Collaborative Research: A multidimensional approach to understanding microbial carbon cycling beneath the seafloor during cool hydrothermal circulation

全球海洋包括地球上最大的微生物组，至少有一半的海洋微生物生物量存在于海底之下。特别是，海洋地壳包含地球上最大的含水层，其液体体积约等于海洋体积的2%。它还拥有大量的微生物生命，可能会影响全球规模的生物地球化学循环。该项目研究地球上最大的活跃流动含水层系统-通过海洋和沉积物下的海洋地壳循环的流体。尽管有关深海生命的知识不断进步，但对岩石海洋地壳中的微生物和流经其中的流体的理解仍然很原始。该项目的重点是了解微生物活动与凉爽海底下生物圈中碳循环之间的联系。将利用国际海洋发现计划在大西洋中脊两侧建立的海底观测站来确定地壳生物圈内消耗有机碳和产生有机碳的新陈代谢之间的平衡，大西洋中脊可能代表了全球热液循环的大部分。微生物转化碳的速率将使用地球化学和生物学方法来确定。研究结果将有助于确定海底微生物介导的过程在多大程度上影响海洋中的碳循环。这项工作将代表在寒冷的含氧地壳含水层的碳循环的第一个全面的描述。两名女性博士后将获得资助，高中和社区大学的学生也将通过与科德角社区学院和剑桥-林奇和拉丁学校的合作参与其中。其目标是通过实践研究经验、同行指导和专业发展机会，促进高中和社区大学学生的科学、技术、工程和数学素养。该项目的目标是回答这个问题：“冷地壳海底下生物圈是净自养还是净异养？”“这项工作的重点是北池，这是一个孤立的沉积池，位于大西洋中脊西侧700万至800万年前的海脊侧翼洋壳上。该项目的两个目标是：1。描述海底流体中悬浮颗粒的无机和有机碳含量以及天然14 C和13 C同位素比率，以确定微生物介导的通量和过程。说明与颗粒有关的和自由生活的微生物群落对海底下流体初级生产和矿化的净影响，同位素地球化学和分子生物学方法的结合是一个重要的交叉研究，在了解年轻洋壳海底下生物圈的微生物生态学和地球化学方面的学科进展维持全球深海氧化还原平衡。预期成果包括确定与颗粒相关和自由生活的海底下微生物群落中的自养和异养代谢特征，以及对自养和异养代谢和相关分类丰度进行量化，以深入了解地壳流体中碳通量的净和特定微生物过程。

The global ocean comprises Earth's largest microbiome, with at least half of the ocean's microbial biomass occurring beneath the ocean floor. In particular, oceanic crust encompasses the largest aquifer on Earth, with a liquid volume equal to approximately 2% of the ocean's volume. It also harbors a substantial reservoir of microbial life that may influence global-scale biogeochemical cycles. This project investigates this largest actively flowing aquifer system on Earth- the fluids circulating through oceanic crust underlying the oceans and sediments. Despite advancing knowledge about life in the deep ocean, the understanding of microorganisms in the rocky oceanic crust and the fluids flowing through it remains rudimentary. This project is focused on understanding the linkages between microbial activity and the cycling of carbon in the cool, subseafloor biosphere. The balance between organic carbon-consuming and organic carbon-producing metabolisms within the crustal biosphere will be determined using seafloor observatories put in place by the International Ocean Discovery Program (IODP) on the flanks of the Mid-Atlantic Ridge, likely representative of the majority of global hydrothermal fluid circulation. The rates of microbial transformations of carbon will be determined using both geochemical and biological approaches. Results will help establish the extent to which microbially-mediated processes in the subseafloor influence carbon cycling in the ocean. This work will represent the first comprehensive description of carbon cycling in the cold oxic crustal aquifer. Two female postdocs will be supported on the grant, and both high school and community college students will also be involved through collaborations with Cape Cod Community College and Cambridge-Rindge and Latin School. The goal is to promote science, technology, engineering and math literacy among high-school and community college students through hand-on research experiences, peer-to-peer mentoring, and professional development opportunities. The goal of the project is to answer the question "is the cool crustal subseafloor biosphere net autotrophic or net heterotrophic?" The focus of the effort is at North Pond, an isolated sediment pond located on ridge flank oceanic crust 7-8 million years old on the western side of the Mid-Atlantic Ridge. The two objectives of the project are to:1. Characterize suspended particles in subseafloor fluids with respect to their inorganic and organic carbon content, and natural 14C and 13C isotopic ratios, to determine microbially-mediated fluxes and processes.2. Characterize the net influence of particle-associated and free-living microbial communities on subseafloor fluid primary production and remineralization, as well as the taxon-specific contributions to these same processes.The integration of isotope geochemical and molecular biological approaches represents a significant cross-disciplinary advance in the understanding of the microbial ecology and geochemistry of the subseafloor biosphere in young oceanic crust and their role in maintaining global deep-sea redox balance. Expected outcomes include identifying signatures of autotrophic and heterotrophic metabolism in particle-associated and free-living subseafloor microbial communities as well as quantification of autotrophic and heterotrophic metabolism and associated taxon-abundances to provide insights into the net and specific microbial processes in crustal fluids on carbon fluxes.