Collaborative Research: U.S. GEOTRACE GP17-OCE and GP17-ANT: Characterizing iron-binding organic ligands in the Southern Ocean and implications for iron cycling in the global ocean

铁是生命所必需的元素，在确定浮游植物将多少大气中的二氧化碳吸收到海洋中起着重要作用。然而，铁的循环受到海水化学的密切控制；海水中几乎所有的铁都与各种未知的有机化合物有关，这些化合物被称为铁结合配体，影响生物是否以及如何利用铁以及铁在海洋中的分布。详细了解有机铁结合配体的循环对于了解海洋中的铁循环以及铁循环与大气碳之间的联系是必要的。这项拟议的研究将作为美国GEOTRACES探险的一部分进行，以检验以下假设：南大洋是全球重要的铁结合有机配体来源，这些有机分子的不同来源导致不同的铁配体特征。美国的GEOTRACES计划是一项大规模的合作努力，旨在以高分辨率对海洋系统进行一系列关键微量元素和同位素的采样。即将到来的美国GEOTRACES GP17巡航所针对的南太平洋和南大洋地区是水团形成和随后向全球海洋输送碳和营养物质的重要地点。因此，在这些区域产生的有机配体对铁沿全球水团循环路径的稳定性、反应性和停留时间具有重要影响，并可能影响全球海洋溶解铁的清单。该项目将测量铁结合有机配体的分布，并确定组成这些配体的特定有机分子，以及在即将在南太平洋(GP17-OCE)和南大洋(GP17-ANT)收集的美国GEOTRACES邮轮上收集的现场和实验样本。这些数据集将被用来对表征铁结合有机配体的两种最广泛使用的方法进行首次广泛的相互校准，提供对这些数据集以及如何合成它们以改进对海洋中铁循环的理解的重要见解。该项目的所有数据都将向公众开放。项目活动将为初中生、高中生、本科生和研究生提供教育和培训机会，结果将通过虚拟现实模块的开发和当地的外展活动与公众分享。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Iron is an essential element for life and plays an important role in defining how much atmospheric carbon dioxide is taken up into the ocean by phytoplankton. However, iron cycling is closely governed by the chemistry of seawater; nearly all iron in seawater is associated with various unknown organic compounds, called iron-binding ligands, which impact whether and how iron is utilized by organisms and the distribution of iron throughout the ocean. Detail understanding of the cycling of organic iron-binding ligands is necessary to understand iron cycling in the oceans and the connections between iron cycling and atmospheric carbon. The proposed research will be carried out as a part of US GEOTRACES expedition to test the hypothesis that the Southern Ocean is a globally significant source of iron-binding organic ligands, and that different sources of these organic molecules lead to different iron-ligand characteristics. The US GEOTRACES program is a large collaborative effort to sample ocean systems at high resolution for a suite of key trace elements and isotopes. The South Pacific and Southern Ocean regions targeted by the upcoming US GEOTRACES GP17 cruises are important locations of water mass formation and the subsequent transport of carbon and nutrients to the global ocean. Organic ligands produced in these regions thus have important implications for the stabilization, reactivity, and residence time of iron along the path of global water mass circulation and could impact the global oceanic inventory of dissolved iron. This project will measure the distribution of iron-binding organic ligands, and identify specific organic molecules that comprise these ligands, in field and experimental samples collected on upcoming US GEOTRACES cruises in the South Pacific (GP17-OCE) and Southern Ocean (GP17-ANT). These datasets will be utilized to conduct the first extensive intercalibration of the two most widely used approaches for characterizing iron-binding organic ligands, providing important insight into these datasets and how they can be synthesized to improve understanding of iron cycling in the oceans. All data from this project will be made publicly available. Project activities will provide educational and training opportunities for middle school, high school, undergraduate, and graduate students, and results will be shared with the public through the development of virtual reality modules and via local outreach events.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.