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Investigation of Total and Methyl Mercury in Fish and Sediment of Lake Michigan
Citation:
ROSSMANN, R. Investigation of Total and Methyl Mercury in Fish and Sediment of Lake Michigan. Presented at 2008 Integrating Multimedia Measurements of Mercury in the Great Lakes Region Workshop, La Crosse, WI, November 10 - 12, 2008.
Impact/Purpose:
Sediment analyses of the dated sediment cores are being used to describe the spatial and temporal variation of total mercury fluxes to the lake, mercury concentrations in the sediments, the history of mercury loads to the lake, and how to interpret cores collected from large water bodies where resuspension/deposition processes lead to sediment focusing and time delays for delivery of mercury loaded nearshore to offshore regions of the lake. Methyl mercury analyses of the cores continues to this date. Enough cores have been analyzed to document in situ production of methyl mercury in the sediments.
Description:
Sediment cores and fish collected between 1994 and 1996 as part of the Lake Michigan Mass Balance Project were analyzed for total and methyl mercury. Results of the fish analyses are being used to describe total and methyl mercury concentrations in forage fish and lake trout, review historical trends for lake trout, and to understand bioaccumulation within the food chain. Fish collected from three regions of the lake during five sampling periods between 1994 and 1995 by the USGS Great Lakes Science Center included lake trout, alewife, slimy sculpin, deepwater sculpin, rainbow smelt, and bloater. These were received as whole-fish composites usually containing five fish. For bloater, lake trout, and alewife, two or more size groups based on length were received. USGS Great Lakes Science Center provided a variety of information including sample location, date of collection, length, weight, age, moisture content, diet, and number of fish homogenized. Box cores of sediment were collected by the NOAA Great Lakes Environmental Research Laboratory, University of Wisconsin-Milwaukee Great Lakes Center, and USEPA between 1994 and 1996. Cores were Pb-210 dated by the NOAA Great Lakes Environmental Research Laboratory and the University of Wisconsin-Milwaukee Center for Great Lakes Studies. Sediment analyses of the dated sediment cores are being used to describe the spatial and temporal variation of total mercury fluxes to the lake, mercury concentrations in the sediments, the history of mercury loads to the lake, and how to interpret cores collected from large water bodies where resuspension/deposition processes lead to sediment focusing and time delays for delivery of mercury loaded nearshore to offshore regions of the lake. Methyl mercury analyses of the cores continues to this date. Enough cores have been analyzed to document in situ production of methyl mercury in the sediments.