Collaborative Research: GEOTRACES Arctic Section: Mercury Speciation and Cycling in the Arctic Ocean

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In this project, investigators from Woods Hole Oceanographic Institution and Wright State University participating in the 2015 U.S. GEOTRACES Arctic expedition will measure total mercury and mercury species in seawater, particles, sediments, snow and sea-ice samples to better understand its cycling in the Arctic Ocean. In common with other multinational initiatives in the International GEOTRACES Program, the goals of the U.S. Arctic expedition are to identify processes and quantify fluxes that control the distributions of key trace elements and isotopes in the ocean, and to establish the sensitivity of these distributions to changing environmental conditions. Some trace elements are essential to life, others are known biological toxins, and still others are important because they can be used as tracers of a variety of physical, chemical, and biological processes in the sea. In its methylated form, mercury poses a serious human and ecosystem health threat, and this research will provide important information on the extent and rate of change of mercury in the sensitive Arctic ecosystem. Results from this study will be shared through outreach efforts to middle schools students in the Dayton, Ohio area, and the research will involve training for graduate and undergraduate students.Mercury is a toxic trace metal that originates from natural and anthropogenic sources, and can enter the oceans through many processes, most importantly atmospheric deposition, riverine discharge, and coastal erosion in the Arctic Ocean. Mercury in the ocean can be transformed into varying species by a variety of abiotic and biotic processes. Its transformation to methylmercury is of primary concern as it can biomagnify in food webs. Wildlife in the Arctic has experienced unprecedented increases of methylmercury in their tissues during the past 200 years. While there has been a great deal of research related to mercury cycling in the Arctic in recent years, there remain large gaps in fundamental understanding, particularly with respect to mercury distributions and speciation. The researchers will 1) measure the concentration of four mercury species in the water column, particles, sediments, snow and sea-ice samples, 2) determine the concentration of other related chemical species (thiols and snow/ice bromine), and 3) explore the mercury-related genomics of bacteria in various samples. Results from this work will yield new insights into the extent and rate of change of mercury loadings in the Arctic Ocean.