Aquatic Invasive Species Are Short-Circuiting Benefits From Mercury Reduction in the Great Lakes


Research highlights that mercurcy concentrations in fish cannot be predicted by emissions inventories alone.

According to a new study published today [Nov. 4, 2019] 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 upended the food web and forced fish to seek atypical food sources enriched in mercury.

Mercury, or methylmercury as it exists in fish, is a neurotoxin that can cause damage to the nervous system if consumed by people or animals. The study has consequences for health officials and natural resource managers who need the best science possible to inform their decisions, says lead author Ryan Lepak, a postdoctoral researcher at the UW–Madison Aquatic Sciences Center (ASC).

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