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Mercury contamination of aquatic ecosystems is an issue of national concern, affecting both wildlife and human health. Detailed information on mercury cycling and food-web bioaccumulation in stream settings and the factors that control these processes is currently limited. In response, the U.S. Geological Survey (USGS) National Water-Quality Assessment Program (NAWQA) conducted detailed studies from 2002 to 2006 on various media to enhance process-level understanding of mercury contamination, biogeochemical cycling, and trophic transfer. Eight streams were sampled for this study: two streams in Oregon, and three streams each in Wisconsin and Florida. Streambed-sediment and pore-water samples were collected between...
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Methylmercury production and pore water partitioning of total mercury and methylmercury in streambed sediment is a function of stream drainage basin characteristics. Methylmercury production and pore water partitioning of total mercury and methylmercury in streambed sediment is a function of stream drainage basin characteristics.
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Field and laboratory studies were conducted in April and November 2003 to provide the first direct measurements of the benthic flux of dissolved mercury species (total and methylated forms) between the bottom sediment and water column at two sampling locations within the southern component of San Francisco Bay, California (hereafter referred to as South Bay): one within the main channel and the other in the western shoal area. Because of interest in the effects of historic mercury mining within watersheds that drain into South Bay, the solutes of primary interest were dissolved-mercury species and the predominant ligands that often control mercury speciation (dissolved sulfide and dissolved organic carbon). Benthic...
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Microbial mats are a visible and abundant life form inhabiting the extreme environments in Yellowstone National Park (YNP), WY, USA. Little is known of their role in food webs that exist in the Park's geothermal habitats. Eukaryotic green algae associated with a phototrophic green/purple Zygogonium microbial mat community that inhabits low-temperature regions of acidic (pH ∼ 3.0) thermal springs were found to serve as a food source for stratiomyid (Diptera: Stratiomyidae) larvae. Mercury in spring source water was taken up and concentrated by the mat biomass. Monomethylmercury compounds (MeHg+), while undetectable or near the detection limit (0.025 ng l−1) in the source water of the springs, was present at concentrations...
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The small watershed approach is well-suited but underutilized in mercury research. We applied the small watershed approach to investigate total mercury (THg) and methylmercury (MeHg) dynamics in streamwater at the five diverse forested headwater catchments of the US Geological Survey Water, Energy, and Biogeochemical Budgets (WEBB) program. At all sites, baseflow THg was generally less than 1 ng L−1 and MeHg was less than 0.2 ng L−1. THg and MeHg concentrations increased with streamflow, so export was primarily episodic. At three sites, THg and MeHg concentration and export were dominated by the particulate fraction in association with POC at high flows, with maximum THg (MeHg) concentrations of 94 (2.56) ng L−1...
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