Collaborative Proposal: "SG" Identifying Sources and Degradation Mechanisms of Methylmercury in Temperate Forest Ecosystems

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This project is aimed at understanding the cycling of mercury, including the mechanisms of its transformation into the highly-toxic form, methylmercury, in terrestrial systems. Mercury is naturally present in ecosystems, but also comes from human sources. Methylmercury bio-accumulates in food webs and can threaten forest organisms such as songbirds. This research will examine mercury cycling in four different temperate forests across the United States using mercury stable isotope analysis of forest food webs. This technique can fingerprint the methylmercury in forest organisms and help determine the pathways and sources including rain, soil and tree leaves. After obtaining the isotope fingerprint of all samples, statistical models will be used to estimate the relative contribution of each source (precipitation, soil and tree leaves) to methylmercury accumulation in forest food webs. The investigators are basing this research on two surprising findings: 1) that methylmercury is high in soils (surprising because forest soils are not anoxic); and 2) that methylmercury is being degraded in soils, and thus the mercury loading is much higher than previously predicted. The proposed work will provide unique training opportunities for undergraduate and graduate students of different academic backgrounds from both the University of North Carolina at Greensboro and the University of Michigan. The principal investigators will integrate this research into classes at both institutions, including field visits and case studies. The principal investigators will also carry out public outreach in the form of a website intended to highlight the findings and impacts of mercury on wildlife to non-scientific audiences.