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Spatial and Temporal Variation in Mercury Bioaccumulation by Zooplankton in Lake Champlain

Spatial and Temporal Variation in Mercury Bioaccumulation by Zooplankton in Lake Champlain. Celia Chen 1 , Neil Kamman 2 , Jason Williams 3 , Deenie Bugge 1 , Vivien Taylor 1 , Brian Jackson 1 , and Eric Miller 4 1. Dartmouth College, 2. VT Dept. of Environmental Conservation,

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Spatial and Temporal Variation in Mercury Bioaccumulation by Zooplankton in Lake Champlain

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  1. Spatial and Temporal Variation in Mercury Bioaccumulation by Zooplankton in Lake Champlain Celia Chen1, Neil Kamman2, Jason Williams3, Deenie Bugge1, Vivien Taylor1, Brian Jackson1, and Eric Miller4 1. Dartmouth College, 2. VT Dept. of Environmental Conservation, 3. TerraGraphics Inc., 4. Environmental Resources Group, Ltd.

  2. Factors Controlling Hg Bioaccumulation and Trophic Transfer • Oligotrophic lakes have higher Hg in fish than eutrophic lakes. • Higher zooplankton densities related to lower Hg concentrations in fish. • High plankton biomass biodilutes the MeHg that is bioaccumulated and transferred. • High densities of algal cells accumulate less total Hg and MeHg (biodilution) • Zooplankton consuming these algae in accumulate less total Hg and MeHg (trophic dilution)

  3. Research Questions • Spatial variation of Hg bioaccumulation in food webs between basins in a single lake. • Year-to-year variation in Hg bioaccumulation within and between individual basins. • Seasonal variation in Hg bioaccumulation in plankton within and between individual basins. • Methods • Sampled multiple basins in 2005-2009 • Collected Zooplankton samples (45-202 µm - small, >202 µm – large) and fish samples • Measured Hg speciation with cold vapor ICP-MS (Dartmouth TEA Core facility)

  4. Basin trophic status varies in Lake Champlain Total P Malletts - oligotrophic (8-12 µg/L) Missisquoi - eutrophic (35-70 µg/L) with annual algal blooms Prediction: Hg bioaccumulation in Malletts>Missisquoi n

  5. Spatial Variation in Zooplankton and Fish Lake Champlain Basin Program

  6. Basin and Interannual Differences in Zooplankton Hg and MeHg Across Years Total Hg p = 0.0185 p = 0.0004 p = 0.0019 MAL MIS MAL MIS MAL MIS MeHg p < 0.0001 p = 0.5939 p < 0.0001 MAL MIS MAL MIS MAL MIS 2005 2006 2007

  7. MIS eutrophic Spatial Variation in Hg Across All Basins (2009) MAL oligotrophic OTC mesotrophic ng/g ng/g

  8. Malletts • Seasonal Variation in • Zooplankton MeHg • MeHg in Malletts more than 3X higher than Missisquoi • Smaller zooplankton in Malletts have low MeHg. • Malletts has later peak in MeHg. • MeHg decreases in zooplankton in late summer. Missisquoi 2008 Data

  9. Seasonal Variation in Zooplankton %MeHg • %MeHg is similar in two basins. • %MeHg increases in mid-summer in both basins. • Seasonal change is greater in >202 µm zooplankton. Malletts Missisquoi

  10. What about Hg and MeHg in fish? Littoral Zone Fish Pelagic Zone Fish 2009 2005 p = 0.7963 Total Hg ppm 2006 p = 0.7012 2009 fish samples, VT Fish and Game

  11. Conclusions • Spatial Variation:Malletts Bay has lower chlorophyll concentrations and higher Hg and MeHg in zooplankton than Missisquoi • Higher Hg bioaccumulation in more oligotrophic basin • Higher Hg burdens in Malletts Bay zooplankton correspond to higher concentrations in pelagic fish (not littoral zone fish). • Interannual Variation: THg and MeHg concentrations in zooplankton vary year to year. • 2007 was an unusual year in Missisquoi (no algal bloom)and differences in zooplankton MeHg disappeared. • Seasonal Variation: Temporal patterns in both sites suggest declines in MeHg in fall and higher %MeHg in zooplankton in mid-summer.

  12. Acknowledgments Collaborators Jamie Shanley and Ann Chalmers, USGS Brandon Mayes, Long Trail Brewing Co. Tom Holsen, Clarkson Univ. Technical Assistance Pete Stangel and Angela Shamaugh (Vermont DEC); Chip Glaholt (Indiana Univ.); Elizabeth Traver (Dartmouth College); Lydia Smith (Univ. of VT); Bernie Pientka (VT Fish and Game) This research is supported by NOAA through the Lake Champlain Research Consortium and NIEHS as part of a Superfund Research Program at Dartmouth College.

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