Water Column Methylation in Estuaries

Amina Traore Schartup, Harvard School of Engineering and Applied Sciences, Cambridge, United States, Ryan Calder, Harvard University, Cambridge, MA, United States, Anne Laerke Soerensen, Stockholm University, Department of Applied Environmental Science, Stockholm, Sweden, Robert P Mason, University of Connecticut, Marine Sciences, Groton, United States, Prentiss Balcom, University of Connecticut, Groton, CT, United States and Elsie M Sunderland, Harvard University, T. H. Chan School of Public Health, Boston, United States
Abstract:
Methylmercury (MeHg) is a neurotoxin that bioaccumulates in aquatic food webs and affects humans and wildlife through fish consumption. Many studies have measured active methylation/demethylation in ocean margin sediments but few have reported similar rates for the marine water column. This presentation will review available evidence for water column methylation in estuaries, including new experimental measurements of methylation/demethylation rates from a deep subarctic fjord in Labrador Canada collected in Spring and Fall of 2012-2013. We used these and other data to construct a mass budget for MeHg in the estuary and show that water column methylation (with rates ranging from 1.5 to 2.8 % day-1), is the largest contributor, followed by inputs from rivers (4.9 mol year-1), to the in situ pool of MeHg available for uptake by biota. By contrast, the sediment in this system is a net sink for MeHg (-1.5 mol year-1). We discuss the relationship between observed MeHg and other ancillary environmental factors (organic carbon, sulfur and nutrients) as well as implications for the response time of fish to future changes in mercury inputs.
Back to: The Biogeochemical Cycling of Mercury in the Coastal and Open Ocean I