Mercury in Aquatic Ecosystems
The location of the maximum methylmercury concentration at depth in the Pacific Ocean was the first evidence noted by the researchers pointing to the new methylation cycle. The graphic shows sampling depth on the left (in meters), and oxygen concentration on the right (in micromoles per kilogram of seawater [µmol/kg]) along a north-south latitudinal transect in the eastern North Pacific Ocean. The specific depth of maximal methylmercury concentration was consistently found at the ocean depth where the most rapid loss of oxygen was also observed. The process linking these two observations is microbial decomposition of "ocean rain", which is settling algae produced near the surface of the ocean. The decomposition process consumes oxygen from the water, but also leads to unintended methylmercury production.
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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
More information on Mercury Research
- Mercury concentrations and distribution in soil, water, mine waste leachates, and air in and around mercury mines in the Big Bend region, Texas, USA: Gray, J.E., Theodorakos, P.M., Fey, D.L., and Krabbenhoft, D.P., 2014, Environmental Geochemistry and Health, doi:10.1007/s10653-014-9628-1 (Advanced Web release).
- Effects of urbanization on mercury deposition and accumulation in New England: Chalmers, A.T., Krabbenhoft, D.P., Van Metre, P.C., and Nilles, M.A., 2014, Environmental Pollution, v. 192, p. 104-112, doi:10.1016/j.envpol.2014.05.003.
- Methylmercury production in sediment from agricultural and non-agricultural wetlands in the Yolo Bypass, California, USA: Marvin-DiPasquale, M., Windham-Myers, L., Agee, J.L., Kakouros, E., Kieu, L.H., Fleck, J., Alpers, C.N., and Stricker, C., 2014, Science of the Total Environment, v. 484, no. 1, p. 288-299, doi:10.1016/j.scitotenv.2013.09.098.
- Mercury cycling in agricultural and managed wetlands, Yolo Bypass, California--Spatial and seasonal variations in water quality: Alpers, C.N., Fleck, J.A., Marvin-DiPasquale, M., Stricker, C.A., Stephenson, M., and Taylor, H.E., 2014, Science of the Total Environment, v. 484, no. 1, p. 276-287, doi:10.1016/j.scitotenv.2013.10.096.
- Mercury in the soil of two contrasting watersheds in the eastern United States: Burns, D.A., Woodruff, L.G., Bradley, P.M., and Cannon, W.F., 2014, PLoS ONE, v. 9, no. 2, p. e86855, doi:10.1371/journal.pone.0086855.
- Mercury cycling in agricultural and managed wetlands of California, USA--Experimental evidence of vegetation-driven changes in sediment biogeochemistry and methylmercury production: Windham-Myers, L., Marvin-DiPasquale, M., Stricker, C.A., Agee, J.L., Kieu, L.H., and Kakouros, E., 2014, Science of the Total Environment, v. 484, p. 300-307, doi:10.1016/j.scitotenv.2013.05.028.
- Mercury cycling in agricultural and managed wetlands--A synthesis of methylmercury production, hydrologic export, and bioaccumulation from an integrated field study: Windham-Myers, L., Fleck, J.A., Ackerman, J.T., Marvin-DiPasquale, M., Stricker, C.A., Heim, W.A., Bachand, P.A.M., Eagles-Smith, C.A., Gill, G., Stephenson, M., and Alpers, C.N., 2014, Science of the Total Environment, v. 484, no. 1, p. 221-231, doi:10.1016/j.scitotenv.2014.01.033.
- Lacustrine responses to decreasing wet mercury deposition rates--Results from a case study in northern Minnesota: Brigham, M.E., Sandheinrich, M.B., Gay, D.A., Maki, R.P., Krabbenhoft, D.P., and Wiener, J.G., 2014, Environmental Science and Technology, doi:10.1021/es500301a (Advanced Web release).
- Mercury and methylmercury stream concentrations in a coastal plain watershed--A multi-scale simulation analysis: Knightes, C.D., Golden, H.E., Journey, C.A., Davis, G.M., Conrads, P.A., Marvin-DiPasquale, M., Brigham, M.E., and Bradley, P.M., 2014, Environmental Pollution, v. 187, p. 182-192, doi:10.1016/j.envpol.2013.12.026.
- Spatial distribution of mercury in southeastern Alaskan streams influenced by glaciers, wetlands, and salmon: Nagorski, S.A., Engstrom, D.R., Hudson, J.P., Krabbenhoft, D.P., Hood, E., Dewild, J.F., and Aiken, G.R., 2014, Environmental Pollution, v. 184, p. 62-72, doi:10.1016/j.envpol.2013.07.040.