HR: 16:40h
AN: B14B-03    [Abstracts]
TI: Mercury Cycling in Agricultural and Non-agricultural Wetlands of the Yolo Bypass Wildlife Area, California: Sediment Biogeochemistry
AU: * Marvin-DiPasquale, M C
EM: mmarvin@usgs.gov
AF: U.S. Geological Survey, 345 Middlefield Rd., Mailstop 480, Menlo Park, CA 94025, United States
AU: Windham-Myers, L
EM: lwindham@usgs.gov
AF: U.S. Geological Survey, 345 Middlefield Rd., Mailstop 480, Menlo Park, CA 94025, United States
AU: Alpers, C N
EM: cnalpers@usgs.gov
AF: U.S. Geological Survey, 6000 J St., Placer Hall, Sacramento, CA 95819, United States
AU: Agee, J L
EM: jlagee@usgs.gov
AF: U.S. Geological Survey, 345 Middlefield Rd., Mailstop 480, Menlo Park, CA 94025, United States
AU: Cox, M H
EM: mhcox@usgs.gov
AF: U.S. Geological Survey, 345 Middlefield Rd., Mailstop 480, Menlo Park, CA 94025, United States
AU: Kakouros, E
EM: kaouros@usgs.gov
AF: U.S. Geological Survey, 345 Middlefield Rd., Mailstop 480, Menlo Park, CA 94025, United States
AU: Wren, S L
AF: U.S. Geological Survey, 345 Middlefield Rd., Mailstop 480, Menlo Park, CA 94025, United States
AB: The Yolo Bypass Wildlife Area (YBWA) is part of the larger Yolo Bypass floodwater protection zone associated with the Sacramento River and the Sacramento–San Joaquin Delta, California. Land use in the YBWA consists of white and wild rice fields, seasonally flooded fallow agricultural fields, and permanently and seasonally flooded non-agricultural wetlands used for resident and migratory waterfowl. A recent assessment of mercury (Hg) and methylmercury (MeHg) loads indicates that the Yolo Bypass is responsible for a high proportion of the aqueous MeHg entering the Delta, and that biota from the Yolo Bypass are considerably elevated in MeHg. The current study examines benthic MeHg production and biogeochemical controls on this process, as a function of YBWA land use, wetland management, and agricultural practices during the 2007 rice growing season (June to October). Preliminary results indicate that in the week following initial flooding of agricultural fields, prior to the establishment of rice plants, the microbial community in the 0–2 cm surface sediment zone exhibited very little potential Hg(II)-methylation activity compared to the permanent wetland habitat (as assessed via the 203Hg(II)- methylation assay). Approximately 1 month after flooding, rice plants were established and the activity of the resident Hg(II)-methylating microbial community had increased substantially in all agricultural fields, although the observed rates of MeHg production were still much lower than those observed in the permanent wetland setting. Ongoing field sampling includes analysis of reactive Hg(II) in sediments and of iron and sulfur redox species in sediments and pore waters.
DE: 0402 Agricultural systems
DE: 0408 Benthic processes (4804)
DE: 0432 Contaminant and organic biogeochemistry (0792)
DE: 0461 Metals
DE: 0497 Wetlands (1890)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting