EVPP 550
Waterscape Ecology and
Management – Lecture 11
Professor
R. Christian
Jones
Fall 2007
Lake Biology – Fish
Major Freshwater Groups
• Salmonidae
Brook Trout – native to E. US
– Trout and salmon
– Distribution
• Clear, cool waters
• Rivers & streams:
moderate to swift
• Lakes: cool & well
oxygenated
Rainbow Trout – native to W. US
– Food sources
• Aquatic insects
• Small fishes
Lake Whitefish – native to Gt. Lakes & other northern lakes
Lake Biology – Fish
Major Freshwater Groups
• Esocidae
Northern Pike – native to E. US
– Pikes, muskellunge
– Distribution
• Shallow, weedy
waters
• Large clear lakes &
ponds
• Slow-moving rivers
– Food sources
• Small fishes
Chain Pickerel – native to E. US
Muskellunge – largest pike –
native to E. US
Lake Biology – Fish
Major Freshwater Groups
Blacknose dace – very common
native
• Cyprinidae
– Minnows, chubs,
dace, shiners
– Most are small
– Distribution
Creek chub –
common creek
forage fish
Golden shiner –
native forage fish
• Widespread in both
lakes and stream
– Food supply
• Aquatic insects
• Small crustacea
• Oligochaetes
Common carp – native of Eurasia – can get
large
Lake Biology – Fish
Major Freshwater Groups
• Catostomadae
– Suckers
– Distribution
• Widespread in lakes
and streams
Northern hogsucker – creek
fish that eats periphyton
– Food supply
•
•
•
•
Aquatic insects
Small crustacea
Oligochaetes
Periphyton
Silver redhorse
White sucker – common and tolerant creek fish
Lake Biology – Fish
Major Freshwater Groups
• Ictaluridae
– Catfish, bullheads
– Distribution
Margined madtom – very small
creek fish
• Slow-moving still
waters often with
muddy bottoms
– Food supply
• Aquatic insects
• Oligochaetes
• Benthic items
Black bullhead – common in
Potomac
Channel Catfish – native to S. US – can get 20 lb
Lake Biology – Fish
Major Freshwater Groups
• Centrarchidae
Bluegill sunfish
– Sunfish, bass, crappie
– Distribution
• Widespread, tendency to
warmer waters
– Food supply
•
•
•
•
Pumpkinseed sunfish –
common in ponds and lakes
Aquatic insects
Crustacea
Molluscs
Fish (in large individuals)
Largemouth bass – common
piscivore in lakes and ponds
Lake Biology – Fish
Major Freshwater Groups
• Percidae
– Perches, darters
– Distribution
Tesselated darter – small creek and
lake species
• Widespread
– Food supply
•
•
•
•
Aquatic insects
Crustacea
Molluscs
Fish in larger
individuals
<>
Yellow perch – common early spring spawner
Walleye – large lake and river
species
Lake Biology – Fish
Global Distribution
Lake Biology – Fish
Global Distribution
Lake Biology – Fish
Trophic Roles
• Planktivores
– Mostly zooplankton
– Some (eg Tilapia) eat
phytoplankton
– Some are filter
feeders, strain
plankton through gill
rakers (whitefish,
gizzard shad)
– Others attack
individual zooplankton
(bluegill sunfish)
Lake Biology – Fish
Trophic Roles
• Benthivores/
Detritivores
– Some selectively feed
on individual prey
(trout)
– Some consume bulk
bottom material
(catfish)
– Often looking for
benthic inverts, but
consume detritus and
bacteria as well
– Some (suckers) feed
on periphyton too
Lake Biology – Fish
Trophic Roles
• Piscivores
– Feed on other
fishes
– Often will eat
young of their own
species
– Largemouth &
smallmouth bass
– Muskellunge
Lake Biology – Fish
Life History
• Most fish reproduce
annually over a fairly
short period producing a
cohort
• Reproduction often
occurs in spring or early
summer in temperate
areas
• Eggs hatch rapidly and
larvae progress to
juveniles over a few
weeks
• Sexual maturity (adult
status) may be reached in
1-3 year
Lake Biology – Fish
Life History
• Larvae are poor
swimmers and if in the
water column, they are
considered plankton –
ichthyoplankton
• Larvae feed on small
zooplankton (rotifers,
cladocera, nauplii)
• Some fish build nests &
guard eggs and larvae
• Newly hatched larvae
called “young-of-the-year”
Size structure of a fish
population related to age
classes (cohorts)
Note much lower numbers of
2 and 3 year olds: mortality or
age class strength?
Lake Biology – Fish
Factors affecting growth
• Temperature
– Has a strong effect
on growth rate and
feeding rate
– Cold water species
reach maximum
growth rates at
lower temperature
Lake Biology – Fish
Factors affecting growth
• Temperature
– Also has an effect on spawning success
– Warmer summer temperatures may allow young-of-the- year to
become large enough to avoid winter predation
Effect more
consistent for
pike
Lake Biology – Fish
Factors affecting growth
• Food Supply
– White perch ate
large numbers of
both zooplankton
and benthos in
spring
– Benthos
(chironomid larvae)
became more
important in
summer and fall
White Perch feeding in
Gunston Cove
Lake Biology – Fish
Factors affecting growth
• Food Supply
– Fish exercise selectivity
– Gut contents have different contents than the environment
White perch in
Gunston Cove
Much more scatter in
environment (benthos
and zooplankton) than
in the fish stomachs
Fish stomach biased
toward chironomid
larvae, environment
has a lot of
oligochaetes and
zooplankton too
Lake Biology – Fish
Factors affecting growth
• Food Supply
– As they pass through
the larval stage, fish
may exert strong
pressure on larvae for
a limited time and then
move on to other food
– Zooplankton rebound
both in numbers and
size
Oneida Lake: June through Oct
period shown
Strong pressure by age-0 yellow
perch abates as their number
decreases
Lake Biology – Fish
Patterns of Abundance & Production
• Resource & Habitat Partitioning
– Partitioning is thought to have evolved to minimize
competition
Lake Biology – Fish
Patterns of Abundance & Production
• Habitat Selection
– Many fish prefer vegetation and collections are often
greater at night
Lake Biology – Fish
Patterns of Abundance & Production
• Effect of variable year classes
– Fish populations are often dominated by individuals from
particularly strong year classes (ex 1959, below)
– Many years can have very low success
– Can track successful years over time
Lake Biology – Fish
Patterns of Abundance & Production
• Effect of Bottom Up
Processes
– In Virginia reservoirs a
strong correlation was
observed between total P
(“base” of food web) and fish
production (top of food web)
– Correlation also held when
looking at a single lake
(Smith Mountain Lake) over
time
Lake Biology – Fish
Patterns of Abundance & Production
• Effect of Bottom Up
Processes
– The same trend but with
a different slope has
been found in other
systems
Lake Biology – Fish
Patterns of Abundance & Production
• Effect of Bottom Up
Processes
– A similar relationship has
been observed
comparing fish
production and primary
production
– These all argue for
bottom-up control of fish
production
Lake Biology – Fish
Patterns of Abundance & Production
• Top Down Processes
– The imporance of topdown processes is
emphasized by the
Trophic Cascade model
Management of Freshwater
Systems
• Freshwater is a valuable
resource for:
–
–
–
–
–
–
Drinking water
Living resources
Food supplies
Irrigation
Transportation
Other
• It’s use may be impaired
by pollutants
– Decomposable organics
(BOD)
– Excess nutrients
– Acidification
– Toxic chemicals
– Hormones
– Erosion and Sedimentation
– Salinization
– Other
Management –
Decomposable
Organics
• Human and
animal waste is
very rich in
partially
decomposed
organic matter
and other
substances
• When placed in a
water body either
directly or via a
conveyance
system (sewer)
this can be very
destructive
Managemenent –
Decomposable Organics
• The input of raw or poorly
treated sewage creates a
whole chain reaction of
problems downstream
• Immediately below the release,
BOD (decomposable DOC)
and ammonia are highly
elevated which stimulates
bacteria and causes rapid
depletion of DO, often to 0
• As water moves farther
downstream, the BOD is used
up, but it takes longer to
oxidize the ammonia (through
nitrification)
• In zone II, algal blooms are
rampant because P has not
been removed and now other
conditions are favorable
Management –
Decomposable
Organics
• Sewage treatment
facilities typically strive to
remove BOD and solids
through sedimentation
(primary trt)and microbial
breakdown (secondary
trt)
• More advanced facilities
try to remove N&P
• Basically, you try to move
what would happen in
nature into a controlled
setting that doesn’t
impact the natural
environment
Excess Nutrients – N&P
Natural Eutrophication
• Productivity of lakes are
determined by a number
of factors:
– Geology and soils of
watershed
– Water residence time
– Lake morphometry
– Water mixing regime
• Over thousands of years
these factors gradually
change resulting in lakes
becoming more
productive
Cultural Eutrophication
• Human activities can alter
the balance of these
factors, esp. when excess
nutrients (P in freshwater)
are introduced
• Untreated sewage for
example has a TP conc of
5-15 mg/L
• Even conventionally treated
sewage has about ½ that.
