location of Zostera beds and the intensive study area
in Netarts Bay.
-173-
z
75m /
/
ZOSTERA POND
cc'
SOUTH DRAJNAGE
C',
'CHANNEL
OLD
OYSTER
BEDS
I
-
TRANSECT
1
j
NORTH
DRAINAGE
MAIN CHANNEL
Figure 37. Map of the area of intensive study, indicating the
location of the sampling transects relative to the
main channel.
/
0
40
80
120
DISTANCE IN METERS
(+1.lm)
160
200
240
TRANSECT 3 (+1.4m)
i TRANSECT 2 (1.2m)
TRANSECT
-
Figure 38. Cross section of the area of intensive study indicating the location and
height of the sampling transects.
/
ZOSTERA BED
ii
OPEN MUDFLAT
-17 5-
15 cm deep.
This procedure located transect 2 at 1.2 m above MLLW, and
transect 3 at 1.4 m above MLLW.
Transects 1 and 3 represented the upper and
lower limits of the Zostera bed within the intertidal region; transect 2
represented a region of transition.
Moreover, transect 2 was at the edge of a
large pool of water that was created at low tide by the damming effect of the
larger Zostera shoots in the area.
Therefore, this transect was located
between an area that was regularly exposed at low tide, and one that did not
drain completely at low tide.
The transects were established by positioning stakes with an Abney level
and measuring tape at 5 m intervals at the appropriate elevation.
Transects
1, 2, and 3 were 75 in, 100 m, and 100 m in length, respectively.
The ends of
the transects were located away from any obvious influence of the drainage
channels that bordered the study area.
The elevation at each transect was
checked relative to predicted values for the height of the high tide for
Tillamook County beaches.
Stakes marked at
1
cm intervals along their length
were placed in the channel at the intensive study area and at each of the
transects.
The difference in the depth of the water in the channel at slack
low tide and at the following slack high tide was determined, and the depth of
the water at each transect was measured.
The ratio between the predicted
height of the high tide and the measured height was used to calculate the elevation of each transect relative to MLLW.
A series of 0.5 x 0.5 m sample sites were designated along each transect.
Transect 1 had 150 sample sites and transects 2 and 3 each had 200 sample
sites.
The sites to be sampled along each transect on a particular date were
chosen from a random number table without replacement.
Individual random
number tables of the proper size for each transect were generated by a
computer using a random iterative process.
-176-
Selection of Quadrat and Sample Size
Choice of quadrat size and sample size for biomass determinations was
based on data collected during the 1979 growing season.
Quadrats larger than
400 cm2 were considered unsuitable because the large biomass from such a
quadrat limited the number of replicates that could be processed before the
material deteriorated.
Quadrat sizes from 100 to 400 cm2 were tested.
Counts
of shoot density along each transect were used as an indicator of the variance
among biomass samples.
These counts were taken at the beginning and end of
the growing season, i.e., in June and September.
In general, variance at all
transects decreased with an increase in quadrat size from 100 to 400 cm2
(Table 34); 400 cm2 (20 x 20 cm) quadrats were used for all subsequent
samples.
The harvest of a 400 cm2 quadrat did no obvious, lasting damage to
the system.
During the subsequent growing season, harvested areas were
recolonized by vegetative shoots from neighboring regions.
The shoot density data from June and September 1979 also was used to
select a suitable sample size.
Factors considered in choosing the number of
quadrats per sample for each transect included the level of precision of the
estimate of the mean of the biomass, and the cost in time and materials of
processing the samples.
For the intensive study area, it was determined that
a sample size of seven 400 cm2 quadrats had a standard error that was less
than 207. of the mean (Table 34).
Also, seven quadrats per transect could be
harvested by one person during the low tide in two or three consecutive days.
In 14 days or less, the plant material from seven 400 cm2 quadrats per transect could be processed to the point where it could be stored indefinitely
without deterioration until all necessary measurements could be made.
This
STANDARD ERROR
= X% OF MEAN
STANTARD ERROR
MEAN
SEP TEMBER, 1979
12
6
3
21
12
18
140
112
182
24
44
81
92
14
762
22
900
25
847
32
90
721
10
109
170
410
300
710
10
443
200
529
100
686
12
117
130
138
400
1236
300
1238
1
1186
200
657
11
104
STANDARD ERROR
STANDARD ERROR
= x% OF MEAN
957
100
MEAN
JUN E, 1979
TRANSECT
2
QUADRAT SIZE (cm )
24
310
108
11
1286
28
23
265
1143
25
18
188
206
20
1025
19
1052
23
193
208
224
333
400
1007
300
919
3
879
200
1171
100
954
19
99
518
400
Table 34. Sample statistics from shoot density data used to determine quadrat size (n = 7).
-17 7-
-178-
was an important consideratthn in choosing a sample size, because fresh
samples of Zostera could not be refrigerated longer than 14 days without
significant deterioration.
Therefore, the standard sample size selected for
this study was seven quadrats per transect.
Howeve r, depending on weather
conditions, time and help available for field work,
and the biomass of the
Zostera, as few as five quadrats at a transect were sampled at certain times.
Measurement of Biomass
The intensive study site was visited monthly from May 1979 through June
Biomass samples were taken monthly from April 1 to September 8, 1980,
1981.
on February 12, 1981 and between April 6 and May 31, 1981.
Individual sample sites were located by extending a 5 m rope marked at
0.5 m intervals between two of the stakes along a transect (Fig. 39).
A 20 x
20 cm quadrat frame made of polyvinyl chloride (PVC) welding rod was
positioned on the right-hand side of the site, approximately 10 cm back from
the rope (Fig. 39B).
Shoots inside the quadrat were moved away from the
edges, and the sediment and rhizome mat along the outer edge of the quadrat
were cut through a trowel.
Zostera and associated sediment were then placed
in a 1 mm mesh sieve, and the sediment washed from the roots with water.
Therefore, coarse particulate organic matter (CPOM) was retained where CPOM
was defined as particles larger than 1 mm in diameter.
Plants with associated
epiphytes were put in labeled plastic bags with a minimum of water, while the
litter was retained in the sieve.
The remaining sediment in the quadrat was
dug out to a depth of about 20 cm below the rhizosphere and was added to the
sieve.
The sand was washed from the sieve and the remaining litter material
was placed in a labeled plastic bag.
All material was kept on ice until it
could be refrigerated after returning to the laboratory.
-'79-
TRANSECT SEGMENT NUMBERS
200
80
190
I7
80
160
70
60
50
40
1
I
I
30
I
20
10
0
I
/
STAKES AT 5m INTERVALS
ALONG A lOOm TRANSECT
60
70
70
á9 I
I
t
I
63 62 61
I
67
66
I.
A 5m INTERVAL WITH 10
O.5rn TRANSECT SEGMENTS
A O.5m TRANSECT
SEGMENT
(Th
---- I
H
ROPE WITh MARKERS
A = AREA USED FOR SHOOT PRIMARY PRODUCTION MEASUREMENT
B = PLACEMENT OF 400 cm2 QUADRAT FOR BI0?AASS SAMPLE
Figure39. A 100-rn sampling transect at three levels of spatial
I. 200 0.5-rn transect segments; II. 5-rn
resolution:
segment of transect with 10 0.5-rn transect segments;
The details of one sampling site at a
and III.
transect segment.
-180-
During the time each sample was taken, selected physical properties of
the bay and ocean water were measured.
with a hand-held thermometer.
Surface water temperature was measured
A temperature compensated A0 Goldberg
refractometer was used to determine salinity.
Light intensity at the water
surface and at a depth of 0.25 in were measured with a LICOR Underwater
Photometric Sensor and Quantum Radiometer Photometer.
These values were used
to calculate extinction coefficients.
Zostera bioniass from each sample quadrat was divided into a series of
subsamples to reduce the biomass of the material to be handled at one time and
to minimize exposure to room temperature.
Each subsample was placed in a 1 mm
mesh sieve, and individual shoots were cut from the rhizome at the nodes.
This material was transferred to a second 1 mm mesh sieve along with loose
leaves, shoots and seedlings.
The sieve containing the leaves, shoots and seedlings, i.e., the aboveground material, was carefully dipped several times into a basin of distilled
water to rinse away salt and any remaining sand.
the following information was recorded:
The shoots were sorted and
the number of vegetative shoots,
reproductive shoots, and seedlings; the number of leaves per vegetative shoot;
and the number of leaves and flowers per reproductive shoot.
Leaves were cut
from their sheaths, and the sheaths were placed into labeled 55 x 15 mm
aluminum weighing dishes.
20 mm plastic petri plate.
These containers had been bent to fit inside a 60 x
To minimize handling errors, a weighing dish was
kept inside a petri dish unless a weight was being determined.
The leaves
were laid out on a labeled 20 x 20 cm glass plate until an area of
approximately 16 x 20 cm was covered.
The length and width of the area
covered were measured to the nearest 0.5 cm and recorded.
The glass plates
-18 1-
were covered with leaves and then were coated with distilled water, placed in
When the water was frozen, the
wooden racks and transferred to a freezer.
plates were wrapped in aluminum foil and stored in a freezer.
shoots were processed in the same manner.
Reproductive
Stems and flowers were combined
with the sheaths from the vegetative shoots.
The sieve with the belowground material, i.e., roots, rhizomes and
litter, was thoroughly washed in a basin of tap water to remove any remaining
sand, and then was dipped several times in distilled water to complete rinsing
away the salt.
Material from this sieve was sorted by inspection into living
and dead roots and rhizomes, and each fraction was placed into labeled
containers.
Other detritus in the sieve was combined with dead rhizome
material, along with unsprouted Zostera seeds.
Notes were taken on the
quality of the litter.
All sorted material was kept frozen and stored until it was lyophilized.
The process of lyophilization was of particular importance because it
facilitated the removal of epiphytes from the leaves (Penhale, 1977).
After
lyophilizing, epiphytes were removed from the leaves and glass plate with a
scraper made from a plastic coverslip glued between two glass microscope
slides with 3-4 mm of Its edge protruding.
Epiphytes and leaves were each
placed in containers and the dry weight of all sorted lyophilized material was
determined.
To determine the ash-free dry weight of the leaves, sheaths, roots and
rhizomes, and epiphytes, all the material of one kind from the sample quadrats
at a transect was combined and ground to a powder in a Waring blender.
This
homogenized material was subsampled to fill a maximum of three porcelain
crucibles (COORS, size 0).
The naterial in the crucibles was weighed, ashed
-182-
for 48 hours at 500°C in a muffle furnace, and reweighed to determine the
weight of the ash.
To determine the time necessary to completely ash the
material, crucibles with organic matter were repeatedly ashed until they came
to constant weight.
The difference between the dry weight of the material
before ashing and the weight of the ash was recorded as ash-free dry weight.
Measurement of Primary Production
1.
Shoot Marking Method
Net primary production of Zostera shoots were measured by a modified
shoot marking technique (Zieman, 1974).
Biweekly samples of 14 to 15 shoots
per transect were taken, with two or three shoots marked at each sample site
(Fig. 39A).
Individual shoots typical of the area were selected.
A 0.5 m
stake of white PVC welding rod bent into a ring at one end was inserted into
the sediment, and the base of a shoot was encircled with the ring.
Another
PVC stake extending 15 cm above the sediment was placed in the area of the
marked shoots to make the region easy to locate, since the PVC rings at the
sediment surface were not readily visible (Fig. 40A).
Each shoot was marked
by inserting a 22 gauge hypodermic needle above the level of the youngest
sheath through all the leaves at the same time.
The distance between the PVC
ring at the base of the shoot and the needle was measured to the nearest
0.5 cm.
After the needle was removed, the number of leaves and lateral shoots
were counted.
A marker was placed midway along the length of the next to
youngest leaf (Fig. 40B).
This marker, made from a 20 cm length of one pound
test nylon monofilament, had a loop formed by a slipknot at one end; a 1 cm
-183--
NEEDLE
LEVEL OF
NEEDLE MiRK
DISTIANCE
RECORDED
.PLASTIC
BEAD
SU PKNOT
Figure 40. Shoot marking technique. A. Zostera shoot with next
to youngest leaf marked with monofilament line. B.
The monofilament leaf marker with plastic bead.
-184-
length of 15 pound test monofilament was glued to the other end to serve as a
needle.
To make the marker more visible, a plastic colored bead was threaded
onto the line and glued in place below the slipknot.
The needle end of the
marker was passed through the leaf and through the loop at the other end.
The
loop then was pulled closed, securing the marker in place around the leaf.
After 12 to 16 days, the shoots were harvested at the level of the PVC ring,
and placed in individual, labeled plastic bags until they could be refrigerated at the laboratory.
At the same time, new shoots were marked for the
next two-week period.
In the laboratory, individual shoots were rinsed in distilled water to
remove sand and salt.
The leaf with the plastic marker was located; and the
number of leaves present, the number of new leaves, the number of leaves lost,
and the number of lateral shoots were determined (Fig. 41).
The length and
width of each leaf above its sheath was measured relative to its position on
the shoot.
Then the distance from the base of the shoot to the original
location of the needle mark was measured, and the leaves were cut free at this
point.
If the PVC ring obviously had moved during the incubation time, the
level of the needle mark in the oldest leaf was used as the reference point,
as this leaf usually did not grow during the measurement period.
Leaves were
laid out in the order of their age, and their needle marks were located.
The
distance between the original level of the mark (i.e., the cut end of the
leaf) and its new position was the leaf's contribution to net primary production.
This new growth was removed from the leaf and placed on a 20 x 20 cm
labeled glass plate.
The length and width of this tissue were measured
relative to the position of the leaf on the shoot.
Glass plates with this
ARDED
1
p-YOUNGEST LEA
IF FOUR LEAVES WERE MARKED ORIGINALLY THEN:
LEAF WAS SLOUGHED
1
LEAF WAS PRODUCED
OLDEST
Figure 41. Shoot marking technique indicating the above-ground net primary production (new growth)
and leaf export.
SHOOT CUTOFF AT
LEVEL OF PVC RING
DIS
ORIGINAL-LEVEL
)F NEED LE MARK
NEW GROWTH
= NEEDLE MARK
-185-
material were treated in the same manner as those processed with Zostera
leaves for the biomass determination.
Epiphytes removed from the leaves were
discarded, and the dry weight of the new growth per shoot was determined.
2.
Radioactive Carbon (14C) Method
The relative net primary production of Zostera and the epiphytes was
based on in Situ 14C incorporation measurements (Wetzel, 1974).
The Bittaker
and Iverson (1976) design for an incubation chamber was adapted for use with
this method.
This chamber also was used for the measurement of algal primary
production; its structure is described in an earlier section of this report
(Fig. 8).
Light and dark chambers were used for the field measurements.
Light chambers were constructed of transparent, tubular Plexiglass, while dark
chambers were constructed of white, tubular Plexiglass.
The exterior of each
dark chamber was painted silver and wrapped with silver duct tape to insure no
leakage of light.
The '4C-sodium bicarbonate (NaH14CO) used was obtained from New England
Nuclear Corporation as a powder with a specific activity of 7.5 mCi/mmol.
The
powder was dissolved in sterile, distilled water in a stoppered volumetric
flask.
This solution was standarized in April, 1982 and was stored at 5° C
until use.
At each transect, measurements were obtained from two light chambers and
one dark chamber.
Monthly measurements were made from June 29 to August 24,
1980 and on May 31, 1981.
selected.
At each sample site a clump of Zostera was
A 30 cm length of PVC pipe (i.d. = 10.5 cm, o.d. = 11.5 cm) was
placed around the clump and was inserted into the sediment until about 2 cm
remained above the surface.
