INTERNAL REPORT
148
ALLOCHTHONOUS MATERIAL INCOME
AND DECOMPOSITION IN FINDLEY LAKE
G. Rau and R. Gara
University of Washington
INTRODUCTION
Aquatic ecosystems are open; as systems they receive and discharge water,
nutrients and energy through the boundaries imposed by air and land.
and
These air-land-water interactions might be better conceptualized
from
strictly
an
studied if the system under investigation were enlarged
watershed.
aquatic one to a system which also includes the surrounding
In any case it has been shown that the limnology of water bodies can be
profoundly influenced by and dependent upon terrestrial materials which
enter via hydrologic and atmospheric pathways.
Studies of lotic systems, reviewed in Hynes (1970) have discovered that,
is the
in some cases, naturally occurring foliage and insect litterfall
Higher
numbers
of
chain.
food
primary energy source for the aquatic
alone
are a
by
aquatic
primary
production
consumers than can be supported
Recently,
several
frequent occurrence in running water environments.
researchers have shown that naturally introduced allochthonous material
also can be important in lake systems as well (Sorokin 1972, Sorokin
and Kadota 1972, Yamamoto 1972, Efford 1969, 1972).
In a subalpine setting, Findley Lake is surrounded by a 162-ha cirque
basin 60% of which is forested by Pacific silver fir and mountain
hemlock (Del Moral 1973). The lake itself is described by Hendrey
(1973) as oligotrophic and nitrogen-phosphorus-light limited during a short
four-month "growing season." He estimates autotrophic capacity to be 530
kg carbon fixed per year. How does this carbon production in the lake
compare with sources entering from the surrounding terrestrial environment?
What contributions might terrestrial and atmospheric sources of nitrogen
and phosphorus make to the lake's limited budget of those elements?
What is the seasonal and spatial nature of this income and does biological
activity in the lake coincide with it? While Larson (1973) and Hendrey
(1973) both state that allochthonous material probably influenced biological
activity in the subalpine lakes they studied, the actual income and
ultimate importance of this material has received little attention.
The 1973
objectives of this study were to: (1) identify the various
sources and pathways of foreign substances entering Findley Lake; (2)
develop and employ techniques of sampling allochthonous income for the
purposes of qualitatively and quantitatively describing its characteristics
Findley Lake allochthonous material
Rau and Gara
on a per-square-meter and, eventually, on a per-lake basis; and (3) monitor
weight loss, chemical change, and decomposer succession on a dominant litter
This decomposition study will
type (conifer needles) entering the lake.
elucidate what contribution an important type of allochthonous material makes
to the lake's chemistry and biology.
METHODS AND MATERIALS
With regard to methods for sampling allochthonous material,
Edmondson states the following:
Dr. W.T.
"Few studies of aquatic productivity have evaluated these
thonous) sources, and there is no standardized procedure.
(allochSome of
in lakes or drift
this material will be taken in sediment traps
traps in streams, but part of it may not be identifiable as to
origin. It is recommended that all investigators be prepared to
recognize such sources of income to their lakes or streams and to
what they
p.
1
can to evaluate
it (W.T.E.)"
(Edmondson and Winberg
do
1971,
26)
Development of sampling and analytical procedures amenable to
study site was then a prime objective of this study.
the remote
A conceptual model of
the process under investigation is shown in Figure 1.
Atmospheric Income
Sampling during snow/ice cover
A 6-cm-diameter snow corer was used to take cores on and around the lake
snow cover in both random and transect fashion (Figure 2). By sampling
onshore, a known distance offshore, and at the lake center, a mathematical
function of dry weight of total solids (or some other measurement of
allochthonous material) per core vs. distance from shore could be fitted to
Thus the total litter content of the lake snowpack and therefore
the data.
the potential income during spring melt could be estimated.
Frozen cores were originally transported and stored in plastic bags at
-5°C. They have since been melted and transferred to acid-rinsed poly
bottles stored at 5°C. While arrangements for lab facilities have yet to be
made, total organic carbon and Kjeldhal nitrogen, and total phosphorus would
seem the most appropriate chemical parameters to be measured. Cations,
lignin,
cellulose,
pollen, and so on are other possibilities.
Sampling during the snow-free period
Studies of terrestrial litter and insect fall have used
screens, funnels, pans, sticky surfaces, and the like.
numerous kinds of
For the snow-free
summer months the litter trap design ultimately used to sample airborne
material consisted of nested buckets suspended in the center of an inflated
inner tube, which then was floated on the lake surface and tethered in
position by polypropylene cord and rock anchors. Black buckets were used to
avoid attraction of
insects.
