Methylmercury Production in the Coastal Zone: An Important Source of Methylmercury to Marine Fish?
Rob Mason, Dept. of Marine Sciences, University of Connecticut
23 Mar 2007
The methylation of inorganic mercury (Hg) to the more toxic methylmercury (MeHg) in sediment is the most important process linking the input of inorganic Hg from the atmosphere and other sources to MeHg bioaccumulation in the aquatic food chain. However, there is a lack of data on Hg methylation in estuarine systems and on the oceanic shelf and slope, and little examination of the potential for these sources to be important to bioaccumulation into ocean food chains. The talk will focus on our studies aimed at understanding the biochemical factors affecting Hg methylation in the coastal ocean, and the potential for the continental shelf serving as a source of MeHg to open-water fish. Data from sediment cores collected from nine stations in the Chesapeake Bay and on the mid-Atlantic continental shelf will be discussed along with measurements of Hg methylation and demethylation rates, and sulfate reduction rates. The data provides evidence of MeHg production on the mid-Atlantic continental shelf and slope, and suggests that these sites are potential sources of methylmercury to the aquatic food web and open-water fish. The implications of the results will be discussed in terms of our studies and those of others.