Canadian and U.S. scientists have, for the first time, shown mercury levels in fish respond directly to changes in the chemical's atmospheric deposition.

"Up to now a direct link has been difficult to establish because of all the other factors that affect mercury levels in fish and large pools of mercury already in the environment," said lead author Reed Harris of Tetra Tech. "By adding stable mercury isotopes to an entire ecosystem for several years, our team was able to zero in on the effects of changing atmospheric mercury deposition."

The isotopes allowed the team to distinguish between experimentally applied mercury and mercury already present in the ecosystem and to examine bioaccumulation of mercury deposited to different parts of the watershed. The scientists determined fish methylmercury concentrations responded rapidly to changes in mercury deposition over the first three years of study.

"The results were very dramatic," said co-author Andrew Heyes of the University of Maryland. "Using the stable isotope approach has revealed a great deal about the cycling of mercury in watersheds."

The research, co-written by 24 scientists from Canada and the United States, is featured in this week’s Proceedings of the National Academy of Sciences. // Copyright 2007 by United Press International


Publication date: 19 September 2007   

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