Spatial and Temporal Variation Spatial and Temporal Variation in Mercury Bioaccumulation by in Mercury Bioaccumulation by

Zooplankton in Lake Zooplankton in Lake ChamplainChamplain

Celia ChenCelia Chen11, Neil Kamman, Neil Kamman22, Jason Williams, Jason Williams33, Deenie , Deenie BuggeBugge11, Vivien Taylor, Vivien Taylor11, Brian Jackson, Brian Jackson11, and Eric Miller, and Eric Miller44

1. Dartmouth College, 2. VT Dept. of Environmental Conservation, 1. Dartmouth College, 2. VT Dept. of Environmental Conservation,

3. TerraGraphics Inc., 4. Environmental Resources Group, Ltd. 3. TerraGraphics Inc., 4. Environmental Resources Group, Ltd.

Factors Controlling Hg Bioaccumulation Factors Controlling Hg Bioaccumulation and Trophic Transferand Trophic Transfer

Oligotrophic lakes have higher Hg in fish Oligotrophic lakes have higher Hg in fish than eutrophic lakes.than eutrophic lakes.

Higher zooplankton densities related to Higher zooplankton densities related to lower Hg concentrations in fish.lower Hg concentrations in fish.

High plankton biomass biodilutes the MeHg High plankton biomass biodilutes the MeHg that is bioaccumulated and transferred.that is bioaccumulated and transferred.

High densities of algal cells accumulate High densities of algal cells accumulate less total Hg and MeHg (biodilution)less total Hg and MeHg (biodilution)

Zooplankton consuming these algae in Zooplankton consuming these algae in accumulate less total Hg and MeHg accumulate less total Hg and MeHg (trophic dilution)(trophic dilution)

Research QuestionsResearch Questions Spatial variation Spatial variation of Hg bioaccumulation in food of Hg bioaccumulation in food

webs between basins in a single lake. webs between basins in a single lake. Year-to-year variation Year-to-year variation in Hg bioaccumulation in Hg bioaccumulation

within and between individual basins.within and between individual basins. Seasonal variation Seasonal variation in Hg bioaccumulation in in Hg bioaccumulation in

plankton within and between individual basins.plankton within and between individual basins.

MethodsMethods Sampled multiple basins in 2005-2009Sampled multiple basins in 2005-2009 Collected Zooplankton samples (45-202 µm - small, Collected Zooplankton samples (45-202 µm - small,

>202 µm – large) and fish samples>202 µm – large) and fish samples Measured Hg speciation with cold vapor ICP-MS Measured Hg speciation with cold vapor ICP-MS

(Dartmouth TEA Core facility)(Dartmouth TEA Core facility)

Basin trophic status varies in Lake Basin trophic status varies in Lake ChamplainChamplain

Total PTotal P

Malletts - oligotrophic Malletts - oligotrophic

(8-12 µg/L)(8-12 µg/L)

Missisquoi - Missisquoi - eutrophic (35-70 µg/L)eutrophic (35-70 µg/L)

with annual algal bloomswith annual algal blooms

Prediction: Hg Prediction: Hg bioaccumulation in bioaccumulation in Malletts>MissisquoiMalletts>Missisquoi

n

Lake Champlain Basin Program

Spatial Variation in Zooplankton and FishSpatial Variation in Zooplankton and Fish

Basin and Interannual Differences in Basin and Interannual Differences in Zooplankton Hg and MeHg Across YearsZooplankton Hg and MeHg Across Years

2007 THg (ug/g DW)

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

Mallet's Bay Missisquoi Bay

20052005 20062006 20072007

Total HgTotal Hg

MeHgMeHg

p = 0.0019

2005 THg (ug/g DW)

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

Mallet's Bay Missisquoi Bay

p = 0.0185

2006 THg (ug/g DW)

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

Mallet's Bay Missisquoi Bay

p = 0.0004

2005 MeHg (ug/g DW)

0

0.01

0.02

0.03

0.04

0.05

Mallet's Bay Missisquoi Bay

p < 0.0001

2006 MeHg (ug/g DW)

0

0.01

0.02

0.03

0.04

0.05

Mallet's Bay Missisquoi Bay

p < 0.0001

2007 MeHg (ug/g DW)

0

0.01

0.02

0.03

0.04

0.05

Mallet's Bay Missisquoi Bay

p = 0.5939

MIS MIS MIS

MIS MIS MIS

MAL MAL MAL

MAL MAL MAL

Spatial Variation in Hg Spatial Variation in Hg Across All Basins (2009)Across All Basins (2009)

