Deposition & Cycling of Sulfur Control Mercury Accumulation in Isle Royale Fish. Paul Drevnick

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1 Deposition & Cycling of Sulfur Control Mercury Accumulation in Isle Royale Fish Paul Drevnick

2 Coauthors Don Canfield,, SDU Pat Gorski,, UW Avery Shinneman,, UMN Dan Engstrom,, SCWRS Derek Muir,, EC Jerry Smith, UMI Paul Garrison,, WDNR Lisa Cleckner,, UW Jim Hurley,, UW Bob Noble, Miami U Ryan Otter, Miami U Jim Oris,, Miami U Funding US EPA Miami U SETAC SOAS Data Sharing Larry Kallemeyn Tom Kelly Logistical Support National Park Service Laboratory Assistance Doug Nelson Lilian Salling Field Assistance Many volunteers

3 Hg is toxic to and through fish Hg is ubiquitous in the environment, but is mostly of concern as CH 3 Hg in fish CH 3 Hg is toxic to fish and wildlife/human consumers Fish consumption advisories for CH 3 Hg are common

4 Hg in lakes Methylation of Hg Biomagnification of CH 3 Hg High Hg T concentrations in fish Source: loer.tamug.tamu.edu

5 Isle Royale National Park Canada NADP/MDN Site ISRO United States

6 Isle Royale s inland lakes >40 lakes are renowned as pristine aquatic ecosystems Kallemeyn (2000) reported high Hg T concentrations in fish from several lakes Every effort should be made to protect the fish fauna of Isle Royale Source: U.S. National Park Service

7 Objective 1 Determine the toxicological effects of CH 3 Hg on fishes in inland lakes of Isle Royale National Park

8 Hg T (μg/g wet wt) in edible fillet of 55-cm northern pike SIS RIC INT SAR WAG ANG SHE EVA Lake

9 Objective 1 Determine the toxicological effects of CH 3 Hg on fishes in inland lakes of Isle Royale National Park Objective 2 Determine cause for CH 3 Hg decline in northern pike

10 Hypothesis 1 Atmospheric Hg deposition has declined, reducing the amount of Hg available for methylation Hypothesis 2 Changes in the ecology of northern pike and/or its underlying food web have occurred, reducing the bioaccumulation and/or biomagnification of methylmercury Hypothesis 3 Environmental factors that stimulate net methylation have lessened, reducing the amount of CH 3 Hg for bioaccumulation

11 Atmospheric Hg deposition has not declined 100 SIS RIC SAR WHI Hg T (μg/m 2 yr) accumulation in sediment Hg T (μg/m 2 yr) wet deposition 2.5 NADP/MDN Site Year

12 Changes in the ecology of northern pike have not occurred 16 RIC SAR Inferred Total P (μg/l) Year

13 Changes in the ecology of northern pike have not occurred Mean (1 SE) stable carbon (δ13c) and nitrogen (δ15n) isotope compositions in edible fillets of northern pike in lakes of Isle Royale Lake n δ 13 C (ä) δ 15 N (ä) n δ 13 C (ä) δ 15 N (ä) n δ 13 C (ä) δ 15 N (ä) n δ 13 C (ä) δ 15 N (ä) ANG (0.10) 8.47 (0.20) (0.22) 9.10 (0.15) EVA (0.51) 9.76 (0.30) (0.27) 9.73 (0.11) INT (0.77) 8.84 (0.11) (0.12) (0.12) RIC (0.36) 9.98 (0.19) (0.34) 9.99 (0.14) (0.25) 9.70 (0.28) SAR (na) 9.49 (na) (0.35) 9.80 (0.32) (0.17) (0.14) (0.14) (0.16) SHE (0.16) 8.17 (0.48) (0.11) 9.57 (0.08) SIS (na) 8.39 (na) (0.50) 8.48 (0.17) WAG (0.29) 8.28 (0.13) (0.40) 8.47 (0.12)

14 Changes in the ecology of northern pike have not occurred Mean back-calculated total length (cm) of northern pike in lakes of Isle Royale Kallemeyn (12); Age (Years) total length = a + b Ln(age) Lake Sex n a b r 2 ANG F M EVA F M INT F M RIC F M SAR F M SHE F M SIS F M WAG F M Drevnick et al.; Age (Years) total length = a + b Ln(age) Lake Sex n a b r 2 ANG F M EVA F M INT F M RIC F M SAR F M SHE F M SIS F M WAG F M

15 Environmental factors: SO4

16 Methylation of Hg is dependent on [SO 4 ] SO 4 addition experiments: Intact sediment cores Wetland mesocosms Whole lake Source: loer.tamug.tamu.edu

17 Sulfate Water Sediment? Sulfate reduction Sulfide Sulfide oxidation Sulfide complexation? Oxic Anoxic Inorganic mercury Methylmercury Inorganic mercury Methylmercury

18 SO 4 is a primary component of acid rain 2.0 Historic SO 4 deposition in the Great Lakes region Aherne et al. Water Air Soil Pollut. Focus 4, (2004) 1.5 SO 4 deposition (relative scale) Clean Air Act Industrial Revolution Year

19 12 NADP/MDN Site ISRO 9 SO 4 (kg/ha yr) wet deposition Year

20 SO 4 in inland lakes of Isle Royale National Park SO 4 concentration (μm) Lake AHM. 21 AMY ANG BEA. 34 BEN. 23 CHI DES DUS EPI EVA. 22 FEL. 33 FOR GEO HAL HAR. 28 HAT INT JOH LES. 30 LIN. 28 LIV MAS. 33 MCD. 35 NEW 34. OTT. 29 PAT. 12 RIC SAR. 34 SCH SHE. 18 SIS. 47 THE 27. WAG. 35 WHI

21 Hypothesis Declines in SO 4 deposition have inhibited SO 4 reduction, resulting in less methylation of Hg and thus less CH 3 Hg bioaccumulation into fish Hypothesis Test Reconstruct the history of SO 4 reduction by exploring sulfur concentrations in sediment profiles

22 Sedimentary Sulfur (mg/g dry wt) Clean Air Act Depth (cm) Industrial Revolution Total CRS Non-CRS 40 RIC SAR

23 Hypothesis CH 3 Hg bioaccumulation in fish primarily a function of SO 4 deposition and SO 4 reduction during past century Hypothesis Test Compare Hg T in fish to time-equivalent CRS in sediment

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26 SIS RIC SAR CRS (mg/g dry wt) in sediment Hg T (μg/g wet wt) in northern pike Year

27 WHI CRS (mg/g dry wt) in sediment Hg T (μg/g wet wt) in walleye Year

28 SIS CRS (mg/g dry wt) in sediment Hg T (μg/g wet wt) in coregonids Year

29 SO 4 deposition and SO 4 reduction control CH 3 Hg bioaccumulation in fish Log 10 (Hg T in fish) -0.8 r = 0.852, p < Log 10 (CRS in sediment)

30 CRS (mg/g dry wt) in sediment SIS RIC SAR WHI SO deposition and SO reduction control CH 3 Hg bioaccumulation in fish Year Hg T (μg/g wet wt) in northern pike (N), walleye (W), or Coregonus spp. (C) 0.0 Log 10 (Hg T in fish) Log 10 (CRS in sediment)

31 Conclusions Reductions in CH 3 Hg possible without reductions in Hg Reductions in CH 3 Hg possible with reductions in SO 4 To solve Hg problem in SO 4 -limited lakes: Local: Don t unnecessarily add SO 4 (e.g., CuSO 4 )

32 Houghton Lake, MI: CuSO 4 additions S accumulation (g/m 2 yr) in sediment Year

33 Conclusions Reductions in CH 3 Hg possible without reductions in Hg Reductions in CH 3 Hg possible with reductions in SO 4 To solve Hg problem in SO 4 -limited lakes: Local: Don t unnecessarily add SO 4 (e.g., CuSO 4 ) Regional: Continue existing acid rain programs Global: Don t add SO 2 to atmosphere to slow climate change

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