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National Water-Quality Assessment (NAWQA) Program

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Under certain environmental conditions(low dissolved oxygen and the presence of sulfate and organic material), inorganic mercury can be converted to methylmercury, a toxic form of mercury that poses a toxicological risk to aquatic life and humans.  These conditions are often found in wetlands, such as those in the St. Mary's River basin in Florida.
Under certain environmental conditions(low dissolved oxygen and the presence of sulfate and organic material), inorganic mercury can be converted to methylmercury, a toxic form of mercury that poses a toxicological risk to aquatic life and humans. These conditions are often found in wetlands, such as those in the St. Mary's River basin in Florida.
NAWQA Mercury Study Areas
Santee | Hudson | Wisconsin | Recon Survey
NAWQA Mercury Study Areas Santee Study Unit Hudson Study Unit Lake Michigan

Mercury in Stream Ecosystems

Hg Home Background Publications Contacts USGS Mercury Other Links

The NAWQA Program is studying mercury cycling in watersheds across the Nation to build an understanding of how natural features and human activities affect the transformation, transport, and bioaccumulation of mercury in stream ecosystems. As of August 2008, mercury was the second leading cause of stream impairment throughout the Nation USEPA 303(d) list). Methylmercury is a neurotoxin that is biomagnified in aquatic food webs so that piscivorous fish and wildlife, and humans that consume fish, are potentially at greater risk of exposure to methylmercury. USGS data and research may aid in the development of more rigorous models that relate water quality to mercury bioaccumulation, thereby enhancing capabilities for predicting mercury contamination in fish.


Featured Research

Our 2nd group of studies focused on small streams in the upper Hudson River Basin in the Adirondacks of New York State, and in the upper Edisto River Basin in the Coastal Plain of South Carolina. Our publications, including those resulting from collaboration with other scientists, are available for download from our Publications page. Detailed methods, data sets, and descriptions of study areas are available in the Methods and Data section of our Publications page.

Papers incorporating data from intensive studies in Oregon, Wisconsin, Florida, New York, and South Carolina Intra- and inter-basin comparisons | new Bioaccumulation factors

Papers focused on the contrasting upper Hudson River and upper Edisto River basins. Biota: macroinvertebrates and fishes | influence of dietary carbon | Stream water: Spatial and seasonal variability | Intra- and inter-basin comparisons

Papers focused on the upper Hudson River basin: SUVA as an indicator | Landscape controls | Mobilization of mercury and dissolved organic carbon

Papers focused on the upper Edisto River basin:new Climate change and watershed mercury export | Shallow groundwater mercury supply | Hydrology and methylmercury availability | Flood hydrology and methylmercury | Dynamic modeling

How Mercury Flows Downstream features three papers on mercury cycling in stream ecosystems from our first group of studies, in Oregon, Wisconsin, and Florida.

Mercury trends in fish from rivers and lakes in the United States, 1969–2005. Major Findings | Data | Technical Announcement

Mercury in fish, water, and sediment in U.S. streams. Press Release | Podcast | Major findings | Selected press coverage (*): USA Today; WKOW; MSNBC; FSRN; MSNBC; LA Times; Economist; Nature; DL.



Key Research Questions


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Frequently Asked Questions about mercury in aquatic ecosystems

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