EVPP%20550%20Waterscape%20Ecology%20and%20Management%20

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EVPP 550Waterscape Ecology and Management
Lecture 11

• Professor
• R. Christian Jones
• Fall 2007

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Lake Biology FishMajor Freshwater Groups
Brook Trout native to E. US

• Salmonidae
• Trout and salmon
• Distribution
• Clear, cool waters
• Rivers streams moderate to swift
• Lakes cool well oxygenated
• Food sources
• Aquatic insects
• Small fishes

Rainbow Trout native to W. US
Lake Whitefish native to Gt. Lakes other
northern lakes
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Lake Biology FishMajor Freshwater Groups
Northern Pike native to E. US

• Esocidae
• 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
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Lake Biology FishMajor Freshwater Groups
Blacknose dace very common native

• Cyprinidae
• Minnows, chubs, dace, shiners
• Most are small
• Distribution
• Widespread in both lakes and stream
• Food supply
• Aquatic insects
• Small crustacea
• Oligochaetes

Creek chub common creek forage fish
Golden shiner native forage fish
Common carp native of Eurasia can get large
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Lake Biology FishMajor Freshwater Groups

• Catostomadae
• Suckers
• Distribution
• Widespread in lakes and streams
• Food supply
• Aquatic insects
• Small crustacea
• Oligochaetes
• Periphyton

Northern hogsucker creek fish that eats
periphyton
Silver redhorse
White sucker common and tolerant creek fish
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Lake Biology FishMajor Freshwater Groups

• Ictaluridae
• Catfish, bullheads
• Distribution
• Slow-moving still waters often with muddy bottoms
• Food supply
• Aquatic insects
• Oligochaetes
• Benthic items

Margined madtom very small creek fish
Black bullhead common in Potomac
Channel Catfish native to S. US can get 20 lb
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Lake Biology FishMajor Freshwater Groups
Bluegill sunfish

• Centrarchidae
• Sunfish, bass, crappie
• Distribution
• Widespread, tendency to warmer waters
• Food supply
• Aquatic insects
• Crustacea
• Molluscs
• Fish (in large individuals)

Pumpkinseed sunfish common in ponds and lakes
Largemouth bass common piscivore in lakes and
ponds
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Lake Biology FishMajor Freshwater Groups

• Percidae
• Perches, darters
• Distribution
• Widespread
• Food supply
• Aquatic insects
• Crustacea
• Molluscs
• Fish in larger individuals

Tesselated darter small creek and lake species
                                                
                   ltgt
Yellow perch common early spring spawner
Walleye large lake and river species
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Lake Biology FishGlobal Distribution
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Lake Biology FishGlobal Distribution
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Lake Biology FishTrophic 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)

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Lake Biology FishTrophic 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

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Lake Biology FishTrophic Roles

• Piscivores
• Feed on other fishes
• Often will eat young of their own species
• Largemouth smallmouth bass
• Muskellunge

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Lake Biology FishLife 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

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Lake Biology FishLife 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?
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Lake Biology FishFactors affecting growth

• Temperature
• Has a strong effect on growth rate and feeding
  rate
• Cold water species reach maximum growth rates at
  lower temperature

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Lake Biology FishFactors 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
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Lake Biology FishFactors 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
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Lake Biology FishFactors 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
Stomachs
Environment
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Lake Biology FishFactors 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
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Lake Biology FishPatterns of Abundance
Production

• Resource Habitat Partitioning
• Partitioning is thought to have evolved to
  minimize competition

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Lake Biology FishPatterns of Abundance
Production

• Habitat Selection
• Many fish prefer vegetation and collections are
  often greater at night

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Lake Biology FishPatterns 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

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Lake Biology FishPatterns 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

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Lake Biology FishPatterns of Abundance
Production

• Effect of Bottom Up Processes
• The same trend but with a different slope has
  been found in other systems

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Lake Biology FishPatterns 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

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Lake Biology FishPatterns of Abundance
Production

• Top Down Processes
• The imporance of top-down processes is emphasized
  by the Trophic Cascade model

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Management of Freshwater Systems

