US GEOTRACES GP17-OCE and GP17-ANT: Particulate and biogenic trace elements in the South Pacific and Southern Ocean

国际GEOTRACES计划的目标是了解微量化学元素及其同位素在海洋中的分布。许多微量金属，如铁、锰和锌，是生命所必需的，也是浮游植物的营养物质。然而，太平洋和南大洋地区的铁和锰浓度非常低，有时限制了浮游植物的生长。该项目将增进对这些区域浮游植物吸收和去除微量营养元素金属的了解。该项目将完成三个主要目标：1）测量从塔希提岛到智利的航行期间从南太平洋和南大洋上部区域收集的颗粒中磷和11种痕量金属的浓度; 2）直接测量从这些沃茨收集的浮游植物细胞中这些元素的一个子集，沿着碳、硫和硅;和3）测量在随后的阿蒙森海的同伴巡航中从南极沿海沃茨收集的浮游植物中的相同元素。两名本科生实习生将参与该项目，沿着还有一名博士后学者。科学成果和研究经验将通过两个班级与其他本科生分享，该项目将通过虚拟现实游戏和项目期间制作的相关活动以及通过图书馆和机构外展活动介绍给更广泛的公众。美国GEOTRACES GP 17-OCE探险计划于2022年底，目的是确定沿着一条对全球养分和碳循环具有重要意义的区域的断面的微量元素和同位素分布，该断面穿越南太平洋环流、南极绕极流的铁限制沃茨、具有热液输入的太平洋深水沃茨，和智利边缘附近的沃茨。南太平洋环流和南大洋的太平洋部分是全球海洋内热量、碳和营养物质转移的气候关键区域，它们是浮游植物生长通常受到海洋表层低浓度铁（Fe）限制的区域。研究人员将使用电感耦合等离子体质谱和同步辐射X射线荧光显微镜来解决三个主要的研究问题，集中在该地区的微量元素的内部地球化学循环：1）主要浮游植物类群的微量元素含量如何响应环境常量营养素和微量元素梯度？2)不同颗粒物组分（岩源、自生、生物源）的微量元素组成在剖面上如何变化？3)颗粒物质的组成和化学计量如何影响周围水体的微量元素循环和微量元素：营养物质的化学计量？该奖项反映了NSF的法定使命，并被认为是值得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的支持。

The goal of the international GEOTRACES program is to understand the distributions of trace chemical elements and their isotopes in the oceans. Many trace metals, such as iron, manganese and zinc, are essential for life and serve as nutrients for phytoplankton. However, regions of the Pacific and Southern Oceans have very low concentrations of iron and manganese, in particular, limiting the growth of phytoplankton at times. This project will improve understanding of the uptake and removal of micronutrient metals by phytoplankton in these regions. This project will accomplish three main objectives: 1) measure the concentrations of phosphorus and eleven trace metals in particles collected from the upper region of the South Pacific and Southern Oceans during a cruise from Tahiti to Chile; 2) measure a subset of these elements, along with carbon, sulfur and silicon, directly in phytoplankton cells collected from these waters; and 3) measure the same elements in phytoplankton collected from coastal Antarctic waters on a subsequent, companion cruise into the Amundsen Sea. Two undergraduate student interns will be involved in the project, along with a postdoctoral scholar. The scientific results and research experience will be shared with additional undergraduates through two classes, and the project will be brought to the broader public through a virtual reality game and associated activities produced during the project and introduced through libraries and institutional outreach events.The U.S. GEOTRACES GP17-OCE expedition, planned for late 2022, aims to determine the distribution of trace elements and isotopes along a transect spanning regions of global importance to nutrient and carbon cycling, crossing the South Pacific Gyre, the iron-limited waters of the Antarctic Circumpolar Current, Pacific Deep Waters with hydrothermal inputs, and waters near the Chilean margin. The South Pacific Gyre and Pacific sector of the Southern Ocean are climate-critical regions for the transfer of heat, carbon, and nutrients within the global ocean, and they are a region where phytoplankton growth is typically limited by low concentrations of iron (Fe) in the surface ocean. The researchers will use inductively-coupled plasma mass spectrometry and synchrotron x-ray fluorescence microscopy to address three primary research questions focused on the internal biogeochemical cycling of trace elements in this region: 1) How do trace element contents of dominant phytoplankton taxa respond to environmental macronutrient and trace element gradients? 2) How does the trace element composition of the various particulate matter fractions (lithogenic, authigenic, biogenic) vary across the section? 3) How does the composition and stoichiometry of particulate material influence trace element cycling and trace element:nutrient stoichiometry of the surrounding water masses?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.