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An additional result of tampering with the hydrology of the Everglades may be the high levels of mercury in some of the animals of the region. Mercury, familiar as a silvery metallic liquid, forms chemical compounds of various toxicities. Of particular concern in aquatic environments is methlymercury, the highly toxic organically bound form, which readily enters living organisms. It may cause mutations and abnormal growths, as well as neurolgic disorders that may lead to death at higher concentrations. Apparently, methylmercury is being concentrated in the Everglades food web, with predators containing the highest levels. Even in remote areas of the Everglades, fish contain so much mercury that authorities have had to warn fishermen of the dangers of eating them. Animals that feed on aquatic life, such as raccoons and alligators, have also accumulated mercury.
The origin of mercury in the region is not known at this time. Initially, agriculture was suspected because of the use of mercury compounds in some agricultural applications. However, the distribution of mercury levels in the soil, water and biological samples has not supported this notion. One theory is that it occurs naturally in the peat soils of the Everglades. During the last 5,000 years, while the Everglades soils were forming, small amounts of mercury may have become chemically trapped there. Then, during the recent drainage and subsequent oxidation of the peat soils, the mercury would become concentrated and move into the food web. However, another probable contributor is airborne deposition from such sources as incineration of medical and other wastes, paint applications, and fossil-fueled power plants.
The nature and extent of the mercury dilemma is under investigation. It is not yet known, for example, whether mercury is contributing to the demise of the wading bird populations in the Everglades. Mercury appears to be of critical importance, and much more research is needed in order to understand its implications, as well as to determine any possible remediation.
