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:Benedict Estuarine Research Center logo




Next: Mercury in the Geochemical Cycle and Food Chain of the EvergladesFor more information contact:David Krabbenhoft
            U.S. Geological Survey
            6417 Normandy Lane
            Madison, WI 53719
            (608) 276-3843dpkrabbe@usgs.gov

Related information:SOFIA Project: Aquatic Cycling of Mercury in the Everglades (ACME)
U.S. Department of the Interior, U.S. Geological Survey, Center for Coastal Geology
This page is: http://sofia.usgs.gov/publications/fs/166-96/print.htmlComments and suggestions? Contact: Heather Henkel - Webmaster
Last updated: 11 October, 2002 @ 09:31 PM

(KP)