Collaborative Research: US GEOTRACES GP17-OCE: Size-Fractionated Particle Collection and Analysis from Ultra-Oligotrophic to Antarctic Waters

合作研究：US GEOTRACES GP17-OCE：从超贫营养到南极水域的尺寸分级颗粒收集和分析

• 批准号: 2049297
• 负责人: Phoebe Lam
• 金额: $ 27.82万
• 依托单位: University of California-Santa Cruz
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-08-01 至 2025-07-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2049297&HistoricalAwards=false
• 关键词: Collaborative; Research; US; GEOTRACES; GP17

GEOTRACES is an ongoing international effort to study and understand how low-abundance (“trace”) elements and isotopes are distributed in the world’s oceans. Trace elements include both naturally occurring and human-influenced chemical components of seawater. They have several important roles in the functioning of the Earth that make them a focus of study: 1) their rarity is known to limit the growth of microscopic plants which are the base of ocean food webs; 2) the distributions of trace elements in remote parts of the world show how Earth’s atmosphere, ocean, crust, and ecosystems work together on large, planetary scales; 3) knowledge of these trace components is difficult to acquire but is also an important component to improving computer models of Earth’s climate in a rapidly changing world. The Pacific Ocean covers nearly a third of the planet, and the rarely sampled South Pacific Ocean at the focus of this project includes approximately a quarter of the world’s ocean volume. As part of a GEOTRACES expedition to this remote region, this project has three main goals: 1) to provide the sampling equipment and personnel to collect large volumes of particles from the ocean, because many chemical components in seawater are in particle forms; 2) to document and distribute ocean particle samples to collaborators of many GEOTRACES laboratories; 3) to analyze ocean particles for abundances of approximately two dozen trace elements at laboratories in Savannah, GA and Santa Cruz, CA. A post-doctoral scholar and two graduate students will participate in both field and laboratory aspects of the research.The GP-17 OCE research expedition to the South Pacific Ocean is planned for two months in late 2022 into early 2023. It comprises two transects: a southward transect along approximately 150ºW between French Polynesia and the Southern Ocean which will sample large biological and geochemical gradients from the low-dust, low-biomass oligotrophic sub-tropical gyre, though more productive regions of complex regions of watermass formation and frontal mixing, and into the Southern Ocean. An eastward transect along 67ºS and into Chile will sample the high-opal and Antarctic-influenced Southern Ocean, deep-water hydrothermal influences, and across the South American continental margin. The investigators will use large-volume in-situ pumps to collect size-fractionated particles from the water column which will be distributed to multiple collaborators; and they will operate and maintain particle-sensitive optical equipment to be deployed on the expedition. The research aims to address three main hypotheses: 1) that the large biological gradients from pico-plankton dominated gyre through frontal regions into opal- and Phaeocystis-dominated polar waters will present large gradients in particle export, particle composition, scavenging of trace elements and isotopes (TEIs), and remineralization length-scales of both carbon and TEIs; 2) that particulate iron is dominated by lithogenic (crustally-derived) phases throughout most of the water column, with the exception of regions of strong hydrothermal influence, and that lithogenic particle origins will reflect inputs of external aerosol dust, sediments, hydrothermal sources, and continental inputs as evident via TEI ratios determined after total digestion; 3) that the optical ratio of turbidity to beam attenuation coefficient is sensitive to iron-oxyhydroxide abundances thus acting as a high-resolution indicator of iron-rich authigenic and lithogenic particle inputs.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.

GEOTRACES是一项正在进行的国际努力，旨在研究和了解低丰度（“微量”）元素和同位素在世界海洋中的分布情况。微量元素包括海水中天然存在的和人为影响的化学成分。它们在地球的运作中有几个重要的作用，使它们成为研究的焦点：1）它们的稀有性限制了作为海洋食物网基础的微观植物的生长; 2）世界偏远地区微量元素的分布显示了地球大气，海洋，地壳和生态系统如何在大行星尺度上共同作用; 3）这些微量成分的知识很难获得，但也是在快速变化的世界中改进地球气候计算机模型的重要组成部分。太平洋覆盖了地球近三分之一的面积，而作为该项目重点的南太平洋几乎没有采样，约占世界海洋体积的四分之一。作为GEOTRACES对这一偏远地区考察的一部分，该项目有三个主要目标：1）提供采样设备和人员，从海洋中收集大量颗粒，因为海水中的许多化学成分都是颗粒形式; 2）记录海洋颗粒样品并将其分发给许多GEOTRACES实验室的合作者; 3）在佐治亚州萨凡纳和加利福尼亚州圣克鲁斯的实验室分析海洋颗粒中大约24种微量元素的丰度。一名博士后学者和两名研究生将参与研究的实地和实验室方面。GP-17 OCE研究考察计划于2022年底至2023年初进行两个月的南太平洋考察。它包括两个横断面：沿法属波利尼西亚和南大洋之间约150ºW的沿着向南的断面，将从低尘、低生物量贫营养亚热带环流取样大的生物和地球化学梯度，尽管是水团形成和锋面混合复杂区域的生产力较高的区域，并进入南大洋。沿沿着67ºS向东的样带进入智利，将对高蛋白石和受舌状岩影响的南大洋、深水热液影响以及整个南美大陆边缘进行采样。研究人员将使用大容量原位泵从水柱中收集尺寸分级的颗粒，这些颗粒将被分配给多个合作者;他们将操作和维护将部署在探险队中的颗粒敏感光学设备。本研究旨在解决三个主要假设：1）从微微型浮游生物占主导地位的环流通过锋面区域进入蛋白石和棕囊藻占主导地位的极地沃茨的大生物梯度将在颗粒输出、颗粒组成、痕量元素和同位素（TEI）清除以及碳和TEI的再矿化长度尺度上呈现大的梯度; 2）颗粒铁以岩石成因为主（地壳衍生）阶段贯穿大部分水柱，但热液影响强烈的区域除外，而成岩颗粒的来源将反映外部气溶胶尘埃、沉积物、热液源和大陆输入，通过总消化后确定的TEI比率证明; 3）浊度与光束衰减系数的光学比率对铁-羟基氧化物丰度敏感，因此充当铁-羟基氧化物的高分辨率指示剂。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的学术价值和更广泛的影响审查标准。