To contain the leaves of the Zostera shoots, a
bag made of nylon was fastened around the top of the pipe with a rubber
band.
When the water from the incoming tide was approximately 50 cm deep at
the sample site, the incubation unit of the chamber was positioned around the
net and the PVC pipe.
Next, the net was removed, and the incubation unit was
inserted 30 cm into the sediment.
When the incubation unit filled with water,
the stirring unit was attached, thereby sealing the chamber.
Then 7.3 11Ci of
a standardized solution of NaH14CO3 solution was injected into the incubation
unit and the time was recorded.
An external water sample was taken, fixed
with mercuric chloride, and later the total available inorganic carbon in the
sample was determined by the EPA Water Testing Laboratory using a split beam
infrared spectrometer.
During the incubation period, light intensity (PE
m2 s1)
was measured
continuously using a LICOR Spherical Quantum Sensor and Printing Integrator.
In addition, salinity, surface water and air temperature, and light intensity
at the water surface and at a depth of 25 cm were measured hourly over the
Zostera bed.
After a period of 4 to 7.5 hrs, the stirring unit was removed, and the
time was recorded.
The incubation unit then was pulled from the sediment, and
the PVC pipe containing the incubated core of Zostera was removed.
The
Zostera core was transferred to a 1 mm sieve, and the associated sediment was
washed away from the roots and rhizomes.
The Zostera was rinsed in distilled
water to remove the salt, wrapped in foil, placed in a labeled plastic bag,
and frozen quickly on dry ice.
Samples were stored in a freezer until they were lyophilized.
Zostera was sorted into roots and rhizomes, leaves, and epiphytes.
Dried
The dry
-187--
weight of each fraction was determined.
Samples were then exposed to
concentrated HC1 fumes to remove residual labeled inorganic carbon (Allen,
1971).
Material from each sample was ground to a powder in a Waring blender
and subsamples of 0.1 to 0.2 g were placed in filter paper cones and
compressed into pellets.
The pellets were combusted in a Packard TRI-CARB
Oxidizer (Model 306) where evolved CO2 was chemically trapped in 4 ml of
Packard CARBOSORB.
This was transferred into a scintillation vial with 12 ml
of Packard PERMAFLUOR V.
The vials were counted in a Packard TRI-CARE Liquid
Scintillation Spectrometer System (Model 2425).
Counts were corrected for
recovery from the oxidizer (92% for Zostera, 91% for epiphytes), counting
efficiency (59% for aboveground Zostera, 56% for belowground Zostera, 54% for
epiphytes), and background.
Assimiliation of '2C was calculated according to
an equation of Pehale (1977), but disintegrations per minute (dpm) were
substituted for counts per minute (cpm).
Data Analysis
Morphometric and biomass data were analyzed by multiple regression
analysis (Snedecor and Cochran, 1967) and principal components analysis
(Cooley and Lohnes, 1971).
Data analyses were performed on a Control Data
Corporation CYBER 170/720 computer at the Oregon State University Computer
Center.
The computer programs used were part of the REGRESS and MULTIVARIATE
subsystems of the Systems Interactive Programming System (SIPS).
II.
Morphometrics and Autecology of Zostera marina L. in Netarts Bay
The vegetative shoot of Zostera marina L. comprises an extensive rhizome
system that bears erect, leafy shoots.
The linear leaves with basal sheaths
EB
are 3-12 mm broad and up to 12 dm long (Hitchcock and Cronquist, 1973).
The rhizome has a meristem associated with each leaf that is positioned
immediately below the node (Tomlinson, 1974).
At each node two bundles of
Since Zostera persists in natural habitats primarily
roots are formed.
through vegetative reproduction, a continually active meristem is necessary to
maintain the populations.
(Tomlinson, 1974).
This requirement is termed meristem dependence
The shoot apical meristem produces leaves dichotomously,
giving the shoot a laterally, flattened appearance.
An internode remains
small until the leaf associated with one of the nodes becomes the next to the
oldest leaf on the plant.
At this time the internode elongates, and the roots
are produced at the node.
Consequently, the shoot is pushed ahead through the
sediment by the growth of the youngest internodes along the rhizome.
The life
of an internode is about 90 days during the growing season in North Carolina
(Kenworthy, personal communication).
New shoots are produced by the
development of axillary buds in the nodes of the oldest leaves.
With the loss
of the leaf whose node produced it, and with the branching of the rhizome,
these shoots become independent from the parent shoot.
Sexual Reproduction
Events in the life of Zostera marina L. occurred with seasonal regularity
in Netarts Bay.
Seeds were found in the sediments throughout the year, but
gerimination was restricted to spring (Fig. 42, Table 35), starting between
mid-February and early April, and concluding by the end of June.
Seedlings
were not found in the sample taken on February 12, 1981, but were present at
all transects in the samples taken in early April 1980 and 1981.
They dis-
Figure 42.
2:
ii
20
50
APR1
MAY2
Density of seedings along
Each point represents the
Lu
0
(I)
z70
-J
a
w6O
Lu
(9
(I)
CsJ
-90
100
DATE
JUN29 JUL26 AUG24 SEP24
TRANSECT 3 (-ft4m)
the three transects during the 1980 sampling period.
mean of 5 to 7 observat ions.
JUNT
[I
TRANSECT 2 (+ 1.2 m)
N TRANSECT 1 (+1.lm)
SEEDLING DENSITY
(8)
36
(13)
(9)
25
(14.4)
FEB 12
SEP 24
0
AUG 24
1980
JUL 26
JUN 29
0
C
0
0
0
0
0
0
C
0
(11)
25
29
60
(15)
21
4
(4)
79
(26)
JUN 1
86
MAY 2
(22)
APR 1
0
I
Dashes indicate no data available.
TRANSECT
21
(10)
5
(5)
25
(14)
25
(25)
85
(19)
70
MAY 30
(24)
1981
MAY 3
APR 6
Table 35. Mean number of seedlings per square meter during the period from April 1980 through Ma! 1981.
Values in parentheses represent the standard error of the mean of 5 to 7 observations."
-190-
C
0
-19 1-
appeared from the samples at all transects by the end of June.
Moreover,
seedling data indicated that sexual reproduction did not play a major part in
the growth and maintenance of the Zostera bed in Netarts Bay.
This is compat-
ible with the conclusion of McRoy (1966) and Phillips (1972).
However,
although the majority of the new shoots are produced by vegetative reproduction, the seedlings are probably important to the maintenance of the genetic
diversity within the population.
At no time did seedlings represent more than
7% of the shoot population at all transects (Table 36).
The mean percentage
of the total shoot density that was represented by seedlings when they were
present was 2.7% (S.E. = 0.4%).
In samples obtained during 1980 and 1981, the presence of reproductive
shoots was variable (Fig. 43, Table 37).
present from April to September.
In 1980, flowering shoots were
In the low intertidal region, reproductive
shoots were first seen in April, extending up to the mean tidal height of the
winter higher low tide.
Flowers were seen throughout the bed in May, and they
first appeared in the samples on June 1 at transect 1 and on June 29 at transects 2 and 3.
September 24.
Flowers were absent in the samples taken from all transects on
In 1981, reproductive shoots observed during February in pools
at the higher intertidal region (+1.4
in
above MLLW) did not become numerous
enough to appear in the samples until May 30.
Data related to reproductive
shoot densities also suggested that sexual reproduction did not play a major
role in the growth and maintenance of the Zostera bed in Netarts Bay.
When
present, reproductive shoots representd no more than 6% of the total shoot
density at all transects (Table 38).
The mean percentage of the total shoot
density that was represented by flowering shoots when they were present was
2.6% (S.E. = 0.5%).
0
0.2
3.1
3.1
3.7
5.1
6.7
3.0
2.7
3.2
1
2
3
Dashes indicate no data available.
0
0
JUN 1
MAY 2
TRANSECT
APR 1
0
0
0
1980
JUL 26
JUN 29
0
0
0
AUG 24
0
0
0
SEP 24
FEB 12
2.2
1.8
0.5
2.5
1981
MAY 3
APR 6
Table 36. Percentage of the total shoot density represented by seedlings during the period from
April 1980 through May 1981. The percentages were calculated from the ratio of the
means of 5 to 7 observations.
-19 2-
1.8
0.7
MAY 30
7o
4o
Figure 43.
APR 1
S
MAY2
JUN 1
TRANSECT 1(-i-1.lm)
TRANSECT2(12m)
TRANSECT 3(+14m)
JUN29 JUL26 AUG24 SEP24
DATE
REPRODUCTIVE SHOOT DENSITY
Density of reproductive shoots along the three transects during the 1980
sampling period. Each point represents the mean of 5 to 7 observations.
zIo
co
w
c3O
IL
0
w
0
0::
>
IiJ
(I)
U)
Ig6o
csJ
TRANSECT
0
0
1980
JUN 29
JUL 26
11
(7)
25
50
(21)
C
Dashes indicate no data available
N
(17)
I
32
(7)
1981
APR 6
I
(50)
14
29
FEB 12
SEP 24
C
(5)
5
AUG 24
C
(41)
(13)
C
(20)
C
(7)
C
40
0
65
0
39
JUN 1
MAY 2
0
APR 1
0
MAY 3
(28)
100
(19)
40
MAY 30
Table 37. Mean number of reproductive shoots per square meter during the period from April 1980 through
Values in parentheses represent the standard error of the mean of 5 to 7 observations.
May 1981.
-194-
C
I
C
C
C
C
o
0
Dashes indicate no data available.
1.9
0
Z
JUN 1
0
0
1
MAY 2
3.0
3.0
3.4
0.8
1.0
2.8
1980
JUN 29
JUL 26
5.3
2.8
0.5
AUG 24
1.1
5.7
MAY 30
MAY 3
FEB 12
SEP 24
0
0
0
APR 1
0
0
TRANSECT
Percentage of the total shoot density represented by reproductive shoots during the period
from April 1980 through May 1981. The percentages were calculated from the ratio of the
means of 5 to 7 observations. *
0
-
0
Table 38.
-19 5-
0
-
0
0
-
0
IdV
0
9
1861
Vegetative Growth
Because the majority of the shoots in the bed at any time were vegetative, the results of this study related primarily to the biology of the
vegetative shoots of Zostera marina in Netarts Bay.
Short, narrow leaves were produced by each shoot in the autumn, and in
this form the plant survived the winter.
In Netarts Bay the change to the
winter morphology began in September and was complete at the upper intertidal
transects (2 and 3) by the end of November and at transect 1 by the end of
December.
Growth in the leafy portions of the plant resumed sometime in late
February or March when the transition from the narrow-bladed form to the
broader-bladed form occurred.
The winter leaves were systematically sloughed
off as the summer leaves were produced.
The leaves produced during the period
of transition were usually 1-2 mm wider at the base than at the tip, while the
summer leaves had a uniform width along their entire length from May until the
change to the winter morphology began in September.
There was a regular pattern in the production and sloughing of leaves
from vegetative shoots in Netarts Bay.
The time interval between the
initiation of two successive leaves on one shoot was termed the plastochrone
interval (PT).
The Pt for the period between samples was calculated from the
expression proposed by Jacobs (1979):
number of shoots marked X observation period in days
number of new leaves on marked shoots
-19 7-
The time interval between the sloughing of two successive leaves on one shoot
was termed the export interval (El).
The average El for a sample period was
calculated from the expression:
number of shoots marked X observation period in days
number of leaves sloughed from marked shoots
Trends for the entire growing season were examined by using data from
transects 1 and 3 from June through October 1980, and from April through June
1981 (Table 39).
The value of the Pt ranged from 7.0 to 25.6 days, while the
value of the El ranged from 7.1 to 23.3 days.
In general, the P1 was shorter
than or equal to the El during April and May.
This resulted in an increase in
number of leaves per shoot during that period, because leaves were being
produced faster than they were being shed.
From June through October, the
trend reversed and the El was shorter than the Pt.
The net result of this
pattern was a reduction in the number of leaves per shoot, since during that
period leaves were lost faster than they were produced.
A plot of the average
number of leaves per shoot against time illustrated the effect of these
patterns for the entire growing season in 1980, and for the time measured in
1981 (Fig. 44).
The relatively low number of leaves per shoot determined for
June 29, 1980 was probably due to experimental error, as inexperienced new
workers were involved in the laboratory work at that time.
There was little
correlation between number of leaves per shoot and other variables associated
with Zostera and its epiphytes (Table 40).
Therefore, the number of leaves
per shoot was not a linear function of these other variables, but instead, was
more closely related to changes in the P1 and El.
-19 8-
Table
39. Mean plastochrone
interval (P1) and mean export interval
expressed as days for the period from June 1980
through June 1981. Values listed are the means of 14
or 15 observations.
(El)
TRANSECT
1
TRANSECT
P1
2
El
TRANSECT
P1
3
El
P1
El
14-29
15.0
10.0
8.3
13.6
9.0
7.9
JUN 29-JUL 13
21.0
8.8
12.9
10.0
13.3
10.7
13-26
18.0
12.0
14.4
14.4
13.0
11.4
JUL 26-AUG 12
25.0
16.0
20.0
12.8
14.2
9.1
12-24
16.5
19.0
14.7
11.0
21.7
10.8
AUG 24-SEP 8
17.0
19.0
16.0
13.1
11.7
16.0
8-24
25.6
16.0
19.6
11.0
SEP 24-OCT 7
22.0
15.0
19.6
12.3
10.5
7.6
7-23
19.0
15.0
12.4
11.4
18.0
18.0
6-18
9.0
15.0
10.0
14.0
APR 18-MAY 3
9.5
9.4
7.0
18.7
MAY
3-16
12.2
11.8
8.0
7.8
MAY
16-30
10.0
11.7
7.0
23.3
MAY 30-JUN 17
13.0
8.5
9.4
7.1
18.0
11.6
10.5
8.4
1980
JUN
JUL
AUG
SEP
OCT
1981
APR
-u
JUN
*
17-JUL 1
Dashes indicate no data available.
Figure 44.
APR I
JUN29 JUL26 AUG24 SEP24
DATE
MAY2 JUN 1
TRANSECT2 (1.2m)
TRANSECT3(+1.4m)
TRANSECT 1 (+1. im)
Average number of leaves per vegetative shoot at the three transects during the period from
April through September, 1980. Each point represents the mean of 5 to 7 observations.
0
z2
m
Lu
Li.
0
Lu
-J
>
Lu
LI-
Iii
U)
I
0
0
F-
ru
LEAVES PER SHOOT
-2 00-
Table4O. Correlation coefficients (r) relating the number of
leaves per shoot to selected variables. Values
greater than 0.2 are significantly different than
zero where P < 0.01.
Variables
Total shoot density (shoots
m2)
0.166
2
Average area of a vegetative leaf (cm )
-0.253
Aboveground biomass (g dry wt. m2)
0.075
m2)
0.005
Belowground bioinass
(g dry wt.
Total Zostera biomass (g dry wt. m
-2
Epiphyte biomass (g ash-free dry wt.
0.045
)
m2)
Epiphyte leaf (g dry wt. epiphyte/g dry wt. leaf)
0.010
0.072
-20 1
The P1 measured the average length of time that a leaf spent in each
position on a shoot.
Therefore, the PT multipled by the mean number of leaves
per shoot equalled the average lifetime of a leaf on a shoot.
To examine the
changes in the length of the lifetime of a leaf, the sampling period was
divided into growth phases according to changes in the ratio between the P1
and the El (Table 41).
Plants along transect 1 exhibited three phases.
In
April, the P1 (9 days) was shorter than the El (15 days), in May the P1 and El
were equal (each 12 days), and from June through October the P1 (20 days) was
longer than the El (15 days).
Transect 3 had two phases.
In April and May
the P1 (9 days) was shorter than the El (13 days), and from June through
October the Pt (14 days) was longer than the El (11 days).
Transect 2 was
only measured from June through October when the P1 (15 days) was longer than
the El (12 days).
The average lifetime of a leaf was calculated for each
phase for each transect (Table 42).
Comparison of the lifetime of a leaf for
each transect revealed that from June through October, leaves remained on the
shoots in the lower intertidal region (transect 1) longer than they did on
shoots in the upper intertidal region (transects 2 and 3).
In general, the
time a leaf remained on a shoot increased from April to September.
Growth of a leaf in relation to Its age or position on the shoot also was
anlayzed.
Data were standardized by expressing the amount of growth of each
leaf as a proportion of the total growth of the shoot.
Since the absolute age
of each leaf measured was not known, relative ages were used.
The youngest
leaf on a shoot was designated as number one, and each successive leaf was
numbered in order from the youngest to the oldest.
This avoided problems when
comparing shoots with different numbers of leaves, because any group of leaves
-2 02-
Table 41. Mean plastochrone interval (P1), mean export interval
(El), and mean number of leaves per shoot (LVS) for
periods from April to June, 1981 and from June to
P1 and El are expressed as days. The
October, 1980.
values in parentheses represent the standard error of
the mean for 9 to 26 observations.
1981
APRIL TO JUNE
TRANSECT
P1
El
LVS
12.0
11.4
(1.4)
(0.9)
3.7
(0.1)
3
TOTAL
BED
-
1980
JUNE TO OCTOBER
P1
El
LVS
2.8
19.9
14.5
(1.3)
(1.2)
(0.1)
-
15.3
12.3
(1.3)
(0.5)
2.7
(0.4)
4.0
8.7
(0.6)
13.2
13.9
11.4
(2.7)
(0.1)
(1.5)
(1.3)
10.3
12.3
12.8
(1.4)
3.9
(0.1)
16.5
(0.9)
(0.9)
(0.8)
Dashes indicate no data available.
2.9
(0.1)
2.9
(0.1)
-203-
Table 42. Mean lifetime of a leaf (days) for each transect during
the growing season. P1 = mean plastochrone interval;
El = mean export interval; LVS = mean number of leaves
per shoot.*
PI<EI
PI=EI
PI>EI
TRANSECT 1
Period
P1
LVS
Lifetime
April
9.2
3.7
34.0
May
11.1
3.6
40.0
June-October
19.9
2.8
55.7
TRANSECT 2
Period
P1
LVS
Lifetime
-
-
June-October
15.3
2.7
41.3
TRANSECT 3
Period
P1
LVS
Lifetime
April-May
8.7
4.0
34.8
Dashes indicate no data available.
June-October
13.9
2.9
40.7
-204-
in the same position relative to the youngest leaf on their respective shoot
were approximately the same age.
At all transects throughout the study the
greatest proportion of growth occurred while a leaf was in position 2 (Table
43).
During the first phase of growth (April and May) the youngest and next
to youngest leaf accounted for 48 to 65% of the total growth of the shoot.
During the last phase of growth (June to October), these leaves accounted for
75 to 95% of the growth of the shoot.
As the growing season progressed, the
number of leaves per shoot decreased, the Pt became longer, the average
lifetime of a leaf became longer, and an average leaf spent more time in each
position.
Therefore, as fall approached, more of the growth occurred at
positions 1 and 2 and less occurred at position 3, and more than half of the
total growth of a shoot was due to the growth of leaves two Pt or less old.
III.
Production Dynamics of Zostera
Biomass
The general pattern for the accumulation of the total biomass of Zostera,
i.e., the summation of aboveground and belowground biomasses, was similar at
transects 1 and 3 (Fig. 45).
In 1980, total biomass increased along both
transects through the spring to a maximum in July, and then declined (Table
44).
The maximum total biomass at transect 1 was 463.1 g dry weight if2,
while that at transect 3 was 142.8 g dry weight if2.
the rate of increase of total biomass at transects 1
rate of increase in the spring of 1980 (Table 44).
In the spring of 1981,
and 3 was higher than the
Total biomass at transect
1 on May 30, 1981 was equivalent to that on June 29, 1980.
Total biomass at
transect 3 on May 30, 1981 was equivalent to that on July 26, 1980.
In
-205-
Table 43.
Percentage of total shoot growth distributed among
youngest
leaves of different relative ages,wherel
leaf on shoot. Values in parentheses represent the
standard error of the mean of 14 or 15 observations.
APRIL-MAY
JUNE
JULY-OCTOBER
TRANSECT 1
% 1
21.0
33.7
(1.4)
(3.8)
(1.9)
46.3
50.0
%
2
41.3
(2.6)
(2.6)
%
3
28.5
19.0
% 1 + 2
%
1 + 2 + 3
41.5
(1.3)
(1.5)
(1.7)
8.5
(1.3)
64.8
80.0
91.5
(0.5)
(2.1)
(1.3)
93.3
99.0
99.9
(1.3)
(0.6)
(0.1)
TRANSECT 2
c
35.9
% 2
48.4
% 3
13.6
%1+2
84.3
%l+2+3
97.9
(2.2)
(2.0)
(2.3)
(3.6)
(1.3)
TRANSECT 3
27.1
14.3
25.7
(2.8)
(4.3)
(3.8)
% 2
34.3
43.7
48.1
(2.0)
(3.2)
(1.2)
3
32.5
24.3
22.1
%
%
1
(1.9)
(4.3)
(3.0)
% 1 + 2
48.5
72.7
(4.0)
(2.0)
% 1 + 2 + 3
81.0
96.7
(3.5)
(2.0)
75.3
(3.7)
97.4
(0.9)
Dashes indicate no data available.
321.8
(31.4)
269.9
(12.4)
259.5
(26.8)
(38.2)
(5.0)
(19.3)
88.7
142.8
103.6
65.4
45.4
(12.0)
(24.3)
(23.4)
64.5
(13.9)
128.0
147.3
(34.3)
82.0
(21.4)
84.0
(12.4)
113.9
321.2
(11.5)
463.1
AUG 24
(23.1)
(54.2)
362.5
1980
JUN 29
JUL 26
(9.9)
45.6
(25.8)
JUN 1
MAY 2
APR 1
,
57.5
(22.0)
(14.4)
166.9
(22.5)
252.0
SEP 24
(15.7)
47.1
(15.9)
119.6
FEB 12
(17.5)
62.7
(38.1)
292.6
(29.2)
63.8
305.4
(12.4)
1981
APR 6
MAY 3
(39.4)
147.5
353.9
(25.1)
MAY 30
Mean total Zos tera biomass expressed as g dry weight m2 at the three transects during the
period fro m Apr11 1 1980 to May 30, 1981. The values are the means of 5 to 7 observations.
The standa rd error of the mean is in parentheses.*
*Dashes indicate no data available.
TRANSECT
Table 44.
-206-
-207-
contrast, total biomass of transect 2 increased throughout the summer of
The pattern for the increase of total biomass at transect 2 during 1980
1980.
closely followed that for transect 3 until July 26.
Subsequently, total
biomass at transect 3 decreased, while that for transect 2 continued to
increase (Fig. 45).
Field notes taken during April and May described a
sparse, patchy distribution of shoots at transects 2 and 3; evidence of
erosion and burial of shoots were also noted.
An impoundment of water in the
low intertidal region was formed by the large, dense Zostera shoots grawing in
a basin created by sand deposition along the edges of the bed.
termed the Zostera pond (Fig. 37).
This area was
Its boundaries were made obvious during
the lowest tides by the presence of about 15 cm of water, and during high
tides by calm water in the region, caused by the dampening effects of the
leaves.
As the summer progressed and the shoots increased in size throughout
the bed, the boundaries of the Zostera pond increased to include transect 2,
and that transect began to look more like transect 1.
Furthermore, at
transect 3, plants growing in areas where pools formed were in better
condition than plants growing in areas completely exposed at low tide.
When total biomass was compartmentalized into aboveground and belowground
biomass, some new patterns emerged.
Aboveground and belowground biomass at
transect 2 and aboveground biomass at transects 1 and 3 reflected the pattern
described for total biomass, while the pattern for belowground biomass at
transects 1 and 3 was different (Tables 44, 45, and 46).
In 1980, at transect
1, belowground biomass changed relatively little from April 1 to June 29
(Table 46).
A maximum belowground biomass of 206.9 g dry weight m2 was
recorded a month later on July 26.
Belowground biomass decreased during late
E
1980
DATE
SEP24
AUG24
JUL26
JUN29
JUN1
1981
MAY3
FEB12 APRG
TOTAL ZOSTERA BIOMASS
MAY30
2(+1.2m)
3(+1.4m)
I (+1.lm)
Zos tera biomass at three transects in Netarts Bay during the period from April 1, 1980
1.
Each point represents the mean of 5 to 7 observations.
y 30, 198
MAY2
APR1
Total
to Ma
200
300
Figure 45.
a
0
w
N
500
-209-
summer and fall, and increased again between February 12 and April 6, 1981.
In contrast to the rapid accumulation of total and aboveground biomass
observed at transect 1 in the spring of 1981, belowground biomass did not
reach a level comparable to that of spring 1980 until May 3, 1981.
At
transect 3 there was a small peak in belowground biomass in April during both
1980 and 1981, followed by a larger peak that occurred with the maximum
aboveground biomass (Tables 45 and 46).
during late summer, fall and winter.
In 1980, belowground biomass declined
Therefore, an increase in belowground
biomass during April 1981 preceded the increase in aboveground biomass at
transect 3.
There was a striking difference between aboveground biomass at transects
1 and 3 during 1980 and 1981 (Table 45).
At transect 1, the aboveground
biomass for May 30, 1981 was 25% higher than that recorded on June 1, 1980.
At transect 3, the aboveground biomass on May 30, 1981 was 48% higher than the
maximum aboveground biomass reached in 1980.
In general, at all three transects belowground biomass was a more conservative factor than aboveground biomass.
The percentage increase of above-
ground biomass was compared to that for the belowground biomass for the period
from April 1 to September 24, 1980 (Table 47).
The percentage increase of
aboveground biomass ranged from 161% at transect 1 to 714% at transect 3.
The
percentage increase of belowground biomass ranged from 55% at transect 1 to
185% at transect 2.
Therefore, the percentage increase of aboveground biomass
was much higher than the percentage increase of belowground biomass at all
transects.
(10.8)
22.0
(8.3)
34.9
(7.3)
(8.7)
(4.1)
70.4
(7.8)
53.5
57.1
30.3
8.1
(2.6)
7.2
(1.0)
(7.9)
(13.0)
(7.7)
22.3
-
57.6
119.4
173.9
(7.6)
FEB 12
SEP 24
49.5
(19.9)
(9.3)
71.0
(10.0)
256.2
(21.1)
AUG 24
(21.6)
60.8
37.8
26.6
(3.1)
11.3
(2.7)
(37.0)
197.8
(21.4)
162.1
114.8
(5.4)
1980
JUL 26
JUN 29
JUN 1
MAY 2
(10.9)
98.7
APR 1
Dashes indicate no data available.
TRANSECT
(8.4)
21.6
-
(21.6)
166.5
32.4
(14.1)
(5.1)
181.0
1981
MAY 3
APR 6
(23.5)
84.4
202.4
(16.6)
MAY 30
Table 45. Mean abovegroun d Zostera bioinass expressed as g dry weight m2 at the three transects during
the period from April 1, 1980 to May 30, 1981. The values are the means of 5 to 7 observations.
The standard er ror of the mean is in parentheses.*
-2 10-
JUN 1
151.7
(14.1)
44.2
(12.6)
35.1
(5.2)
HAY 2
154.1
(14.5)
58.5
(1.0)
37.3
(9.8)
APR 1
160.8
(15.2)
34.3
(7.4)
71.7
(10.4)
Dashes indicate no data available.
TRANSECT
(17.6)
54.1
(16.0)
53.1
(18.9)
164.4
85.6
(22.3)
76.3
(15.5)
206.9
(11.7)
1980
JUN 29
JUL 26
(12.5)
53.7
74.5
(14.3)
(5.0)
147.2
AUG 24
35.5
(14.3)
(8.1)
96.6
(14.6)
132.5
SEP 24
(8.3)
24.8
-
(8.2)
62.0
FEB12
(12.1)
41.1
-
(18.5)
126,1
31.4
(15.3)
(7.8)
124.4
1981
MAY3
APR 6
(16.6)
63.2
(12.1)
151.6
MAY30
Table 46. Mean belowgroun d Zostera biomass expressed as g dry weight m2 at the three transects during
the period from April 1, 1980 to May 30, 1981. The values are the means of 5 to 7 observations.
The standard er ror of the mean is in parentheses.*
-211-
Transect
Table 47.
143
50
35-85
714
50
7-57
185
63
34-97
546
60
11-71
55
73
133-206
Range
161
158
98-256
Range
Belowground Biomass
% Increase
Difference
aboveground and belowground biomass along transects
Biomass
period from April 1 to September 24, 1980.
2
The
percentages
were
calculated
from
weight m
of 5 to 7 observations.
Aboveground Blomass
% Increase
Difference
Percentage increase of
1, 2, and 3 during the
was expressed as g dry
the ratio of the means
-2 13-
Comparing aboveground and belowground biomass as a proportion of total
biomass gave additional insights into seasonal trends.
At all transects,
belowground bioinass comprised the greater proportion of the total biomass at
the beginning and end of the sampling period in 1980 (Table 48).
At transect
1, both aboveground and belowground biomass accounted for between 40 and 60%
of the total biomass over the entire sampling period, each fraction averaging
approximately 50%.
In contrast, belowground biomass at transects 2 and 3
always comprised more than 50% of the total biomass in 1980, and April 1980 it
represented 90% of the total biomass at transect 3 (Table 48).
Changes in total biomass were the result of changes in shoot density and
leaf or plant size along the transects.
Leaf size was monitored as the change
in the average area of a leaf from a vegetative shoot.
Mean plant size was
calculated by dividing total Zostera biomass by mean shoot density.
Multiple
regression analysis of the relationship between total biomass and plant size
and density, and between total biomass, and leaf size and density indicated
that there was a linear relationship between the dependent and independent
variables (Table 49).
Plant size and density were better predictors of total
biomass than were leaf size and density.
This was understandable because
plant size included both aboveground and belowground portions of the plant,
while leaf size represented only the aboveground parts.
These relationships
can be used to obtain an estimate of total biomass through a combination of
field counts of density and an estimate of leaf or plant size rather than by
harvesting and sorting material from quadrats.
Average leaf size expressed as cm2 increased from April 1 to August 24,
1980 at all transects (Fig. 46, Table 50).
The relatively small leaf size
measured on September 24, 1980 reflected the completion of the sloughing of
78.4
90.1
Belowground
53.2
Dashes indicate no data available.
21.6
9.9
Aboveground
46.8
50.4
68.3
73.9
Belowground
TRANSECT 3
49.6
31.7
26.1
Aboveground
58.1
37.5
62.6
58.3
55.9
58.0
41.7
57.7
42.0
52.7
45.9
40.9
47.3
SEP 24
54.1
AUG 24
44.1
49.9
50.4
41.9
50.1
49.7
44.9
46.3
50.4
56.5
62.1
Belowground
TRANSECT 2
55.1
JUL 26
53.3
1980
JUN 29
49.6
JUN 1
43.5
MAY 2
37.9
APR 1
34.4
65.6
52.5
43.1
51.8
47.2
56.9
57.2
42.8
49.2
42.8
40.7
50.8
57.2
MAY 30
59.3
1981
MAY 3
APR 6
48.2
FEB 12
Percentage of total blomass corresponding to aboveground and belowground material at the three
The percentages were calculated
transects for the period from April 1, 1980 to May 30, 1981.
from the ratio of the means of 5 to 7 observations.*
Aboveground
TRANSECT 1
Table 48.
-214-
-215-
Table 49.
TRANSECT
Multiple regression of mean total Zostera biomass
(TZOS) against mean leaf size (AREA), mean plant
size (SIZE), and mean shoot density (TSHD) for each
transect. R2 is the coefficient of determination.
MODEL
R2
0.66
TZOS
18.54 + 6.73 AREA + 0.07 TSHD
0.80
TZOS
-101.41 - 1.29 SIZE + 1.22 TSHD
0.86
TZ?DS
69.74 + 7.36 AREA - 0.03 TSHD
0.98
TZOS
78.04 + 1.08 SIZE + 0.07 TSHD
0.84
TZOS
-27.37 + 0.53 AREA + 5.00 TSHD
0.98
TZOS
-97.63 + 0.01 SIZE + 1.05 TSHD
Figure 46.
0
20
JUL26 SEP24 FEB12
JUN 29 AUG 24
1980
DATE
JUN1
MAY 2
APRI
3
MAY30
(1.4m)
(+1.2m)
(i-1.lm)
Mean leaf size as expressed by the average area of a leaf from a vegetative shoot, considering
both sides, along the three transects in Netarts Bay.
Each point represents the mean of 5 to
7 observations.
a:
Lii
3O
40
TRANSECT
TRANSECT
TRANSECT
LEAF SIZE
-2 17-
TRANSECT
5.8
(1.3)
12.0
(1.7)
7.6
(1.3)
15.1
(1.8)
37.2
(1.6)
12.0
(4.6)
36.7
1980
JUN 29
JUL 26
Dahses indicate no data available.
(0.4)
2.5
(0.3)
1.8
(0.3)
(1.7)
12.3
6.0
(0.6)
(1.8)
(0.4)
4.6
(0.2)
15.0
4.8
JUN 1
2.5
(0.2)
MAY 2
APR 1
(2.9)
12.1
(2.0)
18.6
(4.0)
42.1
AUG 24
(2.1)
10.6
(3.8)
16.4
(2.4)
30.3
(0.3)
2.3
-
3.0
(0.11)
FEB 12
(0.6)
3.3
-
5.5
(0.5)
APR 6
1981
5.7
(0.2)
-
(0.6)
8.0
MAY 3
7.2
(0.7)
-
(1.8)
14.5
MAY 30
Table 50. Mean leaf size measured as the average area of a leaf from a vegetative shoot and expressed as
cm2 for the three transects for the period from April 1, 1980 to May 30, 1981. The values
represent the means of 5 to 7 observations. The standard error of the mean is in parentheses.
N
I
-2 18-
the large leaves produced during the sampling period in 1980 and the beginning
of the change to the small, narrow leaves typical in the winter.
In the
spring of 1981, at transect 1, leaf size increased at a lower rate than it did
Mean leaf size on Nay 30, 1981 was similar to that for
in the spring of 1980.
May 2, 1980 (Table 50).
In contrast at transect 3, mean leaf size increased
at a higher rate in the spring of 1981 than it did in the spring of 1980.
Mean leaf size on May 30, 1981 was similar to that for June 29, 1980 (Table
50).
The changes in plant size were similar in pattern to changes in total
biomass at all transects during the sampling period in 1980 (Fig. 45 and
47).
En the spring of 1981 at transects 1 and 3, plant size increased at a
lower rate than in the spring of 1980.
At transect 1, the mean plant size on
May 3, 1981 was similar to that measured on April 1, 1980, and at transect 3
the mean plant size for April through June 1, 1980 was not reached until May
30, 1981 (Table 51).
Differences between the leaf and plant sizes measured in 1980 and those
measured in 1981 can be explained in conjunction with the changes in shoot
density.
At transects 2 and 3, during the sampling period in 1980, shoot
density, plant size, leaf size and total biomass follow the same general
patterns of change (Fig. 45, 46, 47 and 48).
At transect 1, during the same
period, shoot density decreased as plant size and leaf size increased.
Total
bioniass was greater in transect 1 than at transects 2 and 3 in April 1980
because the shoot density at transect 1 was three times greater than that at
transects 2 and 3 (Fig. 45 and 48) when plant size was similar at all three
transects (Fig. 47).
Although shoot density decreased from April through
Figure 47.
0
10101
200
JUN1
1980
DATE
1981
MAY30
MAY3
JUL26 SEP24 FEB12 APR6
MAY2 JUN29 AUG24
APR1
1(-H.lm)
RANSECT 2(l.2m)
RIANSECT
.1 RIANSECT 3(+1.4m)
PLANT SIZE
Mean size (mg) of a vegetative plant along the three transects in Netarts Bay during the
Each point represents the mean of 5 to 7
period from April 1, 1980 to May 30, 1981.
observations.
-J
J
Cl)
300
rr.i
104.4
101.1
88.2
70.7
84.7
58.7
81.7
1
2
Dashes indicate no data available.
81.4
105.2
119.4
160.9
127.0
88.7
TRANSECT
330.8
194.9
JUN 1
MAY 2
1980
JUN 29
JUL 26
66.8
253.3
152.4
115.0
313.4
68.8
90.0
42.0
FEB 12
SEP 24
AUG 24
54.5
76.1
70.1
88.7
1981
MAY 3
APR 6
Mean size of a vegetative plant expressed as milligrams at the three transects for the
period from April 1, 1980 to May 30, 1981. The percentages were calculated from the
ratio of the means of 5 to 7 observations.
APR 1
Table 51.
-2 20-
88.8
104.2
MAY 30
- - -
Figure 48.
0
[I$IIS]
I
I
JUNI
I
I
I
I
I
I
I
I
I
I
1980
DATE
1981
V
JUL26 SEP24 FEB
12 APR6 MAY30
MAY2 JUN29 AUG24
MAY 3
APR1
TRANSECT 1(+lim)
TRANSECT 2(+1.2m
TRANSECT 3(i-1.4m
SHOOT DENSITY
- - -
Mean shoot density (shoots m2) along the three transects in Netarts Bay during the period
from April 1, 1980 to May 30, 1981. Each point represents the mean of 5 to 7 observations.
(I)
0
0
F- 2000
(I)
3000
i.IiI.
-222-
September at transect 1, total biomass continued to increase in response to
the increase in leaf and plant size until July 26 (Fig. 45, 46, 47 and 48).
Therefore, the data indicated that shoot density was independent of plant size
until some threshold was reached, above which plant size has a negative effect
on density.
Mean leaf area per unit area of substrate expressed as m2 m2 measured
the combined effects of shoot density and plant size.
were considered in this measurement.
Both sides of the leaf
When plant size and density combined to
produce a mean leaf area per unit of substrate of between 7.5 and 11 m m2,
shoot density began to decrease at transect
1
(Tables 52 and 53).
and 3 never reached this mean leaf area per unit area of substrate.
Transects 2
This
response was probably the result of self-shading within the Zostera bed in the
region of transect 1.
In addition, plant sizes were relatively large in the
samples taken on June 29 and July 26, 1980 at transect 1.
This suggested that
there had been a selective loss of small shoots prior to that time, possibly
due to shading from the large shoots.
Data from all transects for 1980 and 1981 were pooled to examine the
properties of the entire Zostera bed.
interest were listed in Table 54.
Sample statistics in the variables of
Relationships that existed for each tran-
sect were still evident when the data were pooled (Table 55).
Aboveground and
belowground biomass were highly correlated with each other and with total biomass.
Total shoot density and the average area of a vegetative leaf were less
highly correlated with total biomass.
However, since they represented compon-
ents of biomass, i.e., number of shoots and size of aboveground parts, when
they were combined in a multiple regression against total Zostera biomass they
1368
(140)
1025
(308)
804
(111)
536
(140)
782
(148)
(295)
(236)
(212)
(134)
(148)
1400
(156)
1400
929
1188
789
(253)
Jul 26
954
(97)
1860
2000
2125
(176)
2925
(293)
1980
JUN 29
JUN 1
MAY 2
APR 1
(185)
500
(359)
1135
(436)
1150
(428)
910
(120)
(162)
896
(228)
-
-
1095
886
3445
)
(143)
3845
L'Utl
(387)
1790
1981
AITh U
LtL
J1D IL
(136)
995
SEP 24
(87)
(160)
1025
AUG 24
J'J
(387)
1761
-
(359)
3395
A1
IiLtl
Mean shoot density expressed as shoots m2 at the three transects during the period from
April 1, 1980 to May 30, 1981. Values represent the means of 5 to 7 observations. Standard
error of the mean is in parentheses.
Dashes Indicate no data available.
TRANSECT
Table 52.
-2 23-
-224-
TRANSECT
1.7
(0.2)
Dashes indicate no data available.
0.5
(0.2)
0.3
(0.1)
4.6
(0.6)
3.0
(1.3)
5.4
(0.9)
2.4
(0.6)
1.8
(0.3)
0.6
(0.1)
15.7
(1.9)
4.1
(2.4)
(1.1)
14.4
9.1
1980
JUN 29
JUL 26
(1.1)
JUN 1
(1.4)
MAY 2
11.9
4.9
(0.6)
APR 1
(0.1)
2.3
(0.8)
4.1
(0.9)
11.1
AUG 24
1.5
(0.6)
(0.6)
4.6
7.5
(0.8)
SEP 24
(0.3)
0.9
(0.1)
1.8
FEB 12
(0.5)
1.4
7.5
(1.3)
2.4
(0.9)
(0.4)
11.0
1981
APR 6
MAY 3
(1.5)
6.0
(1.2)
15.9
MAY 30
Table 53. Mean leaf area per unit area of substrate expressed as m2 m2 at the three transects during
the period from April 1, 1980 to May 30, 1981. Values represent the means of 5 to 7 observations.
Standard error of the mean is In parentheses.*
I-,
-225-
Table 54.
Sample statistics for Zostera biomass and selected
morphometric data corresponding to the entire
Zostera bed over the whole sampling period from
April 1 to September 24, 1980 and from February
12 to May 30, 1981 (n = 175).
Mean
Standard
Error
Range
Total Biomass2
(g
dry wt. m
)
165.3
9.5
0-554
79.2
5.5
0-326
86.0
4.4
0-240
1454.1
75.9
11.5
0.8
Aboveground Bomass
(g dry wt. m
)
Belowground Bi9mass
(g dry wt. m )
Shoot Density
(shoots m2)
Average Area of
Vegetative Leaf* Lcm2)
Both sides considered.
0-4950
0-57
-2 26-
Table 55.
A matrix of correlation coefficients relating
Zostera biomass and selected morphometric variables
for the pooled data set, i.e., all samples from the
TZOS = total Zostera biomass;
three transects.
ABGB = aboveground biomass; BLGB = belowground
biomass; TSHD = total shoot density; AREA = average
area of a vegetative leaf, both sides considered.
Values greater than 0.2 are significantly different
than zero where P < 0.01.
TZOS
ABGB
BLGB
TSHD
AREA
TZOS
ABGB
BLGB
TSHD
AREA
1.00
0.97
0.95
0.67
0.64
1.00
0.84
0.65
0.65
1.00
0.63
0.56
1.00
0.03
1.00
-227-
accounted for a large proportion of the variance in total biomass (Table
Again, this supported the idea presented earlier that measurement of
56).
shoot density and the average area of a vegetative leaf can be used to obtain
an estimate of total Zostera biomass.
Primary Production
Shoot net primary production (g dry weight m2 sample period), as
measured by the leaf marking method, had a similar pattern at all transects
throughout the study (Fig. 49, Table 57).
During the period from June 14 to
October 23, 1980, there were two peaks in net primary production of the
shoot.
The first occurred between June 29 and July 26 and was reflected by
peaks in total biomass at transects 1 and 3 (Fig. 45).
A second and smaller peak in net primary production of the shoot occurred
between August 24 and September 24.
This maximum was not reflected in the
measurements of total bioinass at transect 1 and 3 for the same period because
of a decrease in shoot density and plant size that occurred at the same time
(Fig. 47 and 48).
Total biomass at transect 2 increased throughout the
sampling period in 1980.
The decrease in net primary production of the shoot
at all transects between July 13 and August 24 was concurrent with a bloom of
Enteromorpha prolifera in the area (see Davis, 1982).
As the Enteromorpha
drifted through the Zostera bed with the incoming or outgoing tide, the long
leaves of the seagrass became tangled in the ropes of the alga, and the
Zostera was uprooted as it was dragged along.
In areas where Enteromorpha had
become caught in the sediment or on some object, the Zostera in the vicinity
became buried from an increase in the sedimentation caused by the slowing of
-I
-2 28-
Table 56.
Multiple regression of total Zostera biomass (TZOS)
against total shoot density (TSHD) and the average
area of a vegetative leaf (AREA) for the entire
Zostera bed.
R2 is the coefficient of determination.
MODEL
0.40
TZOS = 43.2 + 0.08 TSHD
0.40
TZOS = 81.8 + 7.3 AREA
0.83
TZbS = -36.0 + 0.06 TSHD + 4.2 AREA
0
1980
DATE
JUNI JUL26
SEP24
JUN29
AUG24
OCT23
TRANSECT2(+I.2m)
TRANSECT3(1.4m)
'TRANSECT 1 (il.lm)
SHOOT
1981
MAY3
JUL1
APR6 tAY3O
Shoot net primary production expressed as g dry weight m2 along three transects for the
period from June 1980 to July 1981, Each point represents the mean of 14 or 15 observations.
0
Figure 49.
0
clOO
0
>-
w
I
E
(\J
N
0
3
Transect
NPP-PER
NPP-DAY
Transect
22.5
1.6
108.9
9.1
APR 6APR 18
Based on data from two shoots.
3
NPP-PER
NPP-DAY
Transect 1
Sampling Period
1981
36.0
2.6
47.6
3.2
NPP-PER
NPP-DAY
2
Transect
NPP-PER
NPP-DAY
129.1
8.6
NPP-PER
NPP-DAY
Transect 1
JUN 14JUN 29
30.0
2.1
7.6
113.8
APR 18MAY 3
39.5
2.5
66.0
4.4
153.4
10.2
JUN 29JUL 13
39.6
2.8
122.2
9.4
MAY 3NAY 16
48.7
3.7
57.1
4.8
81.1
6.2
JUL 13JUL 26
65.1
4.7
150.0
10.7
MAY 16MAY 30
36.3
2.3
32.0
2.0
69.3
4.3
JUL 26AUG 12
2.5
42.1
230.5
13.6
MAY 30JUN 17
13.5
1.0
31.7
2.6
41.7
3.5
AUG 12AUG 24
37.2
2.7
114.2
8.2
JUN 17
JUL 1
35.3
2.2
53.8
3.4
AUG 24SEP 8
*
1.9k
0.1
43.4
2.7
68.7
4.3
SEP 8SEP 24
27.1
1.9
31.0
2.2
61.4
4.4
SEP 24OCT 7
14.8
0.9
20.2
1.3
44.4
2.8
OCT 7OCT 23
Shoot net primary production along the three transects during the period from June 14, 1980 to
July 1, 1981. NPP-PER = shoot net primary production expressed as g dry weight m2 sample
period1; NPP-DAY = shoot net primary production expressed as g dry weight nr2 dayl. The
values represent the means of 14 or 15 observatIons.
Sampling Period
1980
Table 57.
-2 30-
-231
the water by the tangled mass of the Enteromorpha.
Eventually even the
Enteromorpha was buried, and an oozing, sulfurous mound of sediment marked the
place where there had been a patch of Zostera.
The disappearance of
Enteromorpha from the Zostera bed in early August was followed by an increase
in net primary production of the Zostera shoots (Fig. 49).
The rate of shoot net primary production was greater in 1981 than in 1980
(Fig. 49).
The maximum rate of shoot net primary production was reached in
early June in 1981 as compared to early July in 1980.
At transect 1, the
maximum rate of shoot net primary production in 1981 was 50% higher than that
of 1980, while that for transect 3 was 21% higher (Table 57).
At transect 1, the accumulation of total biomass was divided into five
phases.
Between February 12 and April 6, 1981, there was a large increase in
total Zostera biomass that was the result of a large increase in shoot density
(Fig. 45 and 48).
During the same period of time, mean leaf size increased
slightly from 3.0 cni2 to 5.5 cm2.
from 66.8 mg to 76.1 mg.
Mean plant size also increased slightly
A similar pattern was noted in 1980.
Presample data
from February 23, 1980 gave a mean density of 1387.5 shoots m2 with a
standard error of 143.9 shoots m2.
Subsequently, density increased to 2925
shoots m2 by April 1, 1980 (Table 52).
Therefore, primary production in the
early spring at transect 1 was first channeled into the production of new
shoots.
Then the change in leaf morphology from small, narrow leaves typical
in the winter to long, wide leaves typical in the summer occurred during April
and May 1981.
It was only after this change was completed that the sharp
increase in shoot net primary production was initiated during the month of May
1981, thereby making a shift in growth strategy to the production of above-
-2 32-
ground parts.
The sharp decrease in net primary production of shoots observed
at transects 1 and 3 during June 1981, coincided with a bloom of Enteromorpha,
just as the decrease in net primary production of shoots during July and
August 1980 coincided with a similar bloom.
Therefore, the same pattern of
growth was followed during both 1980 and 1981.
The stages involved in this
general pattern are summarized in Figure 50.
Conditions for the growth of Zostera were better at transect 1 than at
transects 2 and 3.
Maximum mean total biomass, mean shoot density, mean leaf
size, mean plant size and mean shoot net primary production at transect 1 were
always greater than at transects 2 and 3 (Table 58).
During the summer low
tides, Zostera growing in the region of transect 1 was never exposed.
Even
during the lowest tides, 10 to 15 cm of water remained in the Zostera pond.
This layer of water protected the plants from exposure to the air.
This
conclusion was further supported by the relatively high shoot density and
relatively large shoots observed in areas with pooled water during low tide at
transect 3.
In the winter, there was a noticeable difference in the density
and condition of plants located above and below the level of the higher low
tide.
Transect 1 was located below this elevation, while transects 2 and 3
were located above it.
Shoots in the region below the average height of the
winter higher low tide appeared to be protected.
These shoots were exposed to
the air during low tide and no more than once a day during the winter, while
the rest of the Zostera bed was exposed twice each day.
The edges of the bed
showed evidence of erosion, and plants in this area often had their rhizomes
exposed as the sand around them was washed away.
During the entire year there
was evidence of sand deposition in the high intertidal region, especially
-233-
DECEMBER TO
FEBRUARY
MARCH
APRIL a MAY
LATE MAY
THROUGH AUGUST
SEPTEMBER
THROUGH NOVEMBER
Figure 50.
WINTER GROWTH FORM
(SHORT, NARROW LEAVES)
INCREASE IN SHOOT DENSITY
CONVERSION TO SUMMER
GROWTH FORM
LONG, 'NIDE LEAVES)
HIGH RATE OF GROWTH OF
ABOVEGROUND PARTS
CONVERSION TO WINTER
GROWTH FORM
(SHORT, NARROW LEAVES)
The annual phases of growth exhibited by Zostera
marina L. growing along transect 1 in Netarts Bay,
Oregon.
148
Transect
3
354
Transect 1
1981
3
Transect
143
186
2
Transect
Total Biomass
(g dry wt. nr2)
7.2
3845
1661
88.8
1368
115.0
12.1
104.2
1400
152.4
18.6
14.5
2925
(shoots m2)
Shoot Density
313.4
(mg)
Shoot Size
42.1
(cm2)
Leaf Size
Maximum mean values of total biomass, leaf size, shoot size, and shoot
density along the transects in 1980 and 1981.
463
i8.
Transect 1
1980
Table
-234-
-235-
along transect 3.
Neither erosion nor sedimentation was as evident in the
region of the bed where transect 1 was located.
Therefore, a combination of
factors apparently contributed to the differences between plants that grew in
the region of transect 1 and those located in the region of transects 2 and 3.
IV.
Relationship Between Zostera and Epiphytic Assemblages
Description of Epiphytic Assemblages
Epiphytic assemblages on Zostera in Netarts Bay were primarily composed
of diatoms.
Epiphyte biomass expressed as ash-free dry weight m2 from pooled
data representing the entire Zostera bed had a high correlation with biomass
expressed as dry weight.
The mean ratio of ash-free dry weight to dry weight
was 0.24, which is a typical value when the flora consists of diatoms
(Mclntire and Phinney, 1965).
The ratio of ash-free dry weight to dry weight
for each transect also indicated a diatom flora, except for the samples in
1980 taken on June 1 and 29 (Fig. 51).
By inspection under a microscope it
was noted that during this time of the year Smithora naiadum (Anderson)
Hollenb. and Ectocarpus sp., or other non-diatom algae were prominent
components of the epiphyte community.
The addition of these taxa increased
the organic matter content of the epiphytic assemblage, as the percentage ashfree dry weight for most algae other than diatoms is usually greater than 60%
(e.g., see Davis, 1982).
The percentage ash-free dry weight for samples
obtained in February and April, 1981 also was high.
During this period, the
combination of a small biomass of epiphytes and unusually brittle Zostera
leaves created a problem of contamination of the epiphytic samples with
particles of Zostera leaves.
Figure 51.
0
LU
APR1
MAY2 JUN1
JUN29 JUL26 AUG24 SEP24
DATE
T
RANSECT 2(+l.2m)
RANSECT 3(+1.4m)
uT RANSECT 1 (-'-I.lm)
Perc entage ash-free dry weight associated with the biomass of epiphytes at the three
tran
sects during the period from April through September 1980. Each point represents
the mean of 3 subsamples.
20
30
z
LU
0 40
I-
w60
(9
0
1L70
80
EPIPHYTE % AFDW
-2 37-
The taxonomic structure of the diatom assemblages epiphytic on Zostera
marina L. in Netarts Bay is described by
to 170 of this report.
Whiting (1983) and on pages 137
From November through July, the flora was dominated by
species of Cocconeis, Synedra, Navicula, Nitzschia, Gomphonema and Rhoicosphenia.
From August through October, Cocconeis, Gomphonema and Rhoicosphenia
virtually disappeared from the samples, and different species of Navicula and
Nitzschia became the dominant taxa.
The Shannon-Weaver diversity index
revealed that the epiphytic flora was generally low in species richness and
high in dominance.
B ioma s s
The interpretation of changes in epiphyte loads was related to the units
that were used to express biomass.
Epiphyte biomass expressed as g dry weight
m2 also included inorganic material, e.g., debris and dead diatom frustules.
Therefore, dry weight expressed the actual load of material that was distributed over the leaves.
Biomass expressed as ash-free dry weight m2 was
considered an indicator of the organic matter present.
Epiphytes were prominent on the Zostera leaves from April through
October.
During the winters of 1979 and 1980, field notes indicated that the
Zostera leaves were essentially free from epiphytes.
This conclusion was
supported by biomass measurements taken on February 12, 1980, when epiphyte
biomass for transects 1 and 3 were 0.4 and 0.7 g dry weight m2, respectively.
During the sampling period from April through September 1980, epiphyte biomass
expressed as dry weight was the greatest at transect 1.
There was little net
increase or decrease in epiphyte hioniass at the transects from May through
September 1980 (Fig. 52, Table 59).
Figure 52.
0
20
4O
JUN1
JUL26 SEP24
MAY2
JUN29 AUG24
1980
DATE
APRI
-2
1981
APR6
MAY30
FEB12 MAY3
TRANSECT 1 (-t-1.lm
TRANSECT 2 (+ 1.2m
TRANSECT 3 (+1.4m
EPIPHYTE BIOMASS
Epiphyte biomass expressed in g dry weight m
for all three transects over the period
from April 1980 through May 1981., Each point represents the mean of 5 to 7 observations.
0::
a
>-
60
100
TRANSECT
(4.6)
(3.3)
5.1
10.0
8.0
(3.6)
Dashes indicate no data available.
C'1
1.5
(0.5)
(2.3)
(25.2)
81.4
(3.9)
11.0
(6.1)
24.7
80.7
(22.3)
1980
JUN 29
JUL 26
(9.0)
(3.3)
10.1
23.4
(5.7)
JUN 1
5.5
(2.4)
29.3
72.1
(11.0)
MAY 2
8.4
(7.1)
66.1
APR 1
5.1
(1.4)
8.8
(2.7)
(11.4)
44.1
AUG 24
6.7
(2.9)
(3.7)
24.1
(12.6)
87.0
SEP 24
(0.2)
0.7
(0.1)
0.4
FEB 12
(0.3)
0.7
(3.0)
16.0
(0.9)
8.6
(2.1)
(6.5)
1.8
34.3
(9.2)
MAY 30
Standard
65.0
1981
MAY 3
APR 6
Values are the means of 5 to 7 observations.
-239-
Table 59. Mean epiphyte blomass (g dry wt. m2).
error of the mean is in parentheses.
N-I
-2 40-
The principal difference between the pattern in epiphyte biomass
expressed as g dry weight m2 and that expressed a g ash-free dry weight m2
was an obvious increase in organic matter relative to dry weight biomass at
transect 1 in June and July 1980 (Fig. 53, Table 60).
This was the result of
the increase in percentage ash-free dry weight that occurred when the flora
changed from exclusively diatoms to an assemblage that included Smithora and
Ectocarpus.
Therefore, biomass as ash-free dry weight reflected shifts in the
composition of the flora that were not evident from biomass data expressed as
dry weight.
Epiphyte biomass was significantly correlated (r > 0.6, P < 0.01) with
Zostera aboveground, belowground and total biomass, and with the average area
of a vegetative leaf and shoot density (Table 61).
However, epiphyte biomass
was not correlated with the number of leaves per shoot (P > 0.01).
Changes in
number of leaves per shoot occurred independent of changes in Zostera biomass,
and of changes in leaf area and shoot density which were closely related to
changes in the growth rate of the host plant.
Therefore, the data Indicated
that the pattern in the epiphyte biomass was closely related to the accumulation of Zostera biomass.
Epiphyte load was examined by expressing epiphyte biomass as g dry weight
per g dry weight of Zostera leaf.
Epiphyte loads were highest in April and
May 1980; a maximum value of 2.3 g epiphytes/g leaf was measured at transect
2 in May (Fig. 54).
From June 1 through September 1980, the loads averaged
0.4 g epiphytes per g leaf with a standard error of 0.06 g epiphytes per g
leaf.
Therefore, during the period of time when Zostera biomass was highest,
the epiphyte loads were the lowest, because of an increase in Zostera biomass
during a time when there was no net increase in epiphyte biomass.
Figure 53.
0
20
I
I
I
I
1980
DATE
JUN1
JUL26 SEP24
2
JUN
29
AUG 24
MAY
APRI
-
EPIPH Y TE
Epiphyte bi omass expressed as g ash-free dry
during the period from April 1980 to May 30, 1981.
to 7 observ ations.
(I)
r
LL
a:
w
w
>-.
F-
E
25
30
1981
MAY3
i-f
APR6
I
MAY 30
at t hree trans ects in Netarts Bay
Each poi nt represents the mean of 5
m
-2
FEB12
TRANSECu (tl.lm)
TRANSECT2 (+1.2m)
TRANSECT3(+1.4m)
AFDW
2.7
(1.2)
2.3
(1.5)
4.0
(0.9)
2.4
(1.1)
4.0
(1.2)
1.2
(0.5)
0.3
(0.1)
27.5
(8.5)
1.5
(2.0)
(1.5)
2.6
(0.9)
(1.4)
5.7
21.5
(5.9)
1980
JUL 26
JUN 29
(0.6)
9.6
(2.4)
13.6
13.8
JUN 1
MAY 2
APR 1
-
(2.5)
6.6
(1.0)
1.6
(0.7)
2.3
(0.7)
1.3
(0.4)
0.4
(0.1)
0.2
(0.0)
17.3
12.4
FEB 12
(3.2)
SEP 24
AUG 24
(0.1)
0.3
-
(0.9)
5.0
(0.3)
0.6
-
(2.2)
15.5
1981
APR 6
MAY 3
2.3
(0.6)
(1.5)
8.0
MAY 30
Mean epiphyte biomass expressed in g ash-free dry wt. m2. Values are the means of 5 to 7
observations. Standard error of the mean is in parentheses.*
Dashes indicate no data available.
TRANSECT
Table 60.
-242-
-243-
Table 61.
Correlation between epiphyte biomass and total
shoot density (TSHD), average number of leaves
per shoot (LVES), average area of a vegetative
leaf (AREA), aboveground biomass (ABGB), belowground biomass (BLGB), and total Zostera biomass
(TZOS). Epiphyte biomass is expressed as dry
weight (EPDW) and ash-free dry weight (EPAF).
Values greater than 0.2 are significantly
different than zero where P < 0.01.
VARIABLE
EPDW
EPAF
TSHD
0.39
0.38
LVES
0.01
-0.01
AREA
0.57
0.63
ABGB
0.67
0.74
BLGB
0.70
0.72
TZOS
0.71
0.76
Figure 54.
J
[$1
1.5
2.0
I
I
1980
I
I
I
JUN1
DATE
1981
I
TR ANSECT 1 (+1.lm)
TR ANSECT 2(+1.2m)
TR ANSECT 3(+1.4m)
JUL26 SEP24 FEB12 MAY3
MAY2 JUN29 AUG24
APR6 MAY30
APRI
A
EPIPHYTE LOAD
I
Epiphyte load expressed as g dry weight of epiphytes per g dry weight of Zos tera leaf
along three transects for the period from April 1980 through May 1981.
Each point
represents the mean of 5 to 7 observations.
IL
hi
H
>I
C')
Lii
hi
IL
hi
2.5
-245-
Epiphyte biomass was influenced by the regular loss of that portion of
the standing crop which has colonized the oldest Zostera leaf on a shoot.
At
certain times during the study, the loss of a particular group of leaves had
more impact on the epiphyte biomass than the loss of leaves at other times.
The low epiphyte biomasses at transects 1 and 2 on June 1 and August 24, 1980,
and at transect 1 on May 30, 1981, were probably related to the loss of
Zostera leaves that carried a larger proportion of the epiphyte biomass than
was usually associated with the leaves that were sloughed.
The highest loads
of epiphytes in the study were recorded for the sample taken on May 2, 1980
(Fig. 54).
One can predict the time when the leaves present in the Zostera
bed at the time of the samples were sloughed by considering the mean lifetime
of a leaf (34 days), the mean PT (9 days), and the mean number of leaves per
shoot (4) during the time period under consideration (Fig. 55A).
A leaf
initiated by a shoot with four leaves on April 28 would be sloughed 34 days
later on May 31.
