Water Resources Research Act Program

Details for Project ID 2014NC188B

Linkages of Mercury and Methane Cycles in Piedmont Streams and Rivers in North Carolina, and Implications for Mercury Bioaccumulation in Food Webs

Institute: North Carolina
Year Established: 2014 Start Date: 2014-05-01 End Date: 2015-04-30
Total Federal Funds: $15,525 Total Non-Federal Funds: $44,475

Principal Investigators: Martin Tsz-Ki Tsui, Craig Allan, Anne Hershey, Stephen Whalen

Project Summary: Methylmercury is a highly toxic compound that extensively bioaccumulates and biomagnifies in aquatic food webs. Methylmercury is produced mainly by anaerobic microbes in the environment, but its processes are not well understood. Methanogens have been recently suggested to be the principal methylators of mercury in freshwater. The proposed research will examine the inter-relationships in the production of methane and methylmercury in Piedmont streams in North Carolina. This research will be the first study examining the biogeochemical coupling of both processes in stream ecosystems, which represent important water resources in North Carolina and elsewhere. The proposed research will conduct a broad survey by measuring total-mercury and methylmercury in streamwater, bulk sediment and sediment porewater, methane in streamwater and porewater, and invertebrate body burdens of methylmercury over time and across different Piedmont streams with gradients of size and land cover patterns. Natural abundance stable mercury isotopes will also be measured in biota to estimate systemspecific photodegradation of methylmercury. In one representative Piedmont stream, detailed experimental work will be carried out to determine the rates of mercury methylation and demethylation in sediment cores, and elucidate the relative importance of different microbial groups controlling these processes. The project is expected to provide new information on how methane cycling is coupled to mercury cycling in Piedmont stream ecosystems where mercury is an on-going socioeconomic problem due to the high levels of methylmercury in fish tissues.