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Environmental Health - Toxic Substances


Mercury in Aquatic Ecosystems

A scientist is applying a solution of water and a isotope of mercury on the shores of a lake.
Applying a solution of water and a stable isotope of mercury (202Hg) on the shores of a lake in the Experimental Lake Area (ELA) in Ontario, Canada. An international team of scientists tracked the applied mercury isotope to study the movement of mercury from the watershed into the lake and fish.

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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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