• Compare that with inlake
concentrations of 0.03 mg/L
that can cause eutrophic
conditions
• So, even small amounts of
sewage can cause
problems
Cultural
Eutrophication
• Problems associated with
cultural eutrophication include
– Anoxic hypolimnion
• Part of lake removed as
habitat
• Some fish species eliminated
• Chemical release from
sediments
– Toxic and undesirable
phytoplankton
• Blooms of toxic cyanobacteria
• Phytoplankton dominated by
cyanobacteria and other
algae that are poor food for
consumers
– Fewer macrophytes
• Elimination of habitat for
invertebrates and fish
– Esthetics
Cultural
Eutrophication
- Management
• Source controls
– Diversion
• One of the first
methods tried
• Sewage captured
and diverted
outside lake to say
large river or ocean
– Advanced wastewater
treatment
• More desirable now that
technology exists
Cultural
Eutrophication –
Case Studies
• Lake Washington
– Following WWII, pop’n
increases in the Seattle
area resulted in increases
in sewage discharge (sec
trted) to Lake Washington
– Secchi depth decreased
from about 4 m to 1-2 m
as algae bloomed from
sewage P
– Diversion system was
built and effluent was
diverted to Puget Sound
in mid 1960’s
– Algae subsided and water
clarity increase
– Daphnia reestablished
itself and further clarified
the lake
Cultural
Eutrophication –
Case Studies
• Norfolk Broads, England
• Shallow systems where
macrophytes dominated
• Increased runoff of
nutrients, first from
sewage and then from
farming stimulated algae
• First periphyton bloomed
and caused a shift from
bottom macrophytes to
canopy formers
• Then phytoplankton
bloomed and cut off even
the canopy macrophytes
and their periphyton
Recovery of a Tidal Freshwater
Embayment from Eutrophication:
A Long-Term Study
R. Christian Jones
Department of Environmental Science and Policy
Potomac Environmental Research and Education Center
George Mason University
Fairfax, Virginia, USA
Tidal Potomac
River
• Part of the
Chesapeake Bay
tidal system
• Salinity zones
– Tidal Freshwater
(tidal river) <0.5
ppt
– Oligohaline
(transition zone)
0.5-6 ppt
– Mesohaline
(estuary) 6-14
ppt
Tidal Freshwater
Potomac
• Tidal freshwater
Potomac consists of
deep channel, shallower
flanks, and much
shallower embayments
• Being a heavily
urbanized area (about 4
million people),
numerous sewage
treatment plants
discharge effluent
• Note Blue Plains and
Lower Potomac
• Study area is Gunston
Cove located about 2/3
down the tidal fresh
section of the river
Historic Distribution
of Submersed
Macrophytes in the
Tidal Potomac
• According to maps and
early papers summarized by
Carter et al. (1985),
submersed macrophytes
occupied virtually all shallow
water habitat at the turn of
the 20th century
• Gunston Cove was
included
P Loading and Cyanobacterial Blooms
Point Source P Loading to
the Tidal Potomac
(kg/day)
1968
32,200
1978
7,700
1984
400
• Fueled by nutrient inputs
from a burgeoning human
population and resulting
increases in P inputs,
phytoplankton took over as
dominant primary
producers by about 1930.