The oldest leaf on such a shoot would have initiated growth
three Pr earlier on April 2, and would have been sloughed 34 days later on May
6.
Therefore, most of the leaves present in the Zostera bed on May 2 were
probably sloughed together with their heavy epiphyte load before June 1,
thereby accounting for the decrease in epiphyte biomass measured at that
time.
The loss of epiphyte biomass that occurred between July 26 and August
24, 1980 was explained using the same reasoning.
The leaves that would have
been sloughed during that period were in positions 1 and 2 on the shoot during
the time of maximum shoot production (Fig. 55B).
Leaves in positions 1 and 2
on a shoot together accounted for 75 to 92% of the shoot's growth from July to
October (Table 44).
Therefore, the leaves that were sloughed between July 26
Figure 55.
I
II
I
b
VAYS
30
LEAF GROWTH
HIGHESTRATE OF
1 JULIO
b
BIOM ASS
MAXIMUM
20
30
MEASURED
ZOSTERA
MAXIMUM EPIPHYTE
LOAD MEASURED
j MAYI
d
KEY
2
29
JUN 10
LEAF SLOUGHED
= LEAF /DEN/FIER
LEAF IN/nA rED
LEAF IDENTIFIER
DECREASE IN EPIPHYTE
BIOMASS MEASURED
19
b
(-I
EPIPHYTE
BIOMASS MEASURED
DECREASE
('AUG9
4l
Time line of leaf initiation and sloughing explaining the sharp decreases in epiphyte biomass
observed on June 1 and August 24, 1980. A. The decrease in epiphyte biomass on June 1, 1980
is due to the prior sloughing of the majority of the leaves that carried the highest epiphyte
load of the study.
B. The decrease in epiphyte biomass on August 24, 1980 is due to the loss
of some of the largest leaves produced during the study.
Factors considered included the
plastochrone interval (P1), lifetime of a leaf (LIFE), and number of leaves per shoot (LVES).
JUN 201
MEAN LVES 3
8. MEAN P1 /6 DAYS
MEAN LIFE 46 DAYS
BIOMASS
SAMPLED
APR1
a
MEAN LIFE =34
MEAN LVESX 4
A. MEAN P1= 9OAYS
N)
-247-
and August 24, 1980 were among the largest leaves produced that year.
Since
they were also the oldest leaves on the shoot, they probably carried a large
portion of the epiphyte biomass.
In addition, notes made while sorting the
sample taken in August indicated that many amphipods were present, and that
the Zostera leaves showed signs of herbivory.
Perhaps the process of grazing
also accounted for at least some of the decrease in epiphyte biomass in August
1980.
Production
Measurements of epiphyte primary production using the
method were
made monthly from June to September, when the summer lower low tides were
early in the day.
The results from the 14C measurements were used to
establish a ratio between the rates of 12C assimilation for the Zostera and
the epiphytic assemblage rather than as a direct estimate of epiphyte
production.
It was assumed that Zostera and epiphyte respiratory losses per
unit biomass were the same.
The rates of
accumulation for Zostera and
epiphytes and their ratios are presented in Table 62.
The mean ratio of the
rates of 12C assimilated expressed as mg 12C assimilated (g dry weightY' h
for the epiphytic assemblage and Zostera was 0.60 with a standard error of
0.08.
The ratio was used to estimate the net primary production of the
epiphytes from the net primary production of Zostera obtained with the shoot
marking period.
The net primary production for the epiphytic assemblage was1
calculated for each time interval during which the net primary production of
Zostera was measured.
First, the specific growth rate for Zostera was
80
3
2
Transect
Play 31, 1981
3
2
Transect
August 24, 19
3
2
Transect
85.6
161.9
329.2
702.6
111.0
272.0
146.9
361.2
0.8
0.6
0.7
91.6
22.9
47.6
0.8
36.0
24.8
73.1
19.0
34.0
0.9
111.0
82.3
253.9
71.1
0.4
2.2
1.9
1./s
80.4
18.5
57.1
0.6
0.2
2.8
2.0
1.7
0.4
40.8
1.2
AFDW
0.5
DRY wr
1.8
AFI)W
1.3
DRY WT
Epi phyte ProductIon:
Zostera Product Ion
2.2
AFDW
Zostera Production
0.6
DRY WF
Epiphyte Production
Net primary production of Zostera and the epiphyte assemblage measured using the 11C method along
three transects on .July 2 6 and August 24, 1980, and May 31, 198I. Production is expressed as mg
(I)RY WT) and as mg '2C assimilated (g ash-tree dry wclght
l2
h
assimilated (g dry we lght)
mennso[
2 or 3 replicate saniples.*
Values
11
ste
d are the
(AFDW).
July 26, 1980
Table 62.
-21i8-
-2 49-
calculated by dividing the net primary production of the aboveground portions
of Zostera by the mean aboveground biomass for the period of time under
consideration.
Then the specific growth rate of the epiphyt
was calculated
by multiplying the specific growth rate of Zostera by the mean ratio of the
rates Of '2C assimilation for Zostera and the epiphyce assemblage (0.60).
Finally, net primary production of the epiphytes was calculated by multiplying
the mean biomass of the epiphytes by the specific growth rate of the
epiphytes.
The net primary production
These values are listed in Table 63.
of the epiphyte assemblage at transect 1 ranged from 5.1 to 13.7 g ash-free
dry weight m2 month
(18.7 to 40.5 g dry weight m2 m1) during the period
from June 1980 through June 1981, while that for transect 3 ranged from 0.4 to
2.7 g ash-free dry weight
2
month
(1.1 to 8.1 g dry weight
2
month).
Components of Variance
To gain added insight into the relationships among the morphotnecric and
biornass variables, principal components analysis (PCA) was performed on a
pooled data set for the three transects.
Variables in the data matrix
included shoot density (shoots tn2), number of leaves per vegetative shoot,
mean area of a vegetative 1ef (cm2), aboveground and belowground Zostera
biomass (g dry weight m2), epiphyte biomass (g ash-free dry weight tn2), and
epiphyte load (g dry weight per m2 leaf surface).
Only the first three
components, with eigenvalues greater than or equal to one, were interpretable.
The first three principal components accounted for 82.9% of the variation
in the seven variables (Table 64).
Factor loadings indicated that principal
component 1 (PCi) primarily expresses shoot density, average area of a vege-
-250-
Table 63.
Net primary production of the epiphyte assemblage measured along
the three transects from June 1, 1980 to May 30, 1981.
Production
is expressed as g dry weight m2 (DRY WT) and g ash-free dry weight
in2 (AFDW) for each period of time.*
TRANSECT
AFDW
DRY WT
AFDW
DRY WT
AFDW
JUN 1-JUN 29
36.7
13.7
7.8
3.5
6.8
2.3
JUN 29-JUL 26
40.5
12.2
16.6
6.0
8.1
2.7
JUL 26-AUG 24
18.7
5.1
10.0
2.5
5.6
1.4
AUG 24-SEP 24
29.5
7.1
13.6
3.6
7.0
1.7
APR 6-MAY 3
28.4
7.8
1.1
0.4
MAY 3-MAY 30
39.7
9.4
2.6
0.8
DRY WT
R1Ai]
1981
*Dashes indicate no data available
Variables
0.922
0.856
0.009
3.403
Belowground biomass (g dry wt. m2)
Epiphyte biomass (g ash-free dry wt. m2)
Epiphyte load (g dry wt. m2 leaf area)
Eigen value
48.6
0.953
Aboveground biomass (g dry wt. in2)
Accumulated % of variance
0.704
-0.002
Average area of a vegetative leaf (cm2)
Number of leaves per vegetative shoot
0.644
PCi
67.3
1.305
0.027
0.116
0.070
0.081
-0.570
0.804
0.557
PC2
82.9
1.093
0.976
0.285
0.008
-0.132
-0.017
0.120
-0.162
PC3
Factor loadings corresponding to the first three principal components
(PCI, PC2, PC3) of the morphometric and biomass variables, the
corresponding eigenvlue and accumulated percentage of the variance.
The analyses was based on 175 observations.
Shoot density (shoots m2)
Table 64.
-25 1-
-2 52-
tative leaf, aboveground and belowground Zostera biomass and epiphyte biomass.
These variables all were expressions of the biomass associated with the
Zostera Primary Production subsystem (Fig. 3).
Total biomass for the Zostera
Primary Production subsystem expressed in g ash-free dry weight m2 (ZPP) was
regressed against PCi, generating an R2 value of 0.97; the regression model
was ZPP = 125.87 + 53.03 PCi.
Factor loadings also indicated that the second
principal component (PC2) was an expression of the inverse relationship
between the average area of a vegetative leaf on the one hand and the shoot
density and number of leaves per vegetative shoot on the other hand, i.e., the
morphometrics of a vegetative shoot.
The third principal component (PC3) was
highly correlated with epiphyte load (r = 0.98).
When correlation
coefficients were calculated for this group of variables, epiphyte load was
not correlated with any of the other variables.
In summary, this set of data
generated three independent (orthogonal) components of variance:
autotrophic
biomass, leaf-shoot density (morphometrics), and epiphyte load.
V.
Bioenergetics of the Zostera Primary Production Subsystem
In the Background section of this report, a conceptual model of the Mud-
flat Processes subsystem was presented as a hierarchy of coupled subsystems
(Fig. 3).
This model was used to organize the examination of the bioener-
getics of the seagrass ecosystem in Netarts Bay.
considers several levels of resolution.
The following analysis
At the finest level of resolution,
the Macrophyce Primary Production subsystem is decomposed into aboveground and
belowground Zostera.
The gains and losses of biomass for each of these
components are partitioned and are presented as an energy budget.
The Macro-
-253-
phyte Primary Production subsystem then is integrated with the Epiphyte
Primary Production subsystem to form the Zostera Primary Production
subsystem.
The gain of biomass from the primary production of this subsystem
is expressed as annual net production.
Information accumulated on the growth of Zostera marina L. was
synthesized with respect to the bioenergetics of the Macrophyte Primary
Production subsystem.
The changes in its state variable, the macrophyte
biomass, were examined in terms of the inputs and outputs that affected its
value.
These inputs and outputs were related to the dynamics of the
Macrophyte Primary Production subsystem, as primary production of Zostera was
related to the physiological activities of the plant.
The inputs and outputs
that affect Zostera biomass also represented the couplings between the
Macrophyte Primary Production subsystem and the rest of the subsystems in the
conceptual model.
Consequently, the perspective gained by such an approach
contributed to the understanding of the role that Zostera marina played in the
estuary.
Changes in aboveground biomass were caused by inputs from shoot net
primary production and outputs as lost shoots, sloughed leaves and grazing.
Biomass accumulation due to shoot net primary production and losses due to
sloughed leaves were measured directly and were partitioned separately in the
energy budget.
Shoot net primary production for each sampling period was
calculated according to the following expression:
Shoot net
primary
production
(g dry wt
=
Rate of net
primary production per shoot
(g dry wt per shoot)
x
Mean shoot
density
2
(shoots ni )
-254-
Monthly shoot net primary production, estimated as g dry weight m2, was
calculated by summing the values for the constituent sampling periods.
Losses
due to sloughing of leaves expressed as g dry weight m2 for the time period
under consideration were calculated according to the following expression:
Mean leaf
loss per
in2
Number of
leaves lost
per shoot
Mean number
of shoots
per
tvIeafl dry
weight per
leaf lost
The mean dry weight per leaf of the leaves lost was estimated as the mean
weight of the largest leaf on a shoot at the beginning of the sampling period.
The energy budgets for abovegrourid Zostera are presented in Tables 65, 66
and 67.
The column labeled "difference" represents biomass losses not
accounted for directly in this study, and includes biomass lost as entire
shoots and to grazing.
At all transcts during each time interval under consideration, biomass
losses were at least 50% of the shoot net primary production.
From July
through October 1980, the biomass losses were equal to or higher than the shoot
net primary production.
This indicated the great capacity of the Zostera to
turnover its aboveground biomass.
The lifetime of a leaf ranged from 34 to
55 days during the course of this study.
shoot had an entire set of new leaves.
Therefore, every 34 to 55 days each
With this in mind, it was not sur-
prising that 35 to 100% of the biomass loss was due to sloughed leaves.
The
biomass loss from leaf export occurred in response to the changes in leaf
size.
En April and May the small leaves of the winter growth form were shed,
and leaves exported during this period represented a smaller proportion of
biotnass loss than when the larger summer leaves were lost from June to October.
256.2
173.9
119.4
70.2
57.6
JUL 26, 1980
AUG 24, 1980
SEP 24, 1980
OCT 23, 1980
FEB 12, 1981
202.4
226.0
MAY 30, 1981
JUL 1, 1981
**
**
+23.6
+21.3
+14.5
+108.9
-12.7
-49.2
-54.5
-82.3
+58.3
+35.7
+47.3
+16.1
EBIOMASS
* *
Extrapolated.
Dashes indicate no data available.
181.0
MAY 3, 1981
1%
166.5
1981
6,
197.9
JUN 29, 1980
APR
162.1
JUN 1, 1980
2,
98.7
114.8
MAY
1980
BIOMASS
344.7
272.2
222.7
105.8
122.5
111.0
234.5
220.8
**
NET PRIMARY
PRODUCTION
321.1
250.9
208.2
155.0
177.0
193.3
176.2
185.1
BIOMASS
LOSS
127.2
88.9
89.6
80.6
106.3
98.0
170.3
98.0
LOSS AS
LEAVES
193.9
162.0
118.6
74.4
70.7
95.3
5.3
87.1
DIFFERENCE
Energy budget accounting for the gains and losses of aboveground biomass along transect
1 between April 1, 1980 and July 1, 1981. Values are expressed as g dry weight m2 for
the period of time under consideration.*
1980
1,
APR
DATE
Table 65.
-255-
60.8
71.0
53.5
70.4
60.0
JUN 29, 1980
JUL 26, 1980
AUG 24, 1980
SEP 24, 1980
OCT 23, 1980
-10.4
+16.9
-17.5
+10.2
+23.0
+11.2
+15.3
ABIOMASS
**
Extrapolated.
Dashes indicate no data available.
37.8
JUN 1, 1980
11.3
26.6
2,
MAY
1980
BIOMASS
51.2
78.8
63.7
123.1
85.3
NET PRIMARY
PRODUCTION
61.6
61.9
81.2
112.9
62.3
BIOMASS
LOSS
53.1
49.8
43.3
30.8
17.9
LOSS AS
LEAVES
8.5
12.1
37.9
82.1
44.4
DIFFERENCE
Energy budget accounting for the gains and losses of aboveground biomass along transect
2 between April 1 and October 23, 1980. Values are expressed as g dry weight m2 for
the period of time under consideration. *
1980
1,
APR
DATE
Table 66.
35.0
22.0
22.0
22.3
21.6
AUG 24, 1980
1980
1980
SEP 24,
OCT 23,
FEB 12, 1981
6,
3,
APR
MAY
60.0
JUL 1, 1981
**
-24.4
+52.0
+10.8
-0.7
+0.3
Extrapolated.
0
-13.0
-22.1
+ 7.6
+19.2
+22.2
+0.8
LBI0MASS
Dashes indicate no data available.