To retain large particulate material, the
bottom of the top bucket was replaced with 1-mm2-mesh fiberglass screening.
2
Findley Lake allochthonous
material
Rau and Gara
The second bucket, nested below the first, was not modified and it collected
the fine particulate and dissolved fractions plus precipitation.
The collection procedure involved picking the screen of the top bucket and
storing the material in glass vials. Separation of plant and insect
material was done in the lab with the insect portion stored in 70% alcohol
and the plant material in aluminum trays at 60°C.
A slurry of the contents of the bottom bucket was made by vigorously
scrubbing the inside of the bucket with a nylon brush and thoroughly
mixing the liquid present. A 250-ml sample was then taken after the slurry
volume was measured. If the initial slurry volume was less than the amount
required for sampling, 250 ml of distilled water was added prior to
scrubbing. The samples were stored in acid-rinsed polybottles at -5°C.
After the collection procedure, the buckets were scrubbed and rinsed in
lake water, shaken dry, and returned to their sampling position.
Two sampling schemes were used; one was a random design, similar to the one
used for snow coring, and the other employed transects of buckets. The
random design ignored terrestrial type and randomly placed three traps in
each of these areas: 10 m inshore, at the land-water interface, and 10m
The transect scheme placed a transect of three traps in a given
offshore.
terrestrial type inshore, onshore, and offshore as above (Figure 3).
While it will be possible with both sampling designs to estimate total
airborne income during the open season, the latter scheme will investigate
the qualitative and quantitative aspects of litterfall emanating from
various terrestrial types.
Hyclro Zogic Income
As the snowpack began to melt in the spring of 1973, several streams
Heretofore, the significance
flowing into Findley Lake became exposed.
of these intermittent streams had been discounted and the identification
It became clear,
and measurement of these inputs had not been anticipated.
the
lake
along with
however, that sizable volumes of water were entering
As
these
and
dissolved
material.
an unknown quantity of particulate
of
flow rate
inflows became uncovered, trimonthly to monthly measurements
and sediment load (1-mm2 mesh) were taken.
Stream discharge was calculated by estimating the volume contained in a
given section of stream channel and dividing this volume by the average
time it took a floating object to travel through the channel section
(Hewlett and Nutter 1969).
The sediment load was sampled by placing a galvanized screen 1-mm2-mesh
After a known amount of time the screen
size) across the entire channel.
was removed and the retained material was placed in tins, returned to the
The dried samples are presently being
lab, dried at 60°C, and weighed.
Arrangements have been made with
stored in containers at room temperature.
the Biome's lab at Oregon State University for chemical analysis of this
material.
Some water samples were taken by Dr. Mike Singer for chemical analysis.
Further sampling during the fall runoff period will be done.
Findley Lake
allochthonous material
Rau and G3 ra
De composition Study
Needles from both Pacific silver fir and mountain hemlock surrounding tile
lake were found to comprise a sizable fraction of the large particulate
material entering the lake. Needles have been shown to be the dominant
litter type in conifer forests bray and Gorham 1964, Abee and Lavender 1972).
In an effort to elucidate the contribution this material migiht snake to the
energy and nutrient budget of the lake, an aquatic decomposition study was
initiated in the summer of 1973 and will be completed in 19?4. By retaining
known amounts of needles in semi-open containers on the lake bottom,
oeighc l-ass and chemical change of conifer needles during a 10-to 12-monthdecomposition period will he monitored. The containers used include nylon
net bags of two mesh sizes and slotted plastic, tape canisters.
During midsummer, branches were cut from several fir (Aries (vnabiZis), end
After drying at
hemlock (T°z*a merten.eiana) on the shore of Findley Lake.
Two sets of
'60°C several kilograms of needles were stripped or shaken off.
forty 20- X 20-cmnylon net bags were constructed, one set being of 500-um-mesh
nylon netting and the other of 73-dam Nytex netting. Half the bags in each
set were filled with approximately 12g of hemlock needles, the remaining
All bags were dried at 60°C for
bags with the same amount of fir needles.
five days, weighed to the nearest milligram, and closed with tagged,
stainless steel safety pins.
Arrays of each needle type were constructed by skewering needles onto
Forty arrays each of hemlock and fir
color-coded stainless steel pins.
The arrays were dried at 60°C for Five days, weighed to
needles were made.
the nearest 0.1 mg and fastened inside slotted plastic tape canisters.
Ten such canisters were prepared, each containing four hemlock and four
fir needle arrays.