• By the 1960’s large
blooms of cyanobacteria
were present over most of
the tidal freshwater
Potomac River during late
summer months
Macrophyte
Distribution in 1980
• Anecdotal records
indicate that by 1939,
submersed macrophytes
had declined strongly and
disappeared from much of
their original habitat
• An outbreak of water
chestnut (floating
macrophyte) was
observed in the 1940’s
• Surveys done in 1978-81
indicate only very sparse
and widely scattered beds
• Note no submersed
macrophytes were found
in Gunston Cove
Efforts to Clean up the River
• A major national and
multistate effort was initiated
to clean up the “nation’s
river”
• This paper describes the
response of one portion of
the tidal Potomac – Gunston
Cove to this major initiative
“The river, rich in history and memory,
which flows by our Nation’s capital should
serve as a model of scenic and
recreational values for the entire country”
President Lyndon B. Johnson - 1965
Point Source P Loading to
the Tidal Potomac
(kg/day)
1968
32,200
1978
7,700
1984
400
Tributary Watershed of Gunston Cove
Watershed
Statistics
Population: 330,911
Pop’n Density:
1362/km2 or 5.5/acre
Area: 94 mi2 or 243 km2
39% developed
9% agriculture
42% forest
Noman Cole Pollution
Control Plant
-Near the mouth of
Pohick Creek
-42 MGD (2004 avg)
-began operation 1970
P Loading Factors - Gunston Cove Watershed
400
350
300
120000
Watershed Households
250
Point Source Flow (m3x103)
100000
Point Source P Load (Kg)
200
80000
150
60000
100
40000
50
Year
20 03
20 01
19 99
19 97
19 95
19 93
19 91
19 89
19 87
19 85
19 83
19 81
19 79
0
19 77
20000
19 75
Watershed Households
140000
Daily Point Source P Load and Flow
160000
Households in the
Gunston Cove
watershed have grown
dramatically since the
mid-1970’s. Since the
study began in 1984
the number of
households has grown
by about 50%. All other
things equal, an
increase in households
should produce an
increase in nonpoint
contributions.
The point source P
load declined
dramatically in the late
1970’s and early
1980’s.
Formal study initiated
in 1983.
Since 1983/84,
water quality,
plankton, fish and
benthos have been
monitor-ed on a
generally
semimonthly basis
at a number of sites
in the Gunston
Cove area.
Monitoring
Site Key:
● water quality
and plankton
▲fish trawl
■ fish seine
Water Quality and Submersed
Macrophyte Variables
• Water Quality Variables
–
–
–
–
–
–
–
–
–
–
–
–
Temperature
Conductivity
Dissolved oxygen
pH
N: NO3-, NH4+, organic N
P: PO4-3, Part. P,Total P
BOD
TSS, VSS
Chloride
Alkalinity
Chlorophyll a
Secchi depth
• Submersed Macrophytes
– 1994-2006
• Areal coverage using
aircraft remote sensing
• Data collected by Virginia
Institute for Marine
Studies for the
Chesapeake Bay program
– Pre 1994
• USGS field surveys:
• GMU field surveys:
Water Quality Data Analysis
• Summer data (June-September) utilized
• Utilized one cove station (Station 7) that has been
sampled continuously over the period 1983-2006
• Scatterplot by year over the study period
• LOWESS smoothing function applied
• Linear trends also tested over the study period
• Regression coefficients determined for significant
linear trends
• Pre-1983 data were examined to place current study
in context
Gunston Cove Station
Total Phosphorus
Station 7: June-Sept
Total Phosphorus (mg/L)
1.00
0.10
1980
1990
2000
Year
2010
• P is limiting nutrient in this
system
• Summer total phosphorus
showed little change from
1983 through 1988
• Summer total phosphorus
decreased consistently from
1989 through 2006
• Linear trend highly significant
with a slope of -0.0044 mg/L
per yr or 0.10 mg/L over the
period of record.
• P load decrease was
complete by early 1980s. Yet
TP decrease doesn’t seem to
start until 1990? Or was the
1983-88 period just a pause
in a decline in TP that started
earlier?
Gunston Cove Station
Chlorophyll a
Chlorophyll a, Depth-integrated (ug/L)
Station 7: June - Sept
100
10
1980
1990
2000
Year
• Chlorophyll a levels have
decreased substantially over
the period.
• In the mid to late 1980’s
chlorophyll a frequently
exceeded 100 ug/L.
• Decline started in 1990 and
quickened after 2000
• By 2006 values were generally
less than 30 ug/L with a
median of about 20.
• Linear regression yielded a
significant linear decline at a
rate of -3.8 ug/L per year or 84
ug/L over the entire study
• Again, did the chlorophyll
decline start in 1990 or was
2010
this only part of a longer
chlorophyll decline?
