Fe Behavior and Bioavailability in Sub-aerial Runoff into the Ross Sea

浮游植物，或微小的海洋藻类，是碳循环的重要组成部分，可以通过将大气中的碳转移到海洋中来降低大气中二氧化碳的排放速率。南大洋浮游植物的密度经常受到海洋铁供应的限制。这反过来又会影响碳从大气向海洋转移的速度。南大洋铁的主要来源是被侵蚀的大陆岩石。了解由于陆地冰川融化增加而进入南大洋的铁的当前和未来来源，对于预测未来南大洋浮游植物的密度和随后对碳循环的影响是必要的。南大洋铁的一个鲜为人知的来源是来自无冰地区的水流输入，例如南极洲的麦克默多干谷。如果冰川退缩，这种铁的来源可能会变得更大。这项研究调查了麦克默多干谷溪流直接进入南大洋的铁的来源和数量。由于并非所有形式的铁都可以被浮游植物利用，因此将进行实验，以确定浮游植物对铁的利用率，以及铁与海水的混合情况。该项目成果的360度身临其境的视频、信息图表和教育视频将在社交媒体、学校和科学活动以及城市科学中心共享。在南大洋(SO)，常量营养素过剩，但由于铁的原因，区域初级生产受到限制或共同限制。向海洋中添加铁将影响生物化学循环，增加初级生产力，并影响SO中浮游植物群落的结构和组成。铁到SO的通量在全球范围内是显著的，因为增加的铁肥会导致碳封存的增加，这对大气中二氧化碳的增加起到了负反馈的作用。南极沿海地区潜在的生物可利用铁的一个来源是南极洲无冰地区的直接空中水流排放，如果陆地冰川消退，这个来源可能会变得更加重要。如果要开发更好的碳循环和大气化学预测模型，就必须了解铁的来源、性质、潜在的命运和对SO的通量。该项目将研究控制溶解铁流入罗斯海的流中过程和特征，包括光还原、温度和与有机物的络合作用。这项新的研究将量化南极洲排入SO的溪流中颗粒铁的生物有效性和溶解铁的生物有效性。将对溶解的铁物种进行现场形态测量，使用高分辨率光谱分析确定颗粒铁的形态，将与沿海海水进行混合实验，并将通过海洋生物分析确定铁的生物有效性。该项目将为两名学生提供宝贵的南极实地经验，并通过与K-12学校的现有合作伙伴关系、公共STEM活动、一个城市科学中心和强大的社交媒体存在，接触到数千名个人。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。

Phytoplankton, or microscopic marine algae, are an important part of the carbon cycle and can lower the rates of atmospheric carbon dioxide by transferring the atmospheric carbon into the oceans. The concentration of phytoplankton in the Southern Ocean is regularly limited by the availability of marine iron. This in turn influences the rate of carbon transfer from the atmosphere to the ocean. The primary source of iron in the Southern Ocean is eroded continental rock. Understanding the current and future sources of iron to the Southern Ocean as a result of increased melting of terrestrial glaciers is necessary for predicting future concentrations of Southern Ocean phytoplankton and the subsequent influence on the carbon cycle. A poorly understood source of iron to the Southern Ocean is stream input from ice-free regions such as the McMurdo Dry Valleys in Antarctica. This source of iron is likely to become larger if glaciers retreat. This study investigates the sources and amount of iron transported by McMurdo Dry Valley streams directly into the Southern Ocean. Because not all forms of iron can be used by phytoplankton, experiments will be performed to determine how available iron is to phytoplankton and how iron mixes with seawater. Immersive 360-degree video, infographics, and educational videos of findings from this project will be shared on social media, at schools and science events, and in an urban science center.In the Southern Ocean (SO) there is an excess of macronutrients but regional primary production is limited or co-limited due to iron. An addition of iron to the ocean will affect biochemical cycles, increase primary production, and affect the structure and composition of phytoplankton communities in the SO. Iron flux to the SO is globally significant, as increased Fe fertilization leads to increased carbon sequestration which acts as a negative feedback to increased atmospheric pCO2. One source of potentially bioavailable iron to the coastal regions of the SO is from direct sub-aerial stream discharge in ice-free areas of Antarctica, a source that may become more important if terrestrial glaciers retreat. It is imperative to understand the source, nature, potential fate, and flux of iron to the SO if better predictive models for the carbon cycle and atmospheric chemistry are to be developed. This project will investigate in-stream processes and characteristics controlling dissolved iron draining into the Ross Sea including photoreduction, temperature, and complexation with organic matter. The novel study will quantify bioavailability of particulate iron and bioavailability of dissolved iron in Antarctic in streams draining into the SO. On-site speciation measurements will be performed on dissolved iron species, particulate iron speciation will be determined using high-resolution spectroscopy, mixing experiments will be performed with coastal marine water, and the bioavailability of Fe will be determined through marine bioassays. This project will provide two students with valuable Antarctic field experience and reach thousands of individuals through existing partnerships with K-12 schools, public STEM events, an urban science center, and a strong social media presence.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.