84.4
MAY 30, 1981
1981
32.4
57.1
JUL 26, 1980
1981
49.5
1980
JUN 29,
**
30.3
JUN 1, 1980
7.3
8.1
2,
MAY
1980
BIOMASS
79.3
104.7
52.5
-
-
41.8
55.9
49.8
88.2
66.5
-
-
**
103.7
52.7
41.7
-
-
41.8
68.9
71.9
80.6
47.3
-
-
BIOMASS
59.4
19.7
10.6
-
-
14.9
17.4
41.5
27.4
25.2
-
-
**
LOSS AS
44.3
33.0
31.1
-
-
27.2
51.5
30.4
53.2
22.1
-
-
DIFFERENCE
Energy budget accounting for the gains and losses of aboveground biomass along transect
3 between April 1, 1980 and July 1, 1981. Values are expressed as g dry weight m2
for the period of time under consideration.*
1980
1,
APR
DATE
Table 67.
-25 7-
-2 58-
An energy budget also was constructed for belowground Zostera biomass.
The net primary production of belowground Zostera was measured between April
and May 16, 1981, according to the method of Jacobs (1979) and Kenworthy
(personal communication).
The net production of the belowground Zostera
during this period of time was 219.8 g dry weight m2 at transect 1 and 45.3
dry weight m2 at transect 3.
Since a direct measurement of belowground net
primary production was made for only a short time period during this study, an
alternative method of estimating belowground net primary production was
adopted.
For the development of an energy budget, shoot net primary produc-
tion was used to estimate belowground net primary production.
Since both
variables were measured concurrently from April 6 to May 16, 1981, these data
were used to establish the relationship between the net production of aboveground and belowground Zostera.
The specific growth rate for the net produc-
tion of aboveground and belowground Zostera was calculated by dividing the net
production (g dry weight m2) by the mean biomass (g dry weight m2) for the
period of time under consideration.
The ratio between specific growth rate
for aboveground Zostera and the specific growth rate for belowground Zostera
was calculated for that period of time.
while for transect 3 it was 0.46.
For transect 1 this ratio was 0.90,
It was assumed that the ratio between the
specific growth rates of ahoveground and belowground Zostera remained constant
throughout the study.
The specific growth rate for shoots was calculated for
each sample period, and the corresponding specific growth rate for belowground
Zostera was estimated using the appropriate ratio.
The estimate of the
specific growth rate for belowground Zostera then was multiplied by the mean
belowground biomass for the corresponding period of time to obtain the net
-259-
production of belowground Zostera.
The energy budgets based on these esti-
mates are presented in Tables 68 and 69.
At transect 1, throughout the study period, the biomass loss of belowground Zostera was greater than or nearly equal to the net primary production.
At transect 3, the biomass loss was generally between 25 and over 100% of the
net primary production for belowground Zostera.
Therefore, as was the case
for aboveground Zostera, belowground Zostera biomass was regularly being
turned over.
The large bioniass loss from the Macrophyte Primary Production subsystem
represented the coupling of this subsystem with the Detritial Decomposition
subsystem, as well as the Consumer Processes subsystem (Fig. 3).
Losses of
belowground biomass were primarily retained within the Zostera bed, while the
losses of aboveground biomass not retained within the Zostera bed were transported to other regions within the estuary, to the salt marsh and to the
ocean.
It was through this export of primarily aboveground biomass that
Zostera had an impact as an input of organic matter on regions distant from
its source.
At a higher level of resolution, processes associated with the Zostera
Primary Production subsystem were described.
The growing season for Zostera
in Netarts Bay was defined in April through October, which is typical of
temperate seagrass beds (Phillips, 1972; Sand-Jensen, 1975; Stout, 1976).
Since production data for months representing an entire growing season were
available only for transects 1 and 3, data from those regions were used as a
basis for the following estimates.
-260-
Table 68.
Energy budget accounting for the gains and losses of
belowground biomass along transect 1 between April 1,
Values are expressed as g dry
1980 and July 1, 1981.
weight nr2 for the period of time under consideration.
DATE
BIOMASS
APR
1, 1980
160.8
MAY
2,
1980
154.1
JUN
1,
1980
151.7
tBI0MASS
BIOMASS
ODU
- 6.7
-2.4
JUN 29, 1980
206.9
AUG 24, 1980
147.2
SEP 24, 1980
132.5
OCT 23, 1980
117.5**
6,
1981
126.1
MAY
3,
1981
124.4
MAY 30, 1981
151.6
JUL
130.0
*
1981
174.5
161.8
+42.5
167.1
124.8
-59.7
79.7
139.4
-14.7
105.1
119.8
-15.0
125.0
140.0
-55.5
-
-
+64.1
-
62.0
APR
1,
+12.7
164.4
JUL 26, 1980
FEB 12, 1981
1.7
150.3
152.0
+27.2
179.4
152.2
-21.6
197.1
218.7
Dashes indicates no data available.
**
Extrapolated.
-
-26 1-
Table 69.
Energy budget accounting for the gains and losses of
belowground biomass along transect 3 between April 1,
1980 and July 1, 1981. Values are expressed as g dry
weight nr2 for the period of time under consideration.
DATE
BIOMASS
APR
1,
1980
71.7
MAY
2,
1980
37.3
JUN 1, 1980
35.1
JUN 29, 1980
54.1
JUL 26, 1980
85.6
AUG 24, 1980
53.7
SEP 24, 1980
35.5
OCT 23, 1980
30.0
FEB 12, 1981
24.8
APR
6,
1981
41.0
MAY
3,
1981
31.4
BIOMASS
NET PRIMARY
PRODUCTION
BIOMASS
LOSS
-34.4
- 2.2
**
MAY 30, 1981
63.2
JUL 1, 1981
50.0
*
*
+19.0
31.2
12.2
+31.5
55.9
24.4
-31.9
34.8
66.7
-18.2
40.1
58.3
- 5.5
29.5
35.0
-5.2
-
+16.2
-
- 9.6
25.3
34.9
+31.8
18.9
-12.9
-13.2
39.6
52.8
Dashes indicate no data available.
Extrapolated.
-
-262-
The total net primary production of aboveground and belowground Zostera
and epiphytes for the entire growing season was obtained from the production
values measured for the period from April through October during the course of
the study.
Production expressed as g dry weight m2 day
dividing by 214 days, or the length of the growing season.
was calculated by
The dimensions of
the Zostera bed were measured and the bed was stratified into regions representative of transect 1 and transect 3.
17,562 m2.
The total area of the study site was
Of this total, an area of 10,062 m2 was designated as equivalent
to transect 1 and an area of 7500 m2 was designated as equivalent to transect
3.
The net primary production for each region was then estimated by multi-
plying its area by the production m2.
The turnover time was calculated from the following expression:
Mean biomass
Turnover time
(days)
during the period
from t1 - t0
(g
m2)
Net production
during the
period from
ti
tO
(g m2 day)
where t0 is the time at the beginning of the measurement period and t1 is the
time at the end of the measurement period.
Measurements of Zostera biomass expressed in g dry weight were converted
to g C by multiplying by 0.38, the proportion of the dry weight that is carbon
(Westlake, 1963).
Measurements of epiphyte biomass expressed as g dry weight
were converted to g C using the expression proposed by Davis (1982):
g carbon
g dry
weight
proportion ashfree dry weight
where 0.50 is the proportion of the ash-free dry weight that is carbon.
x 0.50,
-263-
The region represented by transect 1 accounted for 80% of the primary
production of the Zostera Primary Production subsystem (Table 70).
Although
the mean biomasses for aboveground and belowground Zostera were nearly equivalent in this region, aboveground biomass accounted for 58% of the net primary
production of the macrophyte, and was turned over about three more times
during the season than the belowground material.
In contrast, the region
similar to transect 3 maintained a mean belowground biomass that was 30%
higher than the mean aboveground biomass (Table 71). The aboveground biomass
turned over almost three times as fast as the belowground biomass, and its
rate of production was almost double that of the belowground biotnass.
Therefore, the plants in two regions of the bed had different growth
strategies.
The net primary production by the Epiphyte Primary Production subsystem
only accounted for 8% of the net primary production associated with the
Zostera Primary Production subsystem during the growing season (Table 72).
The mean turnover time for epiphyte assemblages was more than twice that of
the aboveground Zostera.
Stout (1976) reported that 161 ha in Netarts Bay were occupied by shallow
eelgrass beds.
for transect 3.
Her description of a shallow eelgrass bed was similar to that
She also reported that 176 ha were occupied by deep eelgrass
beds, i.e., equivalent to transect 1.
To calculate the production of the
entire bay associated with each region, the net primary production values
expressed in g dry-weight m2 for each region was multiplied by 10,000 times
the area of the region.
Therefore, an estimate of total annual net primary
production for the eelgrass beds in Netarts Bay was 6.0 x io6 kg.
Primary
Production
m
Subsyste
Zos tera
Primary
Production
m
Subsyste
Epiphy te
Macrophyte
Primary
Production
Subsys tem
26,500
(9400)
(948.0)
(4.4)
360.4
(121.9)
(6.9)
2713.8
57.7
(300)
302.7
(115.0)
2,500
12.12
247.4
(29.7)
(9100)
(918.3)
0.9
(0.1)
24,000
2416.5
(4.3)
(3800)
(381.2)
11.3
10,000
1003.1
4.7
(1.8)
Belowground
7.5
4.3
8.0
6.7
148.8
(5300)
(56.5)
9.2
153.9
(58.5)
14,000
1413.4
(537.1)
6.6
(2.5)
Aboveground
Zostera
Zos tera
X-OVER
XBIO
NPP/AREA
NPPm2
28.4
49.9
26.8
31.7
23.3
d-OVER
Annual net primary production for the region of the Zostera bed represented by
transect 1. A growing season from April to October was assumed. NPPd1 = net
primary production expressed as g dry weight ml da y1; NPPnr2 = annual net
primary production expressed as g dry weight m ; N PP/AREA = annual net primary
production for the entire area (10,062.5 m2) expres sed as kg dry weight; XBIO =
mean biomass expressed as g dry weight nr2; X-OVER = the number of times biomass
turned over; d-OVER = the number of days for the bi omass to tumover during the
growing season. The values in parentheses are the corresponding measurements
expressed as grams carbon.
NPPd1
Table 70.
-264-
Subs y s t
m
e
Primary
Production
Zos tera
m
Sub sy ste
Epiphyte
Primary
Production
Primary
Production
Subsystem
(1.3)
3.4
(0.01)
0.1
742.3
(272.5)
(4.4)
36.9
(2030)
5,600
(30)
280
(32.1)
88.4
(0.7)
5.8
(31.4)
(2000)
Zos tera
49.0
(18.6)
82.6
(700)
(92.8)
33.6
(12.8)
XBIO
5,300
18,000
244.1
1.1
(0.4)
Below g ro und
705.4
(268.1)
(1300)
3.3
(1.3)
35,000
461.3
(175.3)
2.2
(0.8)
Aboveground
Zostera
Mac rophy te
NPP/AREA
NPPm2
8.5
6.3
8.5
5.0
13.7
X-OVER
25.2
33.9
25.1
42.9
15.6
d-OVER
Annual net primary production for the region of the Zostera 1)ed represented by
transect 3.
A growing season from April to October was assumed. NPPd1 = net
primary production expressed as g dry weight m2 da v-i; NPPm 2 = annual net
primary production expressed as g dry weight nr2; NPP/AREA = annual net primary
production for the entire area (7500 m2) expressed as kg dry weight; XBIO = mean
biomass expressed as g dry weight in2; X-OVER = the number of times biomass turned
over; d-OVER = the number of days for the biomass to turnover during the growing
season. The values in parentheses are the corresponding measurements expressed
as grams carbon.
NPPd1
Table 71.
-265-
Sub sys tern
Zostera
Primary
Production
Subsys tern
Epiphyte
Primary
Production
Primary
Production
Subsystem
Macrophy te
Zos tera
Belowground
(4500)
(474.0)
(5.7)
15.6
1.0
(0.1)
(5.6)
448.8
(154.0)
32,100
(11,400)
(7.6)
(300)
(34.1)
3406.2
(1220.5)
63.5
2,800
284.3
385.3
(146.4)
(75.1)
11,800
1247.2
5.8
(2.2)
29,300
(11,100)
197.8
(6600)
(712.4)
3121.9
(1186.4)
187.5
(71.3)
17,500
1874.7
8.8
(3.3)
14.6
XBIO
NPP/AREA
NPPm2
NPPd1
7.6
4.5
8.1
6.3
10.0
X-OVER
28.2
47.8
26.4
33.9
21.4
d-OVER
Annual net pri mary production for th entire Zostera bed. A growing season from
= net primary production expressed as g dry
April to Octob er was assumed. NPPd
weight m2 day 1; NPPuf2 = net primary produ ction expressed as g dry weight nc2;
NPP/AREA = net primary production for the ent ire area (17,562.5 -2) expressed as
kg dry weight; XBIO=mean biomass expressed asgdryweight m; X-OVER = the
number of time s biomass turned over; d-OVER = the number of days for the biomass
to turnover du ring the growing season. The values in parentheses are the corresponding measur ements expressed as grams carb on.
Aboveground
Zostera
Table 72.
-266-
-267-
VI.
Discussion
The pattern of growth of Zostera marina L. in Netarts Bay, Oregon is
typical of Zostera growing in temperate regions.
However, the results of this
study also support the conclusion of McMillan and Phillips (1979) that
seagrass populations reflect the selective influence of local habitat
conditions.
In Netarts Bay, the initiation of growth in the spring is marked
by shoot proliferation, change to the summer morphology and rapid growth of
the leaves as Tutin (1942), Phillips (1972), Sand-Jensen (1975), Jacobs
(1979), and Harrison (1982) also found.
and early summer.
Flowering begins during the spring
Maximum vegetative growth occurs after the maximum density
of reproductive shoots is reached (Phillips, 1972).
In the late summer and
into fall, there is a gradual decline in shoot density and biomass.
Despite
agreement on this general pattern of events, reports differ as to the timing
and magnitude.
Sexual reproduction does not play a major role in the maintenance of
Zostera beds.
Reproductive shoots comprise on the average from 2.6% (this
study) to 15% of the total shoots in an area (Phillips, 1972; Sand-Jensen,
1975; Aioi, 1980; Harrison, 1982).
The timing of events associated with the
sexual reproduction of Zostera in Netarts Bay is very similar to that in Puget
Sound (Phillips, 1972).
Flowers appear in the bed from March to May and
disappear between August and October.
Although Phillips (1972) found seeds
germinating throughout the year, the time of peak seed germination in Puget
Sound (April to July) coincides with the time that seedlings were found in
Netarts Bay.
-26 8-
The leaf marking technique permits the analysis of the growth of indi-
vidual leaves on a vegetative shoot.
This study agrees with previous investi-
gations that most of the growth of a leaf occurs when it is the youngest and
next to the youngest leaf on the shoot (Sand-Jensen, 1975; Mukai, etal.,
1979; Jacobs, 1979).
Differences in the time it takes for a leaf to reach its
maximum growth reflect local differences in the P1 and number of leaves per
shoot, i.e., lifetime of a leaf (Table 73).
The life of a leaf on a
vegetative shoot in Netarts Bay is most similar to that reported by Jacobs
(1979) for Roscoff, France.
He reported a change in the number of leaves per
shoot and the PT during the course of his study.
As in this study, he noted
an increase in the number of leaves per shoot in the spring, and a decrease
during the summer and into the fall.
Moreover, he found a negative corre-
lation between the PT and isolation.
This was not the case for Netarts Bay,
where the PT was longer from June through August 1980, when photosynthetically
active radiation was maximum (Fig. 56).
Instead, changes in the lifespan of a
leaf in Netarts Bay were related to the regularly occurring annual changes in
the plant between the winter and summer shoot morphology.
Biotnass and density of Zostera in Netarts Bay, Oregon is comparable to
that for Zostera in other temperate regions (Table 74).