The canisters and 30 bags were transported to the lake. Along a transect in
approximately 3.5 m of water located near the southwest shore (see Figure
t!),
10 clusters of each bag type and the 10 canisters were lowered to the
A bag cluster for either the 500- or the 73-arm lag types
lake bottom.
consisted of two bags of hemlock needles and two bags of fir needles,
the four bags were fastened to a common rock anchor and lowered to the
Additionally, five blank bag clusters and canisters
bottom with nylon line.
were lowered to investigate possible container effects on weight loss and
biological activity.
After 10 days and monthly thereafter,
one 500 pm ban cluster,
one 73-um bar,
cluster, together with an array-containing canister will be raised from the
The bags and arrays will be dried for five days at 60°C and
transect.
weighed. Bag contents will then he sent to the Oregon State University
Biome laboratory for chemical analysis.
PRELIMINARY RESULTS AND DISCUSSION
Because most of the research efforts until now have been spent on sampling,
only a preliminary analysis of these samples has been done. More time is
being devoted to sample analysis now that the summer field season has ended.
If
Findley Lake a] lochthonous material
Rau and Gara
Atmospheric Input
During snow/ice cover
All but one set of snow corings remain stored awaiting chemical analysis.
Surface cores taken 21t May just prior to breakup were dried at 60°C in
preweighed plastic weighing boats. The dry weight of the remaining
The data support the
nonevaporated material is shown in Figure 5.
hypothesis that the amount of airborne material, probably originating in
the forest canopy, decreases as a nonlinear function of distance from
Either an exponential decay or second-degree polynomial equation
shore.
will be fitted to the dry weight, carbon, nitrogen, and phosphorus data
Total income to the
as they become available on all the cores taken.
lake for any of the above parameters might be estimated by assuming the
lake to be a perfect circle and integration below the surface generated by
rotating the decay equation above that circle.
Sizable amounts of nitrogen and phosphorus are present in coniferous
forest litterfall (Bray and Gorham 1964, Abee and Lavender 1972) and in the
In this study, the input
snowpack surrounding Findley Lake (Singer 1971).
of nutrients and fixed carbon to the lake snowpack and ultimately to the
lake itself will be investigated.
During the open season
A large amount of airborne particulate and dissolved material has been
collected and awaits chemical analysis and plant/insect material identification and enumeration. The litter traps have generally performed well
despite some disturbance from bear, elk, and wind. For a One-month
sampling period, 25 July to 23 August, the dry weight of large particulate
(>1 mm2) plant litter collected from each trap was measured. Figure
a graph of the mean litterfall for each area sampled versus distance
inshore traps. Again, a nonlinear exponential
describes the relationship.
6 is
from
decay function well
Hydrologic Inputs
Figure 3 shows the declining trend of discharge as snowmelt is completed in
early summer; sediment load similarly decreases (Figure 9). Preliminary
analysis of this sediment by the OSU Biome laboratory shows approximately
95% of this material is nonash, roughly 401, of which is lignin. Using an
average daily sediment discharge of 10 g per stream approximately '.(, kg
dry weight of material enters the lake during spring melt from the four
streams measured, and perhaps twice that amount of the remaining inflows
are considered.
DE compooi-i:ion ,tu(y
In an attempt to demonstrate
produced
of nylon
the decomposition process of terrestrially
lake, 10 sample sets
containing two conifer needle types were
organic material which naturally enters the
bags and canisters
A set of each container type ,jas
placed in the lake on 25 September 197
pulled from the lake 5 October 1973. Some colonization by fungi was
evident together with the
presence,
on the 500-pm bags, of chironomid
5
Findley Lake allochthonous
Rau and Gara
larvae.
Some invertebrates including
material
two caddisfly larvae were found
needle arrays. They were collected
within the plastic canister and on the
and stored in alcohol. The succession of invertebrates especially in the
canisters will be noted as the decomposition study progresses. No further
data are available at this time.
REFERENCES
ABEE, A., and D. LAVENDER.
litterfall
1972.
Nutrient cycling in throughfall and
J. F. Franklin,
IN:
Douglas-fir stands. p. 133-143.
coniferous
L. J. Dempster, and R. H. Waring (eds.), Proceedings--Research on
Service,
Portland.
Forest
forest ecosystems--A symposium, USDA
in 450-year-old
Litter production in forests of the
1964.
BRAY, J. R., and E. GORHAM.
J.
B.
Cragg
(ed.) Advances in ecological research,
IN:
world. p. 105-152.
264 p.
Vol. 2.
DEL MORAL, R.
89(1):26-40.
1973.
The vegetation
of Findley Lake basin.
Am. Mid]. Nat.
