Freshwater discharges drive high levels of methylmercury in Arctic marine biota

Estuaries are the predominant hunting and fishing territory for northern indigenous populations whose way of life is threatened by both climate change and industrial development. Direct measurements and modeling conducted as part of this study show enhanced production of methylmercury, a potent neurotoxin, and uptake by plankton in stratified oxic seawater. Enhanced climate-driven stratification of ocean margin areas with sea-ice melt will likely elevate biological methylmercury concentrations in the Arctic. Elevated biological methylmercury levels will be exacerbated by hydroelectric development planned throughout many northern regions. Our experimental measurements indicate that, over the next decade, regional increases in methylmercury concentrations resulting from flooding associated with hydroelectric development will be greater than those expected from climate change.