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Environmental Health - Toxic Substances


Mercury in Aquatic Ecosystems

Mound Spring, Sentinel Meadows, Yellowstone National Park, Wyo.
USGS scientists have detected naturally occurring methylmercury in many of the Yellowstone National Park's hot springs, such as Mound Spring, Sentinel Meadows, Wyoming.

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Mercury Research in the USGS

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
Mercury contamination figure
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

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