Hydrothermal and microbial controls on organic carbon mobilization from Guaymas Basin sediments

热液和微生物对瓜伊马斯盆地沉积物有机碳动员的控制

• 批准号: 2023656
• 负责人: Sunita Shah Walter
• 金额: $ 53.84万
• 依托单位: University of Delaware
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-09-01 至 2024-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2023656&HistoricalAwards=false
• 关键词: Hydrothermal; microbial; controls; organic; carbon

Organic carbon stored in marine sediments and sedimentary rocks are a critical component of the global carbon cycle. Buried organic carbon balances atmospheric CO2 concentrations over long timescales and is linked to the regulation of Earth’s climate. Microbial activity is a key driver of processes that break down and release carbon from sediments. This project investigates organic carbon in marine sediments and examines its bioavailability to microbes. The setting for the project is the Guaymas Basin of the Gulf of California which receives organic matter inputs from land during seasonal rains and from marine phytoplankton at the sea surface. Guaymas Basin is also a site of active seafloor spreading and hydrothermal heating (i.e., the transfer of heat from magma to sediments and ocean water), which will allow the effects of heating on the bioavailable portion of organic carbon to be investigated. Results from this project will improve our understanding of how microbes reintroduce this buried organic carbon back into the “active” carbon cycle, as well as how this microbial activity is influenced by hydrothermal heating and organic carbon composition. The project also incorporates an international collaboration and an educational cross-border exchange of students between the US and Canada. Results will be shared broadly through videos produced by the Delaware Sea Grant and a content created by the Canadian podcast, Broad Science.Using the gradients available in the context of Guaymas Basin sediments, we will investigate the effects of hydrothermal heating, burial depth (physical factors), sedimentary organic carbon composition and oxygen availability (geochemical factors) and microbial community (biological factors) on the bioavailability and mobilization/utilization of sedimentary organic carbon. Guaymas Basin features several advantages that make it uniquely suited for our proposed studies including the fact that 150 meters of sediment thickness are within the analytical window of radiocarbon dating which will allow us to take advantage of 14C (radiocarbon) as a natural tracer of marine carbon sources. Large gradients of temperature and geochemistry are also created by widespread emplacement of magmatic sills at varied depths in the sediment column. Such hydrothermal heating transforms sedimentary organic carbon in some locations from freshly synthesized photosynthetic biomass to petroleum hydrocarbons on a compressed, 14C-friendly timescale. Analyses will include: (1) carbon isotopic analysis of biomarkers representative of marine-derived, terrestrial and hydrothermal organic carbon reservoirs within sediments, (2) carbon isotopic measurements on biomolecules representative of natural microbial populations, (3) aerobic bioreactor incubations of sediments with their natural microbial population and analysis of the isotopic composition of CO2 released by respiration, and (4) aerobic bioreactor incubations of sediments that have been pre-heated to promote organic carbon transformations and isotopic analysis of CO2 respired by a bacterial isolate. Our results will provide an exceptionally detailed view of the dependence of organic carbon bioavailability on burial depth, heating history, in situ temperature, oxygen availability, organic carbon composition, and microbial functional capabilities that, to our knowledge, will be unprecedented.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.

储存在海洋沉积物和沉积岩中的有机碳是全球碳循环的重要组成部分。埋藏的有机碳在长时间尺度上平衡了大气中的二氧化碳浓度，并与地球气候的调节有关。微生物活动是沉积物分解和释放碳过程的关键驱动因素。本项目研究海洋沉积物中的有机碳，并研究其对微生物的生物可利用性。该项目位于加利福尼亚湾的瓜伊马斯盆地，在季节性降雨期间从陆地和海面的海洋浮游植物中吸收有机物。瓜伊马斯盆地也是海底扩张和热液加热（即从岩浆到沉积物和海水的热量转移）活跃的地点，这将允许研究加热对有机碳的生物可利用部分的影响。该项目的结果将提高我们对微生物如何将这些埋藏的有机碳重新引入“活性”碳循环的理解，以及这种微生物活动如何受到热液加热和有机碳组成的影响。该项目还包括美国和加拿大之间的国际合作和教育跨境学生交流。研究结果将通过特拉华海洋基金制作的视频和加拿大播客“广泛科学”创建的内容广泛分享。利用瓜伊马斯盆地沉积物中可利用的梯度，研究热液加热、埋藏深度（物理因素）、沉积有机碳组成和氧有效性（地球化学因素）以及微生物群落（生物因素）对沉积有机碳生物有效性和动员利用的影响。Guaymas盆地有几个优势，使其特别适合我们提出的研究，包括150米的沉积物厚度在放射性碳测年的分析窗口内，这将使我们能够利用14C（放射性碳）作为海洋碳源的天然示踪剂。在沉积物柱的不同深度，岩浆断层的广泛就位也造成了温度和地球化学的巨大梯度。这样的热液加热将一些地方的沉积有机碳从新合成的光合生物质转化为石油碳氢化合物，时间尺度被压缩，对14c友好。分析将包括：(1)沉积物中具有代表性的海源、陆源和热液有机碳储层生物标志物的碳同位素分析；(2)具有代表性的天然微生物群体的生物分子的碳同位素测量；(3)沉积物及其天然微生物群体的好氧生物反应器培养及呼吸释放CO2的同位素组成分析。(4)沉淀物的好氧生物反应器培养，沉淀物经过预热以促进有机碳转化，并对细菌分离物呼吸的二氧化碳进行同位素分析。我们的研究结果将为有机碳生物利用度对埋藏深度、加热历史、原位温度、氧气可用性、有机碳组成和微生物功能能力的依赖提供一个非常详细的视图，据我们所知，这将是前所未有的。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。