The highest densities
and biomasses were measured along transect 1 and are similar to the highest
densities and biomasses reported in the literature.
Reported values for production were converted to carbon following the
recommendations of Westlake (1 )63).
Values from the literature for
aboveground Zostera production range from 0.5 to 8 g C rn2 day'.
of this study are within these ranges, with 0.6 to 4.2 g C in2 day
aboveground Zostera production and 1.0 to 6.6 g C m2 day
production (Table 75).
The results
for
for total Zostera
Figure 56.
MONTH
JUN JUL AUG SEP OCT NOV DEC JAN FEB MAR APR MAY
4
16
Maximum photosynthetically active radiation (PAR) and mean plastochrone Interval (P1) of the
three transects from June 1980 to May 1981. PAR is expressed as E.m2.d; P1 is expressed
as days. PAR values were adapted from Davis (1982).
-JIO
r
F-2O
50
60
-269-
Table 73.
LOCATION
Japan
Plastochrone interval (P1), mean number of leaves per
vegetative shoot (LVES) and mean lifetime of a leaf
(LIFE) from data for various localities. P1 and LIFE
are expressed in days.
P1
LVES
8
5.5
LIFE
REFERENCE
44
Mukai, et al. (1979)
56
Sand-Jensen
Denmark
14
3.9-4.5
France
13-19
2.1-4.4
40-57
Jacobs (1979)
Oregon
9-20
2.7-4.0
34-56
This Study
Calculated from data
(1975)
Stout, 1976
This Study
Transect 1
Transect 2
Transect 3
710-2101
599-4576
671-1056
995-3845
789-1414
500-1761
186-324
62-1840
288-467
120-463
46-167
47-148
Alaska
Oregon
Only aboveground Zostera considered.
McRoy, 1966
McRoy, 1970a, l970b
151-893
116-231
Phillips, 1972
Keller, 1963
Waddell, 1964
Harding and Butler, 1979
Dillon, 1971
Penhale, 1977
Burkholder and Doheny, 1968
Harrison, 1982
Jacobs, 1979
Nienhuis and DeBree, 1980
Petersen, 1913
Sand-Jensen, 1975
REFERENCE
Washington
12_421*
6-192*
30-730
-
175-545
50_185*
North Carolina
California
-
50-160
580-700
0-3600
1200-1800
-
247-2062
5-15
Canada
*
DENSITY
New York
200-470
France
1-116
272-960
157-443
BIOMASS
Reported biomass and density values measured for Zostera marina L.
Biomass is expressed in g dry weight m2; densit y is expressed aS
numbers of shoots m2.
The Netherlands
Denmark
LOCALITY
Table 74.
-270-
Dillon, 1971
Penhale, 1977
Phillips, 1972
Marking
'4C Method
14C Method
Biomass
0.6_3.3*
0.5-1.7
0.6-1.2
0.7-4.0
France
North Carolina
Washington
2.5_6.6*
0.9_l.9*
1.4-4.1
0.7-1.7
0.5-1.4
3.3-3.8
Marking
This Study
Transect
Transect
Transect
This Study
Transect
Transect
Marking
1
3
1
2
3
McRoy, 1966
McRoy, l97Oa, l97Ob
Nienhuis and DeBree, 1980
02 Method
02 Method
Summation of aboveground and belowground production.
Oregon
Alaska
8.0
Jacobs, 1979
Marking
O.O_3.5*
The Netherlands
Petersen, 1913
Sand-Jensen, 1975
Biomass
Marking
2-7.3
1.4_3.7*
REFERENCE
Denmark
LOCALITY
METHOD
Net production values reported for the shoots of Zostera marina L.
Net
and for the whole plant (aboveground plus belowg round material)
production is expressed in g C nr2 day-.
PRODUCTION
Table 75.
-27 1-
-27 2-
As in this study, relationships among changes in shoot density, total
Zostera biomass and aboveground production are reported in the literature.
One such relationship is that described for transects 2 and 3 where changes in
shoot density, total Zostera biotnass and aboveground production followed a
similar pattern (Phillips, 1972; Neinhuis and De Bree, 1980; Aioi, 1980;
Harrison, 1982).
Another is the pattern described for transect 1 in this
study where shoot density is highest in the spring and decreases during the
summer as total Zostera biomass and aboveground production increases (SandJensen, 1975; Jacobs, 1979).
Sand-Jensen (1975) attributed the decrease in shoot density that he
observed to the loss of reproductive shoots during the summer.
However, he
reported that shoot density decreased from 1800 shoots m2 to about 1200
shoots m2, and that reproductive shoots accounted for no more than 4% of the
total density or about 72 shoots nc2.
Therefore, loss of reproductive shoots
cannot totally account for the change in density that he observed.
Jacobs
(1979) did not attempt to explain the pattern.
These patterns are explained by the hypothesis presented in this study
that there is a threshold leaf area per unit area of substrate.
Results of
this study indicated that this threshold value is between 7.5 and 11.0 m2
leaf m2 area of substrate.
When the leaf area per unit area of substrate is
below the threshold value, shoot density, total Zostera biomass and
aboveground production are positively correlated.
When the leaf area per unit
area substrate is above the threshold value, shoot density is negatively
correlated with total Zostera biomass and aboveground production.
For
example, the leaf areas reported by Phillips (1972) range from 2 to 8 m2 leaf
-27 3-
area of substrate.
Therefore, the leaf area at Puget Sound during the
time of his study was below the threshold value suggested by this study, and
as the hypothesis predicts, the shoot density and biomass values that he
measured increased and decreased together.
Considering the conclusion of
Dennison (1979) that Zostera adjusts to a decrease in light levels by
decreasing of leaf area, this threshold leaf area must represent a critical
reduction of light In the Zostera bed which results from self-shading.
Light is considered an important factor in the determination of the
distribution and production of Zostera marina (Burkholder and Doheny, 1968;
Sand-Jensen, 1975; Jacobs, 1979; and Mukai etal., 1980).
Sand-Jensen (1975)
clearly illustrated that the pattern of leaf production was closely related to
that of insolation, but not that of temperature.
The correlation between
insolation and leaf production is also supported by this study (Fig. 57).
This relationship explains the earlier and higher shoot production reported
for 1981 as compared to 1980.
Rates of leaf production for May 1981 were
comparable to those for July 1980, and photosynthetically active radiation for
May 1981 was comparable to that for July 1980.
The curves for photosynthetically active radiation and mean shoot production had a similar shape except during August 1980, when there was a
relatively sharp decrease in shoot production.
This decrease was attributed
to the bloom of Entermorpha prolifera in Netarts Bay.
No other study has
reported such an interaction between the seagrass community and the drift
algae.
There are few determinations of the biomass and productivity of the
epiphytes of seagrasses.
The most complete study of the production of Zostera
0
I0
MONTH
JUN JUL AUG SEP OCT NOV DEC JAN FEB MAR APR MAY
0
j
Zc)
0
20oI
40b
60 Lu a:
8O
I00ztE
a:'
>-cJ
a:°
I4O8
160
z
0
month.
PAR values were adapted from Davis (1982).
as Em2d-. Shoot net primary production is expressed as g dry weight m2
Figure 57. Maximum photosynthetically active radiation (PAR) and mean shoot net primary
production for the three transects from June 1980 to May 1981.
PAR is expressed
-J
(9
t-20
-40
U-
a:
.50
180
200
-274-
and its epiphytes is that of Penhale (1977).
Using the
method she estab-
lished that the ratio between the mean rates of the production for epiphytes
and Zostera was 0.74, i.e., 0.65 mg C (g dry weight' h' for the epiphytes
divided by 0.88 mg C (g dry weighty' h1 for Zostera.
The corresponding
value for this ratio determined in this study was 0.60.
Production values for Zostera and epiphytic assemblages determined
through the coupling of the '4C method and the leaf marking method are
comparable to those reported for by other investigators using only the
method (Table 76).
The only production values for the epiphytic assemblages
are those reported by Penhale (1977) and this study.
Mean primary production
of epiphytes in North Carolina is at the lower end of the range reported in
this study.
The mean biomass of aboveground Zostera and epiphytes reported by
Penhale (1977) was 105 g dry weight m2, while the mean biomass of aboveground
Zostera and epiphytes found in this study was 251 g dry weight m2.
studies 25% of the biomass was epiphytes.
In both
Therefore, the production values
reported in this study are higher than those reported by Penhale (1977)
because of the greater biomass in Netarts Bay.
It has been postulated that the constant replacement of the leaf biomass
on a shoot of seagrass is a control on the development of stands of epiphytes
(Sand-Jensen, 1977; ott, 1980).
Until this work, no study of seagrasses has
monitored the biomass of the epiphytic assemblage and related it to the
pattern of the loss of leaves from the macrophyte.
Sharp decreases in
epiphyte biomass measured on June 1 and August 24, 1980 were related to the
sloughing of particular groups of leaves.
When a transition in the growth
pattern of Zostera occurred, there was a greater loss of leaf biomass than
-27 5-
Table 76.
COMPONENT
Zostera
Comparisons of estimates of the primary production of
Zostera and associated epiphytic assemblages obtained
Production is expressed as g C nr2
by the 14C method.
day
LOCALITY
North Carolina
Alaska
Oregon
Epiphytes
North Carolina
Oregon
PRODUCTION
1.7
0.9
11.0
1.0-6.6
0.2
0.3-4.9
REFERENCE
Dillon, 1971
Penhale, 1977
McRoy, 1974
This Study
Penhale, 1977
This Study
-27 6-
usual, and a decrease in epiphyte biomass was noted.
Since new leaves are
continually being produced on a shoot, the epiphyte biomass that is lost is
also continuously replaced as the new tissue is colonized.
Phillips (1972) demonstrated that individual shoots of Zostera grown in
culture without epiphytes had a regular pattern of initiation and loss of
leaves.
Therefore, he hypothesized that the timing of the loss of leaves is
inherent to the Zostera plant and is not tied to any critical load of epiphytes.
Results of the Principal Components Analysis done in conjunction with
this study supported this hypothesis.
Epiphyte load was highly correlated
with one of the principal components, while the other variables considered
were correlated with the two other principal components.
components represented orthogonal axes.
These principal
Therefore, epiphyte load may be
independent of these variables or may be associated by complex non-linear
relationships.
There are few studies in the literature that attempted to partition the
changes in the biomass of Zostera as was done in this study.
This is
primarily because the techniques for measuring belowground production were not
developed until recently.
Sand-Jensen (1975) and Jacobs (1979) reported
annual production of the Zostera beds in their localities partitioned into
aboveground, belowground and total Zostera (Table 77).
The values for Netarts
Bay are higher, although the Zostera biomasses for all three areas are
similar.
This study was designed to augment the ongoing work of the EPA relative
to physical processes in the estuary.
The coupling of these studies was
designed to test the hypothesis that nutrient dynamics in Netarts Bay during
the growing season (April through October) are closely related to the
856
241
1097
1874.7
1247.2
3121.9
Aboveground
Belowground
Total
Aboveground
Belowground
Total
(g dry wt.
PRODUCTION
(g
712.4
474.0
1186.4
415
87
328
389
183
572
dni2)
Apr.-Oct.
Apr.-Oct.
12 months
DURATION OF
EXPERIMENT
This Study
Sand-Jensen, 1975
Jacobs, 1979
REFERENCE
Mean values of annual ne t primary production values partioned into aboveground
and belowground Zostera.
1116
492
1608
77.
Aboveground
Belowground
Total
TaiDle
-277-
-27 8-
biological processes associated with the Zostera Primary Production subsystem.
The future application of the results of this study will involve the development of a holistic conceptualization of the estuary.
Data related to the
benthic algal flora reported in an earlier section can be integrated with data
from the Zostera decomposition work done by the EPA (unpublished data), and
used to describe changes in biomass associated with the Algal Primary Production and the Detrital Decomposition subsystems.
These two subsystems can be
then coupled with the dynamics of the Zostera Primary Production subsystem to
describe the dynamics of the Primary Food Processes, a subsystem at a coarser
level of resolution.
In addition to describing the changes in biomass associated with each of
the subsystems and their couplings, an understanding of the dynamics of the
physical processes under investigation by the EPA will provide a knowledge of
the driving variables that affect these subsystems.
This synthesis of
biological and physical processes will contribute to the understanding of the
fundamental mechanisms regulating processes common to many estuaries.
-279-
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1979a.
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1979b.
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-28 0-
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1980.
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1981.
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1971.
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Distribution of intertidal
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The ecology of Amamo (Zostera marina) and Koamamp
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Appendix I.
Summary tables for the analysis of variance associated with the
concentration of organic matter in the top cm of sediment (AFDW), the
concentration of chlorophyll a in the top cm of sediment (CHLS), the
ratio of chlorophyll a concentration in the top cm of sediment to that
of the 4-5 cm depth (RATIO), gross primary production (GPP), community
oxygen uptake (0UPTK), the ratio of gross primary production to
community oxygen uptake (GPP/CR), and the ratio of gross primary
production to the chlorophyll a concentration in the top cm of sediment
(ASSIM).
T level refers to tidal level and Sediment refers to
Intensive study site (SAND, FINE SAND and SILT).
Variable
AFDW
CHLS
Source of Variation
Main Effects:
Sediment
T Level
Time
DF
Mean
Square
10
90787.815
2010000.000
33000.744
20897.522
17.67
391.23
6.42
4.07
.001
.001
.005
.001
12.94
0.87
1.59
n.s.
.001
.001
.005
.001
15
2
3
2-Way Interactions:
Sediment by T Level
Sediment by Time
T Level by Time
6
66479222
20
29
4464.136
Error
53
5137.643
Main Effects:
Sediment
T Level
Time
16
50412.211
153618.336
44862.896
32615.977
5.99
18.26
5.33
3.88
11.80
.001
1.15
n.s.
n.s.
2
3
11
8192 .516
2-Way Interactions
Sediment by T Level
Sediment by Time
T Level by Time
22
31
99244.404
9656.430
7815.200
Error
57
8413.847
6
0.93
.001
.10
-308-
Appendix I (continued)
Variable
RATIO
Source of Variation
Main Effects:
Sediment
T Level
Time
5.13
10.22
14.41
1.67
1.77
2.91
29
26368.678
7625.724
19719.394
Error
53
9065.748
Main Effects:
Sediment
T Level
Time
11
9734.859
11198.406
1503.358
11141.728
2.22
2.55
0.34
2.54
13
3234.046
3347.967
3114.239
0.74
0.76
0.71
Error
23
4388.343
Main Effects:
Sediment
T Level
Time
11
1223.388
2433.902
204.966
1093.928
3.81
2.99
1.27
1.26
2-Way Interactions:
Sediment by T Level
Sediment by Time
T Level by Time
OUPTK
Mean
Square
46467.122
92638.673
130603.101
15117.787
2-Way Interactions:
Sediment by T Level
Sediment by Time
T Level by Time
GPP
DF
15
2
3
10
6
20
2
2
7
4
14
2
2
7
2-Way Interactions:
Sediment by T Level
Sediment by Time
T Level by Time
14
13
959.737
406.282
403.892
Error
23
320.851
4
0.84
7.59
0.64
3.41
-309--
Appendix I (continued)
Variable
ASSIM
Source of Variation
Main Effects:
Sediment
T Level
Time
DF
11
2
2
7
Mean
Square
6.055
6.794
0.583
7.076
2-Way Interactions:
Sediment by T Level
Sediment by Time
T Level by Time
14
13
0.677
3.803
2.801
Error
23
3.759
4
1.61
1.81
0.16
1.88
0.18
1.01
0.75
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.