Atmospheric and Lateral Inputs of Trace Metals in the Indonesian Through-Flow

南蓝鳍金枪鱼（SBT）的产卵地位于澳大利亚西北海岸和印度尼西亚之间。来自太平洋的水以印度尼西亚通流（ITF）的形式流经东南亚岛屿，流入西印度洋。ITF中的营养条件不足以支持SBT幼虫的最佳摄食和生长，营养循环和食物链之间的许多联系仍然未知。该地区的主要和微量营养物质，如氮、磷和铁，都很少有测量结果。这些营养物质支持浮游植物，形成食物链的基础，并影响更高的营养水平，包括SBT。这项工作将调查该地区主要和次要营养物质的潜在来源，包括岛屿输入、澳大利亚沙尘、季风降雨和沉积通量，这将有助于制定“营养预算”，并揭示哪些来源对SBT早期生命阶段的成功贡献最大。该项目是美国对第二次国际印度洋考察（IIOE-2）的贡献，将促进对研究较少的东印度洋生物地球化学和生态动力学的理解。该项目将支持一名早期职业博士后研究员，外展活动将包括参加开放日活动和REU在国内机构的暑期项目。在通过东南亚岛屿海峡的过程中，ITF的主要和微量营养物质的分布可能发生潜在的变化。沿海洋流可以使含有Si和Fe等营养物质的陆架沉积物重新悬浮起来，而来自澳大利亚和东南亚的自然和人为物质的大气沉降可以提供N、P、Fe和其他微量金属。季风雨也通过气溶胶和径流的湿沉积提供养分。这些输入将营养物质引入ITF的表层海洋，浮游植物可以将无机营养物质转化为生物量，进而为整个食物链提供燃料。在这项研究中，气溶胶和水柱痕量金属将被调查，作为另一个nsf资助的BLOOFINZ项目的补充组成部分，该项目旨在了解南方蓝鳍金枪鱼产卵场的N循环和食物网动态。提出的研究将解决三个假设：（H1） ITF从干湿大气沉积和再悬浮沉积物中接收生物活性微量元素的输入，（H2）通过南赤道流（SEC）将这些营养物质运输到印度洋。（H3）矿物沉积和人为气溶胶或大陆架对铁的输入有助于缓解ITF的N限制。为了研究这些假设并了解ITF中微量金属的输入、移除和循环，将对气溶胶和海洋溶解相和颗粒相中的物质浓度、元素比例和通量进行量化和比较。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The spawning grounds of the Southern Bluefin Tuna (SBT) lie between the northwestern Australian coast and Indonesia. Waters from the Pacific flow through Island Southeast Asia as the Indonesian Through-Flow (ITF) and into the western Indian Ocean. Nutrient conditions in the ITF are insufficient to support optimum feeding and growth of SBT larvae, and numerous links between the nutrient cycles and food chain remain unknown. There are very few measurements of both major and trace nutrients like nitrogen, phosphorus, and iron made in the region. These nutrients support phytoplankton that form the base of the food chain and affect higher trophic levels, including SBT. This work will investigate the potential sources of major and minor nutrients to the region, including island inputs, Australian dust, monsoon rains, and sedimentary fluxes which will help develop a “nutrient budget” and reveal which sources contribute the greatest to the success of early SBT life stages. This project is a US contribution to the 2nd International Indian Ocean Expedition (IIOE-2) that will advance understanding of biogeochemical and ecological dynamics in the poorly studied eastern Indian Ocean. The project will support an early career postdoctoral researcher and outreach activities will include participation in Open House events and REU summer program at home institution.The ITF can undergo potential changes to the distributions of major and trace nutrients during passage through the straits of southeast island Asia. Coastal currents can resuspend shelf sediments containing nutrients like Si and Fe, while the atmospheric deposition of both natural and anthropogenically derived material from Australia and southeastern Asia can supply N, P, Fe, and other trace metals. Monsoon rains also supply nutrients via wet deposition of aerosols and runoff. These inputs introduce nutrients to the surface ocean of the ITF, where phytoplankton can convert inorganic nutrients to biomass and in turn fuel the entire food chain. In this research aerosols and water column trace metals will be investigated, as a complementary component to another NSF-funded BLOOFINZ project which seeks to understand the N cycling and food-web dynamics of the southern bluefin tuna spawning grounds. The proposed research will address three hypotheses: (H1) The ITF receives inputs of bioactive trace elements from wet and dry atmospheric deposition and resuspended sediments, and (H2) transports these nutrients across the Indian Ocean via the South Equatorial Current (SEC). (H3) Inputs of Fe from atmospheric deposition of mineral and anthropogenic aerosols or continental shelves could help alleviate N limitation in the ITF. To investigate these hypotheses and understand the inputs, removals, and cycles of trace metals in the ITF, the concentrations, elemental ratios, and fluxes of material in aerosols and marine dissolved and particulate phases will be quantified and compared.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.