Invasive species short-circuiting benefits from mercury reduction in the Great Lakes

Using a combination of mercury, nitrogen and carbon isotope analysis — which he terms “fingerprinting” — on samples of lake trout archived from 1978 to 2012, researcher Ryan Lepak discovered there wasn’t an obvious decrease in concentrations of mercury in these fish even though the sediment record revealed reduced mercury loading. The new study shows this is due to shifts in the fish’s diet. Credit: Ryan Lepak

According to a new study published today in the Proceedings of the National Academy of Sciences, 40 years of reduced mercury use, emissions, and loading in the Great Lakes region have largely not produced equivalent declines in the amount of mercury accumulating in large game fish.

Researchers, including those from the University of Wisconsin-Madison, say it’s largely due to aquatic invasive species in Lake Michigan—primarily quagga and zebra mussels—that have…

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