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Hypoxia in Lake Erie:

INFLUENCE OF HYPOXIA ON THE ECOLOGY OF ZOOPLANKTIVOROUS AND BENTHIVOROUS FISHES IN LAKE ERIE’S CENTRAL BASIN. T.O. Höök 1,2,* , S.A. Ludsin 2 , S.A. Pothoven 3 , J.J. Roberts 1,2 , T.F. Nalepa 2 , H.A. Vanderploeg 2 , S.A. Ruberg 2 , and S.B. Brandt 2 .

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Hypoxia in Lake Erie:

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  1. INFLUENCE OF HYPOXIA ON THE ECOLOGY OF ZOOPLANKTIVOROUS AND BENTHIVOROUS FISHES IN LAKE ERIE’S CENTRAL BASIN. T.O. Höök1,2,*, S.A. Ludsin2, S.A. Pothoven3, J.J. Roberts1,2 , T.F. Nalepa2, H.A. Vanderploeg2, S.A. Ruberg2, and S.B. Brandt2. 1Cooperative Institute for Limnology and Ecosystems Research, University of Michigan, Ann Arbor, MI. 2National Oceanic and Atmospheric Administration, Great Lakes Environmental Research Laboratory, Ann Arbor, MI. 3National Oceanic and Atmospheric Administration, Great Lakes Environmental Research Laboratory, Muskegon, MI. *(thook@umich.edu)

  2. East Central Low oxygen West Warm epilimnion Cool hypolimnion (becomes hypoxic) Cool Source: Murray Charlton, NWRI Hypoxia in Lake Erie: Natural phenomenon -Modified by various factors (e.g., nutrients, climate, water levels)

  3. Effects of Hypoxia on Yellow Perch and Rainbow Smelt $ Recreational Fisheries $ Walleye $ Commercial Fisheries $ Yellow perch Rainbow smelt Most abundant species in L. Erie’s central basin. Benthic invertebrates Zooplankton

  4. Effects of Hypoxia on Yellow Perch and Rainbow Smelt Day Night Diel vertical migrations thermocline thermocline Yellow perch Rainbow smelt Hypoxia may alter: -Distributions -Diets -Growth/Condition Omnivory Benthic invertebrates Zooplankton

  5. 24-hr paired-vessel sampling • Zooplankton • Temperature • Dissolved oxygen • Light levels • Chlorophyll a Fish Biomass -Zooplankton net and pump sampling -Ponar grabs (benthos) -Midwater and bottom trawling

  6. 2005 D C 5km diel station A B F D B H Depth (m) Depth (m) Site B A B Site B H 0 4 8 12 (mg/l) June October August September September

  7. Effects of Hypoxia in Lake Erie. Strength of evidence • Distributions of perch and smelt. • Diets of perch and smelt. • Condition/Growth of perch and smelt. high low All data from Station B

  8. Vertical Distributions of Yellow Perch and Rainbow Smelt Night Day High Depth (m) High

  9. Vertical Distributions of Yellow Perch and Rainbow Smelt Hypoxic Low Low Night Day Depth (m) High High

  10. Vertical Distributions of Yellow Perch and Rainbow Smelt Hypoxic Low Low Night Day High High High High

  11. Vertical Distributions of Yellow Perch and Rainbow Smelt Yellow perch ln(cpue+1) Sep (hypoxia) Oct June Aug Rainbow smelt

  12. Diets of Yellow Perch and Rainbow Smelt Zooplankton Benthic Invertebrates Chironomid Pupae Yellow perch Sep (hypoxia) Oct June Aug Diet (% of diet items) Rainbow smelt

  13. Diets of Yellow Perch and Rainbow Smelt Yellow perch a a a a Sep (hypoxia) Oct June Aug Dry weight of stomach contents (g g-1) a b Rainbow smelt c c

  14. Cumulative effects on condition and growth Yellow perch a b b b % Dry/Wet weight Sep (hypoxia) Oct June Aug a b c d Rainbow smelt

  15. Quantifying Growth and Condition Traditional measures of growth and condition. -Integrate feeding history and energetic utilization over the whole life-time of an organism. RNA:DNA Ratios -DNA concentrations within cells remain fairly constant. -RNA concentrations increase as protein synthesis increases. -A recently well-fed, growing individual should have a high RNA:DNA ratio compared to a starving individual.

  16. Instantaneous effects on growth a Yellow perch ab no data b RNA:DNA (liver) Sep (hypoxia) Oct June Aug a a a no data Rainbow smelt

  17. Instantaneous effects on growth a a a Yellow perch no data RNA:DNA (muscle) Sep (hypoxia) Oct June Aug a a b no data Rainbow smelt

  18. Effects of Hypoxia in Lake Erie. high • Distributions of perch and smelt. • Lower overall catches during hypoxia. • Avoid bottom waters during hypoxia. • Diets of perch and smelt. • ↑Zooplankton; ↓Benthic invertebrates • Ration may be affected • Seasonal patterns may mask hypoxia effects • Condition/Growth of perch and smelt. • Potential cumulative and instantaneous growth effects • Seasonal patterns may mask hypoxia effects Strength of evidence low

  19. Zoopl. vulnerability and individual growth may increase. Daphnia mendotae (preliminary data) Daytime August June August September RNA:DNA September Length (mm) Preliminary RNA:DNA patterns for Daphnia mendotae collected (via whole water column tows) in central Lake Erie during 2005.

  20. Does hypoxia affect production of L. Erie fishes?? Next Steps • 2007 Field sampling. • Focus on spatial patterns. • Experimental evaluations of yellow perch and walleye growth. • Modeling analyses (EcoFore Project). • Statistical analyses, GRP, IBM, CASM, EcoPath/EcoSim

  21. Ecological Consequences of Hypoxia in Lake Erie: Piscivorous Fish Invertivorous Fish International Field Year in Lake Erie (2005)www.glerl.noaa.gov/ifyle NOAA-GLERL led effort to understand the causes and ecological consequences of seasonal hypoxia in Lake Erie. Benthic invertebrates Zooplankton Phytoplankton Microbes Nutrients Physical Processes

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