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

巴西南部大陆架是重要的海洋渔业基地，为巴西、乌拉圭和阿根廷提供经济资源。预计区域人口增长将导致沿大陆架沿海地区的持续发展，因此谨慎的资源管理需要对目前的情况进行全面评估。支持区域食物网基础的营养物质的流量和来源的变化可能会扰乱这些经济上重要的渔业。营养物质通过拉普拉塔河和帕托斯泻湖的流出以及海底地下水的排放被输送到这一地区，但这些来源的营养物质和微量金属的相对贡献仍然未知。该项目将资助三名早期美国研究人员与巴西研究人员建立国际合作关系。在访问期间，美国研究小组将举行会议、研讨会和实地考察，以收集与地区有关的信息。这次规划访问的结果将是制定一项国际合作研究计划，以调查巴西南部大陆架的生物地球化学循环。最近的证据表明，海底地下水排放为该地区的沿海水域贡献了大量的营养物质和微量金属（特别是铁），但这一来源相对于地表流出（例如，里约热内卢de la Plata羽流和Patos Lagoon排水）的重要性仍然未知。季节性变化的沿海洋流可能以不同的方式分散生物地球化学相关成分，因此这次访问将涉及规划如何调查各种水团示踪剂的潜在用途，以表征其来源和跨大陆架的运输机制。规划工作将涉及开展一项国际合作，以解决以下问题：1)通过水团示踪剂确定，普拉塔柱、帕托斯泻湖和海底地下水向巴西南部大陆架排放的淡水、营养物和微量金属的相对贡献是什么？2)这些污染源对巴西南部大陆架沿海水体溶解和颗粒微量元素化学的季节性影响是什么？3)在上涌过程中，是否有大量可浸出的微量金属颗粒沉积在陆架上并提供微量营养物质？4)与羽流水体相关的铁结合配体的特征是什么？5)铁同位素特征对Plata羽流系统的量化过程有用吗？这个小组未来的建议将会扩展到更大的研究项目，如GEOTRACES。这次计划中的访问将促进巴西和美国研究人员之间的国际合作，并将使一名美国博士生获得研究项目开发方面的国际经验，包括假设制定、客观定义和方法验证。

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.