HR: 17:45h
AN: B14B-07    [Abstracts]
TI: The Influence of Hurricanes and Other Biogeochemical Factors on Net Mercury Methylation and Mercury Cycling in the Gulf of Mexico
AU: * Mason, R
EM: robert.mason@uconn.edu
AF: University of Connecticut, Department of Marine Sciences, Groton, CT 06340, United States
AU: Bank, M
EM: mbank@hsph.harvard.edu
AF: Harvard University, Harvard School of Public Health, Boston, MA 02115, United States
AU: Hollweg, T
EM: terill.hollweg@uconn.edu
AF: University of Connecticut, Department of Marine Sciences, Groton, CT 06340, United States
AU: Liu, B
EM: bliu@hsph.harvard.edu
AF: Harvard University, Harvard School of Public Health, Boston, MA 02115, United States
AU: Rabalais, N
EM: nrabalais@lumcon.edu
AF: Louisiana Universities Marine Consortium Louisiana Universities Marine Consortium, 8124 Highway 56, Chauvin, Louisiana 70344, 8124 Highway 56, Chauvin, LA 70334, United States
AU: Schaider, L
EM: lschaide@hsph.harvard.edu
AF: Harvard University, Harvard School of Public Health, Boston, MA 02115, United States
AU: Senn, D
EM: dsenn@hsph.harvard.edu
AF: Harvard University, Harvard School of Public Health, Boston, MA 02115, United States
AU: Shine, J
EM: jshine@hsph.harvard.edu
AF: Harvard University, Harvard School of Public Health, Boston, MA 02115, United States
AU: Swarzenski, P
EM: pswarzen@usgs.gov
AF: USGS, Center for Coastal and Watershed Studies, St. Petersburg, FL 33701, United States
AB: Methylation of mercury (Hg) in coastal region sediments is a potentially important source of methylmercury (MeHg) to ocean food webs. Sediment Hg studies in the coastal zone have focused mostly on biogeochemical relationships but have not studied in detail the impact of extreme events, such as hurricanes, on Hg dynamics. As a result of two funded studies, samples were collected at a number of stations in July and October 2005 and March and July 2006 in the Gulf region, and covering locations impacted by both Hurricanes Katrina and Rita. Some locations are also impacted by seasonal hypoxia. Sediment cores were analyzed for total Hg, MeHg, and ancillary variables, and were also dated using various proxies. Rates of methylation (km) and demethylation (kd) were also estimated using stable isotopes of Hg and MeHg. Typical relationships were found for bulk sediment parameters, and for dissolved-particulate partitioning and these relationships will be discussed. The impact of the hurricane disturbance was clearly evident from large differences before and after in the sediment profiles of Hg, MeHg, sediment organic matter content (TOC) and other bulk elemental concentrations, as measured by XRF. Additionally, measurements of radiotracer distributions (7Be, 210Pb), from this and other studies confirm the substantial redistribution of sediments as a result of the hurricanes. Hurricane disturbances appear to have stimulated net Hg methylation by increasing the methylation rate and depressing the demethylation rate, and as evidenced by the higher %MeHg, at the highly disturbed sites. Our results also suggest there has been a further redistribution of sediments post-hurricanes. In total, we estimate that the amount of Hg moved and redistributed as a result of the hurricanes was substantially greater than the yearly input of Hg from the Mississippi/Atchalfalaya rivers and the atmosphere. This redistribution suggests that historically deposited Hg needs to be considered when evaluating inputs of Hg in terms of the potential availability of Hg within the ecosystem to Hg methylation. Overall, large physical disturbances have the potential to be important drivers of net Hg methylation, likely through providing fresh organic matter to the methylating sulfate reducing organisms, through the overall oxygenation of the sediment column, and by redistributing buried Hg into bioactive sediment layers. The implications of these results will be discussed.
DE: 0409 Bioavailability: chemical speciation and complexation
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0442 Estuarine and nearshore processes (4235)
DE: 0461 Metals
DE: 0489 Trace element cycling (4875)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting