U.S. GEOTRACES: Distribution of Mercury Species in the Western Arctic Ocean

Many predatory marine mammals and seabirds in the Arctic have mercury (Hg) concentrations high enough to cause adverse effects in wildlife; however, the distribution of Hg species in the Arctic Ocean is unknown and there is uncertainty regarding the sources of Hg to the ocean basin and its internal production of bioaccumulative monomethylmercury. We made Hg speciation measurements on board the USCGC Healy during the U.S. GEOTRACES section of the western Arctic Ocean in Fall 2015 with the goal of constructing a high-resolution vertical and horizontal section of total mercury, monomethylmercury, dimethylmercury, and elemental Hg in seawater of this important ocean region.  Sampling began with a Pacific end-member station off the shelf-break of the Bering Sea and continued through the Bering Strait and over the shallow Chukchi shelf before heading into deep waters of the Canada and Makarov basins and ultimately the North Pole.  High-quality speciation results from the international GEOTRACES program are important to understanding the cycling of Hg in the Arctic Ocean, its bioaccumulation in polar marine wildlife, and potential impacts of climate change on these processes.