Whole-ecosystem study shows rapid fish-mercury response to changes in mercury deposition

^aTetra Tech Inc., 180 Forestwood Drive, Oakville, ON, Canada L6J 4E6;
^cR&K Research Inc., 675 Mt. Belcher Heights, Salt Spring Island, BC, Canada V8K 2J3;
^dDépartement de Sciences Biologiques, Université de Montréal, C.P. 6128, Succ. Centre-Ville, Montréal, QC, Canada H3C 3J7;
^eEnvironmental Chemistry and Technology Program, University of Wisconsin, 660 North Park Street, Madison, WI 53706;
^fFreshwater Institute, Fisheries and Oceans Canada, 501 University Crescent, Winnipeg, MB, Canada R3T 2N6;
^gPenobscot River Mercury Study, 115 Oystercatcher Place, Salt Spring Island, BC, Canada V8K 2W5;
^hDepartment of Geography, University of Toronto, South Building, 3359 Mississauga Road, North Mississauga, ON, Canada L5L 1C6;
ⁱSmithsonian Environmental Research Center, P.O. Box 28, 647 Contees Wharf Road, Edgewater, MD 21037;
^jDepartment of Biological Sciences, University of Alberta, Edmonton, AB, Canada T6G 2E9;
^kChesapeake Biological Laboratory, University of Maryland Center for Environmental Science, University of Maryland, P.O. Box 38, Solomons, MD 20688-0038;
^lDepartment of Chemistry, Trent University, 1600 West Bank Drive, Peterborough, ON, Canada K9J 7B8;
^mU.S. Geological Survey, 8505 Research Way, Middleton, WI 53562;
ⁿOak Ridge National Laboratory, Bethel Valley Road, Oak Ridge, TN 37831-6036;
^oDepartment of Marine Sciences, University of Connecticut, 1080 Shennecossett Road, Groton, CT 06340; and
^pCanadian Forest Service, 1219 Queen Street East, Sault St. Marie, ON, Canada P6A 5M7

Edited by Deborah Swackhamer, University of Minnesota, St. Paul, MN, and accepted by the Editorial Board August 10, 2007 (received for review May 4, 2007)

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Fig. 1.
Three-year average isotopic mercury addition rates (2001–2003) to the upland, wetland, and lake surfaces of the Lake 658 ecosystem at the ELA, northwestern Ontario. The target rate was 22 μg·m⁻²·year⁻¹. The average actual addition rate for the whole catchment was 20.1 μg·m⁻²·year⁻¹, which was 6 times the average wet deposition to this site (3.2 μg·m⁻²·year⁻¹) over the same period.
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Fig. 2.
Mean monthly export of ambient and spike total mercury per square meter of upland and wetland areas.
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Fig. 3.
Annual loadings of spike and ambient mercury to Lake 658 per square meter of lake surface.
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Fig. 4.
Concentrations of lake spike and ambient methylmercury (MeHg) in water (a), sediment trap material (b), the top 2 cm of sediments (c), zooplankton (d), H. azteca (e), and young-of-the-year (YOY) yellow perch muscle samples (f) during 3 years of mercury spike additions to Lake 658 and its watershed. The perch data were measured as total mercury with the assumption that almost all mercury in fish muscle is methylmercury (19). Vertical bars are standard errors.
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Fig. 5.
Percentage increase of methylmercury concentrations in water, sediment trap material, top 2 cm of sediments, and biota resulting from additions of lake spike mercury to Lake 658 over a 3-year period. Vertical bars are standard deviations on the seasonal means. All trends were significantly linear with time (P < 0.05), except for the sediment traps and zooplankton.