title: Contrasting effects of marine and terrestrially derived dissolved organic matter on mercury speciation and bioavailability in seawater.
abstract: Methylmercury (MeHg) is the only species of mercury (Hg) to biomagnify in aquatic food-webs to levels that are a widespread concern for human and ecological health. Here we investigate the association between dissolved organic matter (DOM) in seawater and Hg speciation and uptake using experimental data and field measurements from Long Island Sound (LIS) and the Northwestern Atlantic continental margin. We measured differences in DOM composition across sampling stations using excitation emission matrix fluorescence spectroscopy and further separated DOM into terrestrial and marine components using Parallel Factor Analysis (PARAFAC). Highest MeHg concentrations were found in the estuarine stations (LIS) with highest DOM concentrations due to enhanced external inputs from the watershed and rivers. For stations on the shelf and slope, MeHg in plankton increased linearly with a decreasing fraction of fluorescence attributable to DOM components with a terrestrial rather than marine origin. These results are corroborated by experimental data showing higher MeHg uptake by cells in the presence of predominantly marine DOM compared to terrestrial DOM. Highest fractions of dissolved gaseous mercury were also found at stations with the highest marine DOM content, suggesting a greater reducible fraction of divalent inorganic Hg. These data suggest DOM composition is a critical driver of Hg reactivity and bioavailability in offshore marine waters.
authors: †Department of Environmental Health, Harvard School of Public Health, Boston, Massachusetts 02215, United States.
authors: Amina T
authors: AT
authors: Schartup
authors: ‡Department of Environmental Science, Rutgers University, 14 College Farm Road, New Brunswick, New Jersey 08901, United States.
authors: Udonna
authors: U
authors: Ndu
authors: §Department of Marine Sciences, University of Connecticut, 1080 Shennecossett Road, Groton, Connecticut 06340, United States.|∥School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, United States.
authors: Prentiss H
authors: PH
authors: Balcom
authors: §Department of Marine Sciences, University of Connecticut, 1080 Shennecossett Road, Groton, Connecticut 06340, United States.
authors: Robert P
authors: RP
authors: Mason
authors: †Department of Environmental Health, Harvard School of Public Health, Boston, Massachusetts 02215, United States.|∥School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, United States.
authors: Elsie M
authors: EM
authors: Sunderland
mesh_terms: D001419:Bacteria / Q000378:metabolism; D001682:Biological Availability; D005163:Factor Analysis, Statistical; D005843:Geography; D008628:Mercury / Q000032:analysis*; D008767:Methylmercury Compounds / Q000032:analysis; D009930:Organic Chemicals / Q000032:analysis*; D010933:Plankton / Q000378:metabolism; D012623:Seawater / Q000737:chemistry*; D012995:Solubility; D013050:Spectrometry, Fluorescence; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D008767:Methylmercury Compounds; D009930:Organic Chemicals; D014874:Water Pollutants, Chemical; D008628:Mercury