Mercury Speciation, Retention and Genomics in Fertilized Salt Marsh Sediments

Friday, 19 December 2014
Caroline Whitley Collins1, Carl H Lamborg2, Kristen Whalen2, Tracy Mincer2, William Buchanan3, Julie A Huber4, Gretchen Swarr2, Priya M Ganguli5 and Anne Bernhard1, (1)Connecticut College, New London, CT, United States, (2)Woods Hole Oceanographic Institution, Woods Hole, MA, United States, (3)Savannah State University, Savannah, GA, United States, (4)Josephine Bay Paul Center, Woods Hole, MA, United States, (5)WHOI, Woods Hole, MA, United States
Recent studies have demonstrated that increased nutrient loading and eutrophication can impact the production of monomethylmercury (MMHg) in marine systems. Experimental plots in Great Sippewisset Marsh (GSM), Falmouth, Massachusetts USA, have been chronically treated with a mixed fertilizer during the growing season since 1971, providing nutrients and other elements, including mercury (Hg) to the salt marsh. To assess the retention, release and methylation of Hg in these marsh sediments in response to fertilization, we collected cores from control, low, high, and extra high fertilization plots across low and high marsh settings. We determined total mercury (HgT) and MMHg concentration and accumulation rates and compared them to those of atmospheric deposition and the loading from the mixed fertilizer. Environmental DNA was extracted from the core sub-samples and polymerase chain reaction (PCR) was used to detect three genes of interest: merA (Hg(II) reducing), hgcA (Hg(II) methylating) and dsrAB (dissimilatory sulfite reduction). Quantitative PCR (qPCR) will be performed in order to overlay the abundance and diversity of the three genes to the Hg profiles and speciation metadata. By comparing the genomic data to the geochemical patterns within the treatment plots we can develop a greater sense of how Hg cycling has changed as a result of fertilization and the overall response of GSM to long-term nutrient loading.