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U.S. Department of the Interior
U.S. Geological Survey
FS-166-96

Mercury Studies in the Florida Everglades

Background | Mercury in the Geochemical Cycle and Food Chain of the Everglades | The USGS South Florida Ecosystem Program | Mercury Cycling in the Florida Everglades Project | Anticipated Schedule |

Background

Public concern for wildlife and human health problems due to mercury (Hg) toxicity has increased substantially since the mid-1980´s. These concerns are manifested primarily by the issuance of fish consumption advisories in the majority of U.S. states, Canada, and several European countries because of high levels of mercury in game fish. Although the precise causes for this contamination problem are not completely understood, it appears that there are both source and ecosystem-specific factors that can result in elevated levels of mercury in game fish. Because mercury is known to adversely affect the human brain and nervous system, health concerns arise when elevated concentrations of mercury are detected in game fish from ecosystems where there is subsistence level consumption of fish. In extreme cases such as the Everglades, where mercury concentrations in fish consistently exceed the Florida advisory level of 1.5 parts per million, even occasional fish consumption is not recommended.

For most aquatic ecosystems, atmospheric deposition is the primary source of mercury, although there are numerous instances of geologic and anthropogenic point-source contamination. There are many sources of mercury to the atmosphere, both natural and human related. Natural sources include outgassing from the oceans, volcanoes, and natural mercury deposits. Coal combustion, waste incineration, chloralkai production, and metal processing are the dominant human-related sources to the atmosphere. In ecosystems for which atmospheric deposition is the dominant source, resulting concentrations of total mercury in water are very low, generally less than 10 nanograms per liter (ng/L). The challenge to scientists is to explain the series of processes that lead to toxic or near-toxic levels of mercury in organisms near the top of the food chain (bioaccumulation), when aqueous concentrations and source-delivery rates are so low. To understand this phenomenon adequately, scientists must apply an interdisciplinary approach wherein various components of an ecosystem (atmosphere, biota, surface water, ground water, and sediments) are studied contemporaneously. The purpose of this fact sheet is to describe the mercury contamination problem in south Florida, and the interdisciplinary project that was assembled under the auspices of the U.S. Geological Survey South Florida Ecosystem Program to investigate the underlying processes that cause mercury bioaccumulation.

Other Cooperating agencies:

South Florida Water Management District logo Wisconsin Department of Natural Resources logo University of Wisconsin Madison logo
Benedict Estuarine Research Center logo Florida Department of Environmental Protection logo



Next: Mercury in the Geochemical Cycle and Food Chain of the Everglades


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For more information contact:

David Krabbenhoft
U.S. Geological Survey
6417 Normandy Lane
Madison, WI 53719
(608) 276-3843
dpkrabbe@usgs.gov

Related information:

SOFIA Project: Aquatic Cycling of Mercury in the Everglades (ACME)



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Last updated: 04 September, 2013 @ 02:03 PM(TJE)