OCE-PRF: Biomediated corrosion of methane-derived authigenic carbonates in the deep ocean and its implications for carbon fluxes from methane seeps

该研究会调查生物过程释放回海水的碳量，这些生物过程溶解了海洋甲烷渗漏形成的碳酸盐岩石结构。在整个世界的海洋中，甲烷通过俯冲带的海底沉积物和埋在海底下面的旧有机物质上升。这些甲烷中的大部分在到达海洋或大气之前被独特的微生物和化学活动所消耗。在这个“甲烷圈”中，岩石在海底附近的软沉积物中溶解时形成，或者从下面渗出的气态碳以固体碳酸盐的形式沉淀。这些岩石为深海生物栖息和储存碳提供了一个坚硬的表面，否则碳会导致海洋和大气中二氧化碳的增加。当周围水域的酸含量增加时，碳酸盐会溶解回海水中，这可能是碳酸盐岩及其周围发生的复杂生物地球化学反应造成的。如果不考虑碳酸盐的这种溶解，就不能完全量化与人为气候变化相关的时间尺度上从海底进入大气的碳的数量。这项研究将支持两名本科生，并提供地理信息系统、图像处理软件、数据库管理以及同行评议手稿开发和出版方面的培训。除了为加州大学洛杉矶分校的本科生提供培训外，调查人员还与阿拉斯加原住民科学与工程项目和SoCalSeas合作。SoCalSeas是南加州的教师网络，由来自两年制和四年制大学的教师组成，旨在衔接海洋学教育。该项目的成果将作为各种学习方式的各种媒体内容传播给公众和学术团体，包括加州大学洛杉矶分校的科学多样化领导中心，旨在宣传和鼓励人们参与深海科学及相关领域。例如，这个项目的海底地图将适用于高中、社区大学和大学课堂教学的地理信息系统练习。虽然NSF资助的METHANOSPHERE项目旨在重新定义深海甲烷渗漏对底栖生态系统的足迹，但没有讨论生物中介碳酸盐腐蚀的作用。这项研究的目的是通过U系列年表直接评估与腐蚀驱动的自生碳酸盐溶解有关的一段时间内的碳损失；通过U系列年代学确定碳酸盐的年代；接种活微生物的碳酸盐培养，以确定与不同微生物腐蚀过程相关的碳通量；扫描电子显微镜，以量化碳酸盐表面腐蚀并确定其来源；以及将这些结果与相关的METHANOSPHERE项目结果相结合的地球化学模拟，以计算典型深海条件下生物中介碳酸盐腐蚀随时间的碳损失。METHANOSPHERE地点将允许比较甲烷生成的自生碳酸盐在氧气水平较高但光合作用食物输入较低(阿留申)和氧气较低但生产率较高(加利福尼亚州)的典型条件下的腐蚀情况。将计算与这些地点的碳酸盐腐蚀相关的碳通量，并将其与负责估计与给定环境和腐蚀过程相关的通量的生物体联系起来。这项研究的目标是产生1。)南加州边界地区渗漏的侵蚀物质平衡，包括实验数据、海底光子学和底物地图，2。阿留申边缘渗漏的侵蚀物质平衡，包括实验数据、海底光学学和底物图，以及3.甲烷来源的自生碳酸盐腐蚀模式识别指南(包括两个地点的数据)。研究人员正在通过船上和实验室的培养和分析对碳酸盐进行调查、采样和表征，以实现这些目标。这项研究的见解将至少每年在一个国际会议上发表一次；作为加州大学洛杉矶分校大一新生班的客座讲座，面向非STEM学生，以及本科生/研究生课程“水生地球微生物学”。由于甲烷渗漏和残留碳酸盐在大陆边缘广泛存在，渗漏碳酸盐中的碳循环可能是全球海底甲烷预算的重要组成部分，其量化对于估计甲烷衍生碳的长期埋藏至关重要。这一奖项反映了NSF的法定使命，通过使用基金会的智力优势和更广泛的审查标准进行评估，被认为值得支持。

This research fellowship investigates the amount of carbon released back into seawater by biological processes that dissolve the carbonate rock structures formed at oceanic methane seeps. Throughout the worlds’ oceans, methane rises through seafloor sediments from subduction zones and old organic material buried below the seafloor. Most of this methane is consumed by unique microbial and chemical activity before it can reach the ocean or atmosphere. Within this “methanosphere”, rocks form in the soft sediments near the seafloor when dissolved or gaseous carbon seeping up from below precipitates as solid carbonate. These rocks provide a hard surface for deep-sea organisms to inhabit and store carbon that would otherwise contribute to increased carbon dioxide in the ocean and atmosphere. Carbonate will dissolve back into seawater when the acid content of surrounding waters increases, which can be caused by the complicated biogeochemical reactions occurring on and around the carbonate rocks. Without accounting for this dissolution of carbonate, the amount of carbon that reaches the atmosphere from the subseafloor on timescales relevant to anthropogenic climate change cannot be fully quantified. This research will support two undergraduates and provide training in Geographic Information Systems; image processing software; database management; and peer-reviewed manuscript development and publication. In addition to training for undergraduate students at UCLA, the investigators are collaborating with the Alaska Native Science and Engineering Program and SoCalSeas, the Southern California network of teachers from 2-year and 4-year colleges designed to bridge education in oceanography. Results of the project will be disseminated to public and academic groups, including the Center of Diverse Leadership in Sciences at UCLA, as a variety of media content for a range of learning styles designed to inform and inspire participation in deep-sea science and related fields. For example, the seafloor maps from this project will be adapted to GIS exercises for high school, community college, and university classroom instruction.While the NSF-funded METHANOSPHERE project aims to redefine the footprint of deep ocean methane seepage for benthic ecosystems, the role of biomediated carbonate corrosion is not addressed. This study aims to directly evaluate the carbon loss over time associated with corrosion-driven dissolution of methane derived authigenic carbonate through U-series chronology to date carbonates; incubation of carbonates inoculated with living microbes to determine the carbon flux associated with different microbiological corrosion processes; scanning electron microscopy to quantify carbonate surface corrosion and identify its source; and geochemical modeling that combines these results with the relevant METHANOSPHERE project results to calculate the carbon loss over time from biomediated carbonate corrosion under canonical deep ocean conditions. The METHANOSPHERE sites will allow the comparison of methane derived authigenic carbonate corrosion under the representative conditions of higher oxygen levels with lower photosynthetic food input (Aleutian) and lower oxygen with higher productivity conditions (California). Carbon fluxes associated with carbonate corrosion at these sites will be calculated and related to the organisms responsible to estimate a flux associated with a given environment and corrosion process. The goals of this study are to produce 1.) An erosion mass balance of the Southern California Borderlands Seep, including experimental data, seafloor photomosaics, and substrate maps, 2.) An erosion mass balance of the Aleutian Margin Seep including experimental data, seafloor photomosaics and substrate maps, and 3.) A methane derived authigenic carbonate corrosion pattern identification guide (including data from both sites). The investigators are addressing these goals by surveying, sampling, and characterizing carbonates through shipboard and laboratory incubations and analyses. Insights from the study will be presented at least once annually at an international conference; and as a guest lecture in the UCLA Freshman class "Methane the other greenhouse problem”, which targets non-STEM students, and the undergraduate/graduate course "Aquatic Geomicrobiology". As methane seeps and relic carbonates are widespread along the continental margins, carbon cycling through seep carbonates is likely a substantial component of the global subseafloor methane budget and its quantification is crucial to estimate long-term burial of methane-derived carbon.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.