Gunston Cove Station
TP – Extended Record
TP
1.000
0.100
0.010
1960
1970
1980 1990
YR
2000
2010
• Limited data from 1969/70
indicates that TP was much
higher at that time
• So, perhaps what appeared
to be a lag or delayed
response was actually just a
pause in the loading-induced
TP decline
• The pause was associated
with high pH induced internal
loading
• Total decline was from 0.8
mg/L to 0.06 mg/L over 36 yrs
or 0.02 mg/L/yr
Gunston Cove Station
Chlorophyll a – Extended Record
CHLA
1000
100
10
1960
1970
1980 1990
YR
2000
2010
• In contrast to the TP and
SRP, values of chlorophyll a
from 1969/70 were not
substantially higher than in
the early 1980’s
• This suggests that P levels
had to be drawn down to at
least the early 1980’s levels
(c. 0.15 mg/L) before
nutrient limitation of
phytoplankton could begin
to be a factor
• By 2000, TP was at about
0.10 mg/L and as it dropped
further it began to cause a
clear drop in chlorophyll a
TP response to decreased P
Loading?
• Rate of TP
decline was slow
during 1980’s
period of internal
loading
• Rate quickened
in 1990 with
apparent
cessation of
internal loading
Chla response to decreased TP in
water column?
• Adding in historic
data shows that
before P loading
reductions,
chlorophyll was not
sensitive to P in
water column
• Presumably it was
saturated with P, but
by 1983, P and Chl
were pretty closely
related.
• Even with
reductions, TP had
to drop below 0.2
mg/L, then Chl
started to decline
proportionately
Gunston Cove Light Environment
• Full restoration of Gunston Cove requires
re-establishment of submersed
macrophyte beds
• The primary requirement for this is light
availability throughout the water column
• Light attenuation is due to algae, inorganic
particles, and dissolved substances
Gunston Cove Station
Station 7: June - Sept
100
Secchi Disk Depth (cm)
90
80
70
60
50
40
30
20
10
1980
1990
2000
Year
2010
• Secchi disk was fairly
constant from 1984
through 1995 with the
trend line at about 40 cm.
• Since 1995 there has
been a steady increase in
the trend line from 40 cm
to nearly 80 cm in 2003.
• Linear regression was
highly significant with a
predicted increase of 1.51
cm per year or a total of
33 cm over the long term
study period
Predicted Maximum Macrophyte Depth (m)
Gunston Cove Light Environment
over time
• Using the two time
series of Kd, maximum
depth of macrophyte
colonization was
predicted using the 10%
surface light criterion
• Predicted maximum
macrophyte depth was
well below 1 m during
the 1980’s and 1990’s
• But beginning in about
2000 it started to rise
consistently and passed
1 m by 2003/04
2.0
1.5
1.0
0.5
0.0
1980
1990
2000
Year
2010
ZSAV10PERKSD
Secchi-disk approx.
ZSAV10PERK
Measured Kd
Reemergence of Submersed
Macrophytes in Gunston Cove
• 1987 Distribution
Reemergence of Submersed
Macrophytes in Gunston Cove
• 1995 Distribution
Reemergence of Submersed
Macrophytes in Gunston Cove
• 2000 Distribution
Reemergence of Submersed
Macrophytes in Gunston Cove
• 2005 Distribution
Summary of Phytoplankton, Light,
Submersed Macrophyte Response
200
SAV Coverage
Secchi Depth
Chlorophyll a
150
100
50
0
90
80
70
60
50
40
30
20
10
0
Secchi Depth (cm)
at Sta 7
250
19 9
4
19 9
5
19 9
6
19 9
7
19 9
8
19 9
9
20 0
0
20 0
1
20 0
2
20 0
3
20 0
4
20 0
5
20 0
6
Inner Cove SAV (ha) &
Chl a (ug/L) at Sta 7
Inner Cove SAV Coverage
vs. Secchi and Chlorophyll
• Improvements in
water clarity related to
P-limitation and
decline of
phytoplankton were
correlated with an
increase in submersed
macrophyte coverage
in Gunston Cove
• Since 1 m colonization
depth was achieved
(2004), macrophyte
coverage has
increased strongly
We have documented
the partial restoration of
Gunston Cove to its
pre-eutrophication
conditions including:
-Decrease in P loading
-Decrease in TP and
phytoplankton
chlorophyll
-Increase in water
clarity
-Reestablishment of
submersed macrophyte
beds to a substantial
portion of the cove