OCE-PRF Isotopic and microbial investigations of the iron geochemistry and bioavailability of glaciogenic particles

该奖项全部或部分根据2021年美国救援计划法案（公法117-2）资助。微量元素微量营养素，如铁，在海洋生物过程中发挥重要作用。在浮游植物生长并支撑海洋食物网基础的表面沃茨中，铁通常以极低的浓度存在，并且靠近两极，可以限制浮游植物的生产力。受海洋普遍缺铁的影响，微生物已经发展出专门的策略来获取甚至相对不可用的铁矿物质形式，如颗粒物。富含铁的颗粒的一个来源是冰川融水向海洋的输送，随着气候继续变暖，预计这将增加。这项研究旨在研究冰川融化提供的铁与微生物利用这种新铁营养来源的能力之间的关系。为了做到这一点，微生物的生长将在两个受冰川影响严重的沿海地区的冰川冰粒上进行测试：南极洲和阿拉斯加。该项目将支持博士后学者的培训，以及PI参与通过阿拉斯加本土科学工程计划（ANSEP）和斯克里普斯本科生研究奖学金（SURF）计划开展的教育和推广活动，包括在研究项目中指导本科生。 冰川融水由于其高含量的生物可利用铁（Fe），预计将使高纬度海洋肥沃。生物利用度的冰川衍生铁通常推断从大小和化学不稳定性，和以前的调查在生物系统中使用有限数量的铁基板，以探测生物利用度与选择浮游植物物种。仍然需要对海洋环境中冰川铁的获取和生物吸收的机制进行了解。机制的研究，充分表征地球化学和微生物收购的冰川铁有可能大大告知我们的理解之间的耦合相互作用的冰川融水的供应和生态系统的生产力。该提案旨在评估冰川产生的含铁颗粒的生物利用度，结合检查的Fe同位素组成的化学处理的冰川颗粒从离散的冰川冰块与生长实验，使用基因修饰的海洋异养细菌。 本文将对有关冰川颗粒化学不稳定性和生物有效性的两个假说进行研究：1）冰川颗粒的铁稳定同位素特征与化学不稳定性有关，可以用来衡量输运到海洋环境中的沉积物的施肥潜力及其随后的归宿;和2）化学不稳定性可以通过微生物铁获取直接与生物利用度相关，这反过来影响Fe稳定同位素特征。该项目将有助于我们了解海洋微生物群落的哪些成员将受益于冰川铁，铁获取策略在铁同位素特征和海洋系统生物利用度中的作用，该奖项反映了NSF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。

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2).Trace element micronutrients such as iron, play important roles in biological processes in the ocean. In surface waters where phytoplankton grow and support the base of the marine food web, iron is often present at vanishingly small concentrations and near the poles, can limit phytoplankton productivity. Motivated by widespread oceanic iron deficiency, microbes have developed specialized strategies for accessing even relatively unavailable mineral forms of iron, such as particulate matter. One source of iron-rich particles is the delivery of glacial meltwater to the ocean, which is expected to increase as the climate continues to warm. The research proposed here seeks to study the relationships between iron supplied from the melting of glaciers and the ability of microbes to take advantage of this new source of iron nutrition. To do this, the growth of microbes will be tested on glacial ice particles from two coastal locations heavily influenced by glaciers: Antarctica and Alaska. This project will support the training of a postdoctoral scholar, and the participation of the PI in education and outreach activities carried out through the Alaskan Native Science & Engineering Program (ANSEP) and Scripps Undergraduate Research Fellowship (SURF) programs, including mentorship of an undergraduate in a research project. Glacial meltwater is expected to fertilize the high-latitude oceans due to its high content of bioavailable iron (Fe). Bioavailability of glacially-derived Fe is typically inferred from size and chemical lability, and previous investigations in biological systems use a limited number of Fe substrates to probe the bioavailability with select phytoplankton species. A mechanistic understanding of glaciogenic Fe acquisition and biological uptake in marine environments is still needed. Mechanistic studies which fully characterize the geochemical and microbial acquisition of glaciogenic iron have the potential to greatly inform our understanding of the coupled interaction between the supply of glacial meltwater and ecosystems productivity. This proposal seeks to assess the bioavailability of glacially-derived Fe-bearing particles by combining examinations of the Fe isotopic composition of chemically treated glaciogenic particles from discrete glacial ice pieces with growth experiments using a genetically-modified marine heterotrophic bacteria. Two hypotheses regarding chemical lability and bioavailability of glaciogenic particles will be examined in the proposed work: 1) The Fe-stable isotopic signatures of glaciogenic particles are linked to chemical lability, and can be used to gauge the fertilization potential of sediment transported to marine environments and its subsequent fate; and 2) Chemical lability can be directly linked to bioavailability via microbial iron acquisition, which in turn affects Fe-stable isotopic signatures. This project stands to contribute to our understanding of which members of the marine microbial community will benefit from glacially-derived Fe, the role of Fe acquisition strategies in Fe isotopic signatures and bioavailability in marine systems, and the fertilization potential of increased cryospheric weathering inputs to the ocean.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.