Connecting Trace Elements and Metalloenzymes Across Marine Biogeochemical Gradients

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Two scientists from Woods Hole Oceanographic Institution will determine the role of enzymatic activity in the cycling of trace metals. Specifically the researchers would address the following questions: (1) degradation of sinking particulate organic material in the Tropical North Pacific can be influenced by the ability of microbes to synthesize zinc proteases, which in turn is controlled by the abundance or availability of zinc, and (2) methylation of mercury is controlled, in part, by the activity of cobalt-containing enzymes, and therefore the supply of labile cobalt to the corrinoid-containing enzymes or co-factors responsible for methylation. To attain their goal, they will collect dissolved and particulate samples for trace metals and metalloenzymes from three stations along a biogeochemical gradient in the Tropical North Pacific (along 150°W from 18°N to the equator). Sinking particles from metal clean sediment traps will also be obtained. The samples will also be used to carry out shipboard incubation experiments using amendments of metals, metal-chelators, B12, and proteases to examine the sensitivity and metal limitation of heterotrophic, enzymatic degradation of organic matter within the oceanic "Twilight Zone" (100-500 m). This study will result in a novel metaproteomic/metalloenzyme datasets that should provide insights into the biogeochemical cycling of metals, as well as co-limitation of primary productivity and controls on the export of carbon from the photic zone. In terms of broader impacts, an online metaproteomic data server would be created so the community can have access to the raw data files generated by this research. It is anticipated that the current public school outreach activities in Cleveland, Ohio in which the proponents are involved will be continued. During this effort, the proponents plan to use grow-out incubation experiments to teach students about the role of nutrients in phytoplankton growth. One graduate student would be supported and trained by this project.