• Freshwater is a valuable resource for
• Drinking water
• Living resources
• Food supplies
• Irrigation
• Transportation
• Other

• Its use may be impaired by pollutants
• Decomposable organics (BOD)
• Excess nutrients
• Acidification
• Toxic chemicals
• Hormones
• Erosion and Sedimentation
• Salinization
• Other

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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

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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

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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 NP
• Basically, you try to move what would happen in
  nature into a controlled setting that doesnt
  impact the natural environment

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Excess Nutrients NPNatural 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

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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

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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

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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

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Cultural Eutrophication Case Studies

• Lake Washington
• Following WWII, popn 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 1960s
• Algae subsided and water clarity increase
• Daphnia reestablished itself and further
  clarified the lake

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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

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Recovery of a Tidal Freshwater Embayment from
EutrophicationA Long-Term Study

• R. Christian Jones
• Department of Environmental Science and Policy
• Potomac Environmental Research and Education
  Center
• George Mason University
• Fairfax, Virginia, USA

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Tidal Potomac River

• Part of the Chesapeake Bay tidal system
• Salinity zones
• Tidal Freshwater (tidal river) lt0.5 ppt
• Oligohaline (transition zone) 0.5-6 ppt
• Mesohaline (estuary) 6-14 ppt

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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

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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

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P Loading and Cyanobacterial Blooms

• 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 1960s large blooms of cyanobacteria were
  present over most of the tidal freshwater Potomac
  River during late summer months

• Point Source P Loading to the Tidal Potomac
  (kg/day)
• 32,200
• 7,700
• 1984 400

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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 1940s
• Surveys done in 1978-81 indicate only very sparse
  and widely scattered beds
• Note no submersed macrophytes were found in
  Gunston Cove

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Efforts to Clean up the River

• A major national and multistate effort was
  initiated to clean up the nations river
• This paper describes the response of one portion
  of the tidal Potomac Gunston Cove to this major
  initiative

• Point Source P Loading to the Tidal Potomac
  (kg/day)
• 32,200
• 7,700
• 1984 400

The river, rich in history and memory, which
flows by our Nations capital should serve as a
model of scenic and recreational values for the
entire country President Lyndon B. Johnson - 1965
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Tributary Watershed of Gunston Cove
Watershed Statistics Population 330,911 Popn
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
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Households in the Gunston Cove watershed have
grown dramatically since the mid-1970s. 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
1970s and early 1980s. Formal study initiated
in 1983.
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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.
Noman Cole PCP
Monitoring Site Key ? water quality and
plankton ?fish trawl fish seine
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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

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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

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Gunston Cove StationTotal Phosphorus

• 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 doesnt seem to start until 1990? Or
  was the 1983-88 period just a pause in a decline
  in TP that started earlier?

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Gunston Cove StationChlorophyll a

• Chlorophyll a levels have decreased substantially
  over the period.
• In the mid to late 1980s 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 this only part of a longer chlorophyll
  decline?

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Gunston Cove StationTP Extended Record

• 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

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Gunston Cove StationChlorophyll a Extended
Record

• In contrast to the TP and SRP, values of
  chlorophyll a from 1969/70 were not substantially
  higher than in the early 1980s
• This suggests that P levels had to be drawn down
  to at least the early 1980s 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

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TP response to decreased P Loading?

• Rate of TP decline was slow during 1980s period
  of internal loading
• Rate quickened in 1990 with apparent cessation of
  internal loading

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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

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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

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Gunston Cove Station

• 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

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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 1980s and 1990s
• But beginning in about 2000 it started to rise
  consistently and passed 1 m by 2003/04

Secchi-disk approx. Measured Kd
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Reemergence of Submersed Macrophytes in Gunston
Cove

• 1987 Distribution

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Reemergence of Submersed Macrophytes in Gunston
Cove

• 1995 Distribution

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Reemergence of Submersed Macrophytes in Gunston
Cove

• 2000 Distribution

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Reemergence of Submersed Macrophytes in Gunston
Cove

• 2005 Distribution

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Summary of Phytoplankton, Light, Submersed
Macrophyte Response

• 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

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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