Mercury in Aquatic Ecosystems

Mercury occurs naturally in the environment and cycles among the atmosphere, water, and sediments. Human activities such as coal burning power plants and waste incineration increase the amount of mercury cycling in the environment. Since the industrial revolution, anthropogenic mercury emissions have increased atmospheric mercury levels about threefold, causing corresponding increases in mercury levels in terrestrial and aquatic ecosystems.

Mercury that is released into the atmosphere can be transported long distances and deposited in aquatic ecosystems, where it is methylated to methylmercury. Mercury is a neurotoxicant, to which the human fetus is very sensitive. Methylmercury is an organic form of mercury, the most toxic form, and the form that bioaccumulates in fish. Wildlife and humans are exposed primarily through consumption of contaminated fish. The factors that make some aquatic ecosystems susceptible to this bioaccumulation, however, are unknown, making protection of human health and the health of fish-eating wildlife a challenge.

Research focuses on the processes of mercury methylation and accumulation in aquatic ecosystems, factors that determine ecosystem susceptibility, and investigation of whether reduced emissions will reduce mercury accumulation in susceptible ecosystems.

• National and Regional Assessments of Mercury Occurrence and Cycling in the Environment
• Mercury Experiment to Assess Atmospheric Loading in Canada and the United States (METAALICUS)
• Mercury Cycling in Aquatic Ecosystems

Aquatic ecosystems across the Nation are being studied to identify the factors that control where and when mercury accumulates to toxic levels in the food chain

Program Headlines Related to Mercury Research

• Mercury Concentrations in Streams Found to Go Through Daily Cycles
• USGS Mobile Atmospheric Mercury Laboratory Makes an Impact
• National Fish Mercury Model Available On-Line
• OSTP Report on Methylmercury in the Gulf of Mexico
• Glacial Ice Cores Reveal the History of Global Mercury Contamination
• Mercury-Contaminated Fish--Is it Old or New Mercury?

Fact Sheets

• Are Walleye from Lake Roosevelt Contaminated with Mercury?: USGS Fact Sheet FS-102-97
• Glacial Ice Cores Reveal a Record of Natural and Anthropogenic Atmospheric Mercury Deposition for the Last 270 Years: USGS Fact Sheet FS-051-02
• Mercury Contamination of Aquatic Ecosystems: USGS Fact Sheet FS-216-95
• Mercury Contamination from Historic Gold Mining in California: USGS Fact Sheet FS-061-00

More information on Mercury Research

• Mercury Research in the USGS, Provides information on mercury research across a wide spectrum of U.S. Geological Survey science programs
• USEPA Mercury Page
• Fish Consumption Advisories (USEPA)

New Publications

• Wetlands as principal zones of methylmercury production in southern Louisiana and the Gulf of Mexico region: Hall, B.D., Aiken, G.R., Krabbenhoft, D.P., Marvin-DiPasquale, M., and Swarzenski, C.M., 2008, Environmental Pollution, v. 154, no. 1, p. 124-134, doi:10.1016/j.envpol.2007.12.017.
• Comparison of total mercury and methylmercury cycling at five sites using the small watershed approach: Shanley, J.B., Mast, A.M., Campbell, D.H., Aiken, G.R., Krabbenhoft, D.P., Hunt, R.J., Walker, J.F., Schuster, P.F., Chalmers, A., Aulenbach, B.T., Peters, N.E., Marvin-DiPasquale, M., Clow, D.W., and Shafer, M.M., 2008, Environmental Pollution, v. 154, no. 1, p. 143-154, doi:10.1016/j.envpol.2007.12.031.
• Influence of natural dissolved organic carbon on the bioavailability of mercury to a freshwater alga: Gorski, P.R., Armstrong, D.E., Hurley, J.P., and Krabbenhoft, D.P., 2008, Environmental Pollution, v. 154, no. 1, p. 116-123 doi:10.1016/j.envpol.2007.12.004.
• Transport of elemental mercury in the unsaturated zone from a waste disposal site in an arid region: Walvoord, M.A., Andraski, B.J., Krabbenhoft, D.P., and Striegl, R.G., 2008, Applied Geochemistry, v. 23, no. 3, p. 572-583, doi:10.1016/j.apgeochem.2007.12.014.
• A comparison of winter mercury accumulation at forested and no-canopy sites measured with different snow sampling techniques: Nelson, S.J., Johnson, K.B., Weathers, K.C., Loftin, C.S., Fernandez, I.J., Kahl, J.S., and Krabbenhoft, D.P., 2008, Applied Geochemistry, v. 23, no. 3, p. 384-398, doi:10.1016/j.apgeochem.2007.12.009.
• Characterization and cycling of atmospheric mercury along the central US Gulf Coast: Engle, M.A., Tate, M.T., Krabbenhoft, D.P., Kolker, A., Olson, M.L., Edgerton, E.S., DeWild, J.F., and McPherson, A.K., 2008, Applied Geochemistry, v. 23, no. 3, p. 419-437, doi:10.1016/j.apgeochem.2007.12.024.