MISeutrophic

MALoligotrophic

OTCmesotrophic

ng/gng/g

Seasonal Variation inSeasonal Variation inZooplankton MeHgZooplankton MeHg

MeHg in Malletts more MeHg in Malletts more than 3X higher than than 3X higher than MissisquoiMissisquoi

Smaller zooplankton in Smaller zooplankton in Malletts have low MeHg.Malletts have low MeHg.

Malletts has later peak Malletts has later peak in MeHg. in MeHg.

MeHg decreases in MeHg decreases in zooplankton in late zooplankton in late summer.summer.

Malletts

Missisquoi

2008 Data2008 Data

Seasonal Variation Seasonal Variation in Zooplankton in Zooplankton %MeHg%MeHg

%MeHg is similar in %MeHg is similar in two basins.two basins.

%MeHg increases %MeHg increases in mid-summer in in mid-summer in both basins.both basins.

Seasonal change is Seasonal change is greater in >202 µm greater in >202 µm zooplankton.zooplankton.

Missisquoi

Malletts

What about Hg and MeHg in fish?

2009 fish samples, VT Fish and Game2009 fish samples, VT Fish and Game

Total Hg Concentration (ug/g WW)

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

MALL MISS OTTE

Site

20052005p = 0.7963

20092009

Littoral Zone FishLittoral Zone Fish Pelagic Zone FishPelagic Zone Fish

20062006p = 0.7012

To

tal

Hg

pp

m

ConclusionsConclusions Spatial Variation:Spatial Variation: Malletts Bay has lower chlorophyll Malletts Bay has lower chlorophyll

concentrations and higher Hg and MeHg in zooplankton concentrations and higher Hg and MeHg in zooplankton than Missisquoithan Missisquoi Higher Hg bioaccumulation in more oligotrophic basinHigher Hg bioaccumulation in more oligotrophic basin Higher Hg burdens in Malletts Bay zooplankton correspond to Higher Hg burdens in Malletts Bay zooplankton correspond to

higher concentrations in pelagic fish (not littoral zone fish).higher concentrations in pelagic fish (not littoral zone fish).

Interannual Variation: Interannual Variation: THg and MeHg concentrations in THg and MeHg concentrations in zooplankton vary year to year.zooplankton vary year to year. 2007 was an unusual year in Missisquoi (no algal bloom)and 2007 was an unusual year in Missisquoi (no algal bloom)and

differences in zooplankton MeHg disappeared.differences in zooplankton MeHg disappeared.

Seasonal Variation: Seasonal Variation: Temporal patterns in both sites Temporal patterns in both sites suggest declines in MeHg in fall and higher %MeHg in suggest declines in MeHg in fall and higher %MeHg in zooplankton in mid-summer.zooplankton in mid-summer.

AcknowledgmentsAcknowledgmentsCollaboratorsCollaborators

Jamie Shanley and Ann Chalmers, USGSJamie Shanley and Ann Chalmers, USGSBrandon Mayes, Long Trail Brewing Co.Brandon Mayes, Long Trail Brewing Co.

Tom Holsen, Clarkson Univ. Tom Holsen, Clarkson Univ.

Technical AssistanceTechnical AssistancePete Stangel and Angela Shamaugh Pete Stangel and Angela Shamaugh

(Vermont DEC); Chip Glaholt (Indiana (Vermont DEC); Chip Glaholt (Indiana Univ.); Elizabeth Traver (Dartmouth Univ.); Elizabeth Traver (Dartmouth College); Lydia Smith (Univ. of VT); College); Lydia Smith (Univ. of VT); Bernie Pientka (VT Fish and Game)Bernie Pientka (VT Fish and Game)

This research is supported by NOAA This research is supported by NOAA through the Lake Champlain Research through the Lake Champlain Research

Consortium and NIEHS as part of a Consortium and NIEHS as part of a Superfund Research Program at Superfund Research Program at

Dartmouth College.Dartmouth College.