SS3.12 Large Scale Ecosystem Manipulations
Date: Thursday, June 13, 2002
Location: Poster Session - VCC
Connell-HeyesDB, University of Maryland Chesapeake Biological Lab, Solomons, MD, USA,
Heyes, A, , University of Maryland Chesapeake Biological Lab, Solomons, MD, USA,
Gilmour, C, C, Academy of Natural Sciences Estuarine Research Lab, St. Leonard, MD, USA,
Krabbenhoft, D, P, U.S. Geological Survey, Madison, WI, USA,
Mason, R, P, University of Maryland Chesapeake Biological Lab, Solomons, MD, USA,
Controls on Methylmercury Production in Boreal Wetlands.
Wetlands can be significant sources of MeHg to lakes. In this study, we are assessing the sources of Hg for methylation in wetlands, and the importance of key factors controlling net methylation. We hypothesize that Hg methylation and demethylation rates are dynamic, responding to factors that affect the activity of methylators and demethylators, such as temperature, nutrient and sulfur supply, as well as Hg load. As part of the METAALICUS study, we evaluated the importance of these factors using short-term methylation and demethylation potential (rates) in wetlands at the Experimental Lakes Area, northwestern Ontario. Within a location, Hg methylation potential was well correlated with background MeHg concentration. While on short time scales, sulfate addition (to stimulate sulfate reducing bacteria (SRB)) increased methylation of added Hg isotope. Addition of iron oxalate (to stimulate Fe reducers) had no affect. Hg methylation rates varied little over a range of spiked Hg concentrations. Early evidence indicates the activity of methylating bacteria, SRB’s, in these sulfate limited wetlands is more limiting than the bioavailability of in situ Hg, at least in the short term.