SS4.02 The Role of Microbiology in Trace Metal and Organic Contaminant Cycling in Aquatic Systems
Date: Wednesday, June 12, 2002
Time: 9:45:00 AM
Location: Esquimalt
 
JohnsonBM, Water Resources Science, University of Minnesota, St. Paul, MN, USA, john4063@tc.umn.edu
Cotner, J, B, Ecology, Evolution, and Behavior, University of Minnesota, St. Paul, MN, USA, cotne002@tc.umn.edu
Brezonik, P, L, Civil Engineering, University of Minnesota, Minneapolis, MN, USA, brezo001@umn.edu
 
ROLE OF SULFATE REDUCING BACTERIA IN METHYL MERCURY FLUX FROM FRESHWATER SEDIMENTS
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We investigated the role of sulfate reducing bacteria in the methylation of mercury in sediments from a seepage lake located in northern Minnesota. We performed two sets of experiments to elucidate the effects of sulfate and carbon availability on Hg methylation rates, one with slurried sediments and another with intact cores. The experiment with intact lake sediment core microcosms was incubated under anoxic conditions using a flow-through system. Organic carbon availability had more influence on methyl-Hg fluxes than sulfate availability. The highest methyl-Hg flux occurred in sulfate plus lactate amended cores. Average methyl-Hg sediment fluxes were 1.74 ug/m2/yr for sulfate plus lactate amended cores, whereas fluxes in control cores were less than 0.33 ug/m2/yr, and fluxes in sulfate-only amended cores were only 0.55 ug/m2/yr. Measurements of dissolved inorganic carbon fluxes indicated that sulfate stimulated respiration in carbon-amended cores. The purpose of the second experiment with slurried lake sediment will be to determine the sulfate concentration for optimal methyl-Hg production along with influence of non-limiting carbon conditions.