A manual on methods
1971.
EDMONDSON, W. T., and G. G. WINBERG (eds.).
IBP Handbook
of
secondary
productivity
in
fresh
waters.
for the assessment
Blackwell Scientific, Oxford. 358 p.
#17.
Energy transfer in Marion Lake, B. C., with particular
1969.
EFFORD, J. E.
Proc. Int. Assoc. Theor. Appl. Limnol. 17:104-108.
reference to fish feeding.
IN:
1972. An interim review of the Marion Lake project.
EFFORD, J. E.
problems
of
freshwaters,
Z. Kajak and Hillbricht-Ilkowska (eds.), Productivity
Polish Scientific, Warsaw. 918 p.
p. 88-109.
Productivity and growth kinetics of natural phyto1973.
HENDREY, G. R.
plankton communities in four lakes of contrasting trophic state. Ph.D.
thesis, Univ. Washington, Seattle.
HEWLET, J. D., and W. L. NUTTER.
137 p.
Univ. Georgia, Athens.
1970.
HYNES, H.B.N.
The
1969.
P.
An outline of forest hydrology.
ecology of running
waters.
Univ. Toronto Press.
1972.
Productivity Problems
555 p.
KAJAK, Z. and A. HILLBRICHT-ILKOWSKA (eds.).
of
Freshwaters.
Polish Scientific, Warsaw.
1973. A limnology study of a high mountain lake in Mount
Rainier National Park Washington state, USA. Arch. Hydrobiol. 72(1):10-48.
LARSON, G. L.
Chemical analysis of Findley Lake snow pack.
CFB Internal Report #48.
SINGER, M.
J.
SOROKIN, Y. I.
IN: Z. Kajak
Freshwaters.
1971.
unpublished.
Biological productivity of Rybinsk reservoir. p. 493-503.
and A. Hillbricht-Ilkowska (eds.) Productivity Problems of
Polish Scientific, Warsaw.
1972.
6
Findley Lake aiiocntnonous material
Rau and Gara
SOROKIN, Y.
sition in
I., and H.
freshwaters.
KADOTA.
1972.
Blackwell
Microbial production and decompoOxford.
Scientific,
Trophic structure in Lake Tatsu-Numa, an acidotrophic
special reference to the importance of the terrestrial
community. p. 405-419. IN: Z. Kajak and A. Hillbricht-Ilkowska, (eds.)
Productivity Problems of Freshwaters. Polish Scientific, Warsaw.
1972.
YAMAMOTO, G.
lake in Japan, with
is
7
Terrestrial
Atmospheric
C, NIP
Insect
Al iochthonous inputs
Emergence
Living
C,N,P
Meteorologic
Hydrologic
N
Decor oscrS 1
Consumers
OutflowI
I
L[-Pr-o-Ld--ucers-JJ
Plankton + Benthos
Sediment
- Transfer under
Investigation
Flow
Figure I. A Simplified Diagram of Carbon, Nitrogen, and Phosphorous
in a Coniferous Watershed
0
i
lOOm
J
o March 27- Random
0 April 13-Random
e May 24-Transect
Q Multiple Sample Site
Sample Site
Figure 2. Location of Snow Coring
o Transect Sampling.
Scheme
O Random Sampling
Scheme
Figure 3.
Location of Litter Traps
0
loom
J
L
N
Figure 4.
Location of Aquatic Decomposition
Study Site
N
X
Each core sampled a surface area of 28.2 cm 2
to a depth of 2 cm of snow
Cores taken May 24, 1973
3
0
C
N
a..
w 2
Mean
'D
Range of 2 cores
a)
J
I
0
I
I
20
50
100 meters
Distance from shore
Figure 5. Dry Weight of Litter in Surface Snow Cores vs.
Distance from Shore
0.6,
0.5
Sampling period: July 25-August 23, 1973
Each trap sampled an area of 615 cm 2
0.4
0.3
Y 0. 5907 e
-0.204-X
4-
0.2
0.
Eland
0
0
-
shore-
line -water
20
Distance from inshore litter trap-meters
10
Figure 6. Mean Plant litter `"/eight PerTrap vs.
Distance from Inshore Trap
X
0
I
Figure 7.
Location of Intermittent Stream
Discharge into Findley Lake
Figure 8. Discharge of Inflowing Streams
June 24
F-63.2g
C-48.68 C
F
i
15
O
i
C
0
F\
A
24
4
Day
B--B
7
212427
F
C
.D
5
13
July
Figure 9. Discharge of Sediment from Inflowing Streams
(Sediment approximately 95 % organic)
Month
May
June
20