New study shows fish respond quickly to changes in mercury ...( Reducing atmospheric mercury emissio...)

Reducing atmospheric mercury emissions should quickly reduce mercury levels in lake fish, according to a three-year study published this week in the Proceedings of the National Academy of Science. The study showed that an increase in mercury loading at rates relevant to atmospheric deposition resulted in a significant increase in methylmercury production and accumulation in fish in only three years.

This is good news. It means that a reduction in new mercury loads to many lakes should result in lower mercury in fish within a few years, said Cynthia Gilmour, scientist at the Smithsonian Environmental Research Center and a co-investigator in the study.

While recent federal and state regulations aimed at reducing mercury levels in fish require reductions in mercury emissions, the potential effectiveness of these controls and the time frame of the response were previously unknown.

Some have speculated that it could take decades to see the impact of emissions reductions on mercury levels in fish. Centuries of human-derived mercury releases to the atmosphere have resulted in elevated amounts of mercury in sediments and soils across most of the globe. If this historical mercury contamination contributes substantially to mercury in fish, reductions in current emissions may have little impact in the foreseeable future.

The study, Mercury Experiment to Assess Atmospheric Loading in Canada and the United States, found that methylmercury (the type that accumulates in fish) was more readily produced from newly deposited mercury than from historical mercury contamination already buried in lake sediments. This means that methylmercury in lakes should decline quickly if mercury deposition is reduced.

Additionally, the study team found that mercury added directly to the lake surface was rapidly accumulated into fish, while essentially none of the mercury deposited to the lakes watershed was found in fish after three years. This
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