U.S.-Brazil Planning Visit: Facilitating Collaborative Research on the Southern Brazilian Continental Shelf

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The southern Brazilian continental shelf is the site of important marine fisheries, supporting economic resources for Brazil, Uruguay and Argentina. Regional population growth is expected to result in continued development of coastal areas along the shelf therefore prudent resource management requires a comprehensive assessment of present day conditions. Changes in the flux and sources of nutrients supporting the base of the regional food web could upset these economically important fisheries. Nutrients are transported into this area through outflow of the Rio de la Plata and the Patos Lagoon as well as submarine groundwater discharge but the relative contribution of nutrients and trace metals from each of these sources remains unknown. This project will support travel for three early-career U.S. investigators to establish an international collaboration with Brazilian researchers. During the visit, the U.S. research team will conduct meetings, seminars and field trips to gather regionally-relevant information. The outcome of this planning visit will be the development of an international collaborative research plan to investigate biogeochemical cycling along the southern Brazilian continental shelf. Recent evidence suggests that submarine groundwater discharge contributes a substantial amount of nutrients and trace metals (especially iron) to the coastal waters of this region but the importance of this source relative to surface outflows (e.g., Rio de la Plata plume and Patos Lagoon drainage) remains unknown. Seasonally-varying coastal currents likely disperse biogeochemically-relevant constituents differently therefore this visit will involve planning how to investigate the potential use of various water mass tracers to characterize the sources and transport mechanisms across the continental shelf. The planning work will involve developing an international collaboration to address the following questions: 1) What are the relative contributions of the Plata Plume, Patos Lagoon and submarine groundwater discharge of freshwater, nutrients and trace metals to the southern Brazilian continental shelf as determined by water mass tracers? 2) What is the seasonal effect of these sources on coastal water column dissolved and particulate trace element chemistry along the southern Brazilian continental shelf? 3) Is there a significant leachable particulate trace metal fraction available for deposition on the shelf and supply micro-nutrients during upwelling? 4) What are the characteristics of Fe-binding ligands associated with plume waters? 5) Are iron isotopic signatures useful for quantifying processes in the Plata plume system? The future proposal from this group will have results extending to larger research programs such as GEOTRACES. The planning visit will foster an international collaboration between Brazilian and U.S. researchers, and will allow a U.S. Ph.D. student to gain international experience in research project development including hypothesis formulation, objective defining and methodology verification.