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.

Circular 1395
Mercury in the Nation's Streams -- Levels, Trends, and Implications

Technical Announcement
Presentation (coming soon)

Featured Graphics    next -->

Burning coal for energy production was the single largest component of anthropogenic mercury emissions in the United States during 2005, accounting for slightly more than one-half of the total.

Methylmercury concentrations in fish and stream water generally were highest in undeveloped areas with abundant wetlands, which provide ideal conditions for methylmercury production. In contrast, methylmercury  levels in largemouth bass from urban streams were the lowest of all land uses.

Methylmercury concentrations in aquatic organisms increase with increasing methylmercury concentrations in water and with increasing trophic level. Fish at the top of the food web tend to have the highest concentrations of methylmercury.

NAWQA Mercury Study Areas
Santee | Hudson | Wisconsin | Recon Survey

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 | 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: 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

• What controls concentrations of mercury in stream water, sediment, and fish?
• How do biological, chemical, and other environmental characteristics govern the methylation, transport, and bioaccumulation of mercury in streams?

Links

• Toxic Substances Hydrology Program
• Mercury in the Environment

Frequently Asked Questions about mercury in aquatic ecosystems