Factors Influencing the Rates and Mechanisms of Phytoplankton-Mediated Hydrogen Sulfide Production in Contrasting Oceanic Regimes

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ABSTRACTOCE-0136367The marine chemistry of trace metals, their complexation with ligands, and their interactions with phytoplankton are intimately linked with the cycling of sulfur. In particular trace metal speciation may be profoundly influenced by various forms of reduced sulfur (sulfides), even in the oxygen-rich surface ocean. While sulfides may be produced by the microbial reduction of dissolved sulfate, there is also abundant evidence that some species of phytoplankton may also produce both dissolved and particulate sulfide. In this study, researchers at Old Dominion University will conduct a thorough examination of the rates and mechanisms of hydrogen sulfide production by marine phytoplankton using an iterative laboratory- and field-based approach. They will measure the rates of production of dissolved and particulate sulfide by a number of coastal and oceanic species in continuous culture and examine the influence of variable light, nutrient, and trace metal levels. Additionally they will assess the utility of sulfur isotope measurements in the quantification of biotic and abiotic production of hydrogen sulfide. The laboratory studies will be compared to field measurements. The research team expects to elucidate and quantify the principal mechanisms of production of both dissolved and particulate sulfide and to assess the implications for the cycling of trace metals in surface waters.