Researchers surveying mercury contamination in fish and birds in the northeastern United States and southeastern Canada has identified five "hotspots" where concentrations of the element exceed those established for human or wildlife health.
The US and Canadian research team focused on levels of the potent neurotoxin in yellow perch and common loons, but it also took into account contamination in other fish, birds, and mammals. In addition to these hotspots in New England, New York, and Nova Scotia, the researchers found nine "areas of concern" in these regions and in Quebec and New Brunswick. Findings from the team's analysis are summarized in the January 2007 issue of BioScience.
The hotspots are believed to result from complex processes that move atmospherically released mercury through the environment, and from site-specific characteristics such as the high sensitivity of wetlands and forested areas to mercury inputs. Local sources of mercury are also significant. Although mercury is not directly harmful at ambient levels, it is concentrated up to a millionfold and chemically modified in aquatic food chains, resulting in dangerous levels of methylmercury in some wildlife species.
Greater deposition of mercury near areas that are highly sensitive to the element or that are already affected by it could raise the risk to people and wildlife that consume fish.
There is reason to believe, however, that lowering emissions can reduce risk: an analysis of levels of mercury contamination over time in the Merrimack River watershed suggests that lowered emissions reduced mercury levels in biota within a few years.
David C. Evers of the BioDiversity Research Institute in Gorham, Maine led the 10-member research team. The study was based on samples collected over four years by the Northeastern Ecosystem Research Cooperative and made use of 7311 observations for seven species.
The study report in BioScience is accompanied by an overview article, written by Charles T. Driscoll of Syracuse University and colleagues, that summarizes current knowledge about mercury contamination in the region; the authors conclude that reductions in mercury emissions beyond those currently under way will be needed to eliminate the element as a health risk to humans or to populations of loons.