Keeping an eye on mercury

Mercury kills, and its presence in the environment is an indicator of potential trouble on the horizon for all species, including humans. Anthony DePalma reports in the NYT on a study recently released by the BioDiversity Research Institute on increased levels of mercury in Bald Eagles in the Catskill Mountains region of New York.


We've known for quite a few years that mercury was a problem in the northeastern U.S. and southeastern Canada. Charlie Driscoll and his colleagues, working under the umbrella of the Hubbard Brook Research Foundation, reviewed the existing data on mercury deposition in the Northern Appalachian ecoregion and showed that mercury levels here routinely exceed human and wildlife health thresholds. Chris Rimmer, at the Vermont Center for Ecostudies, and his colleagues reported in the journal Ecotoxicology in 2005 that even an upland species like Bicknell's Thrush, which inhabits high elevation forests in the Northern Appalachians during the breeding season, has levels of mercury in its blood in excess of accepted health thresholds.

The presence of mercury in a species like Bicknell's Thrush is particularly disturbing. While still not acceptible, mercury in Bald Eagles is at least understandable. Ionic forms of mercury deposited in aquatic ecosystems are converted into methylmercury (a form that causes severe neurological damage and death) by bacteria; methylmercury is then bioaccumulated up through the aquatic food chain and eventually gets incorporated into the tissues of Bald Eagles, which eat a lot of fish.

But Bicknell's Thrush? Either this upland songbird eats far more aquatic insect larvae than previously understood (and methylmercury is bioaccumulating in these short-lived insects to a much greater extent than previously believed) or there are terrestrial pathways from ionic mercury to methylmercury that we don't fully understand, which means that more species are susceptible to mercury poisoning than we thought.

Either way, it's not good news. And neither is the fact that mercury levels are on the rise.

Read More......