Award: OCE-1130549

This project contributed to the development of a global 3-D model for mercury cycling in the oceans (Figure 1) and a preliminary model for the global air-sea exchange of selenium. Our research provided insight into factors controlling the reactivity and loss of mercury from the ocean to the atmosphere, as well as factors driving uptake of the neurotoxic and bioaccumulative species, methylmercury. We found that the fraction of elemental mercury in surface waters is highest in offshore waters and this is correlated with a higher fraction of degraded terrestrial organic matter. Marine dissolved organic matter appears to have little impact on uptake of methylmercury by cells but terrestrial dissolved organic matter can inhibit uptake at high concentrations. We also measured for the first time active production of the bioaccumulative species, methylmercury, in oxic estuarine seawater. Understanding these processes is important for anticipating the effects of future climate-driven changes in freshwater discharges on contaminants such as methylmercury in marine food webs. This work has more broadly contributed to a 3-D biogeochemical modeling capability for persistent global contaminants that is available to the global community of GEOS-Chem and MITgcm users. This research was also used to inform the negotiations of the global Minamata Convention for controlling anthropogenic mercury released led by the United Nations Environment Programme in 2013. Last Modified: 11/29/2015 Submitted by: Elsie M Sunderland