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EVPP 550 Waterscape Ecology and Management – Lecture 11

EVPP 550 Waterscape Ecology and Management – Lecture 11. Professor R. Christian Jones Fall 2007. Lake Biology – Fish Major Freshwater Groups. Brook Trout – native to E. US. Salmonidae Trout and salmon Distribution Clear, cool waters Rivers & streams: moderate to swift

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EVPP 550 Waterscape Ecology and Management – Lecture 11

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  1. EVPP 550Waterscape Ecology and Management – Lecture 11 Professor R. Christian Jones Fall 2007

  2. 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

  3. 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

  4. 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

  5. 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

  6. 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

  7. 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

  8. 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                                                                   <> Yellow perch – common early spring spawner Walleye – large lake and river species

  9. Lake Biology – FishGlobal Distribution

  10. Lake Biology – FishGlobal Distribution

  11. 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)

  12. 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

  13. Lake Biology – FishTrophic Roles • Piscivores • Feed on other fishes • Often will eat young of their own species • Largemouth & smallmouth bass • Muskellunge

  14. 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

  15. 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?

  16. 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

  17. 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

  18. 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

  19. 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

  20. 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

  21. Lake Biology – FishPatterns of Abundance & Production • Resource & Habitat Partitioning • Partitioning is thought to have evolved to minimize competition

  22. Lake Biology – FishPatterns of Abundance & Production • Habitat Selection • Many fish prefer vegetation and collections are often greater at night

  23. 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

  24. 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

  25. 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

  26. 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

  27. Lake Biology – FishPatterns of Abundance & Production • Top Down Processes • The imporance of top-down processes is emphasized by the Trophic Cascade model

  28. 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 of Freshwater Systems

  29. 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

  30. 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

  31. 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

  32. Excess Nutrients – N&PNatural 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

  33. 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

  34. 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

  35. 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

  36. 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

  37. 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

  38. 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

  39. 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

  40. 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

  41. 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

  42. P Loading and Cyanobacterial Blooms • Point Source P Loading to the Tidal Potomac (kg/day) • 32,200 • 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

  43. 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

  44. 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 • 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 Nation’s capital should serve as a model of scenic and recreational values for the entire country” President Lyndon B. Johnson - 1965

  45. 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

  46. 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.

  47. 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

  48. 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 and Submersed Macrophyte Variables

  49. 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 Water Quality Data Analysis

  50. 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 doesn’t 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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