Processes Affecting the Speciation of Iodine in the Oceans

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Iodine occurs in seawater as iodate, iodide and organic iodine. Although iodine is the most abundant biophilic minor element and the distributions of its inorganic forms are known, direct evidence concerning the processes that may control its speciation is largely incomplete. The uptake of dissolved iodine species and the accompanying reduction of iodate to iodide by marine organisms may be similar to and/or intertwined with the uptake of nitrogen species which is a major controlling factor of marine primary production. Iodide is the most abundant inorganic reducing agent in surface seawater. The reactions between iodide and oxidizing trace species can have geochemically important implications on marine as well as global tropospheric chemistry. The overall goal of this project is to understand and quantify the biological and biological processes that control the speciation of iodine in seawater and the interactions of the iodine system with other geochemically important species. The investigation will (1) quantify the uptake of dissolved iodine species by phytoplankton, test the interactions between the iodine and nitrogen systems in the process and evaluate the possibility of using iodate as a convenient analog for studying nitrate uptake; and (2) quantify the reactions between iodide and hydrogen peroxide in seawater and estimate the importance of these reactions to the marine geochemistry of the iodine system.