Collaborative Research: NSF OCE-BSF: Coupling organic nutrient cycling to methane production in the oligotrophic North Pacific Ocean

合作研究：NSF OCE-BSF：将有机养分循环与贫营养北太平洋甲烷生产耦合

• 批准号: 2241667
• 负责人: Daniel Repeta
• 金额: $ 72.82万
• 依托单位: Woods Hole Oceanographic Institution
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-07-01 至 2026-06-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2241667&HistoricalAwards=false
• 关键词: Collaborative; Research; NSF; OCE; BSF

Open ocean surface waters are natural sources of methane to the atmosphere. As recently as a decade ago the source of this methane was a mystery, because methane production was only known to occur in certain environments without oxygen. Recently, the discovery of several metabolic pathways that enable microbes to transform organic matter into methane in the presence of oxygen has led to a shift away from the idea that methane can only be produced in anaerobic (oxygen-free) environments. The investigators propose that the pathway microbes use to make methane depends on the nutrient conditions that prevail in open ocean surface waters. In the North Atlantic Ocean, phosphorus limits microbial production, and microbes produce methane as a by-product of getting the phosphorus they need from organic compounds that contain phosphorus. In contrast, nitrogen limits microbial production in the North Pacific Ocean. The team proposes that in the North Pacific Ocean microbes produce methane as a by-product of organic nitrogen degradation. To test this hypothesis, they propose to compare the results of geochemical and biological measurements previously made in the North Atlantic with a parallel set of geochemical measurements they propose to make in the North Pacific Ocean. The award will support collaborations between an early career professor at a primarily undergraduate institution (PUI) and a senior scientist, and between US and Israeli scientists. Undergraduate students will participate in interdisciplinary research spanning oceanography, isotope biogeochemistry, and genome science and will conduct research at sea. The microbiology and genomic research will be integrated into course-based undergraduate research experiences at the University of Puget Sound enabling diverse students to participate directly in authentic research. Results will also be integrated into a graduate level course in marine organic geochemistry available on-line through the MIT Open Courseware website. This is a project jointly funded by the National Science Foundation’s Directorate of Geosciences (NSF-GEO) and the Israel Binational Science Foundation (BSF) in accord with the language in the Memorandum of Understanding between the NSF and the BSF. This Agreement allows a single collaborative proposal, involving US and Israeli investigators, to be submitted and peer-reviewed by NSF. Upon successful results of the NSF merit review and recommendation by the cognizant NSF Program of an award, each Agency funds the proportion of the budget and the investigators associated with its own country.The guiding hypothesis of this study is that although surface seawater in the North Atlantic and North Pacific Subtropical Gyres are both sources of methane to the atmosphere, the underlying microbial processes that produce methane in the two basins are fundamentally different. Microbial production in the Sargasso Sea is chronically phosphorus-limited. To mitigate this limitation, some microbes degrade methylphosphonate that is incorporated into the high molecular weight fraction of dissolved organic matter (HMWDOM) into methane and phosphaote. Bacteria expressing the carbon-phosphorus (C-P) lyase enzyme pathway for phosphonate catabolism dominate the Sargasso Sea microbial community and mediate this form of methane production making it the principal route through which excess methane is produced in the Sargasso Sea. In contrast, microbial production in the North Pacific Subtropical Gyre (NPSG) is chronically nitrogen limited and the proposal postulates that nitrogen acquisition through the degradation of methylamines in HMWDOM is a major route through which excess methane is produced. Methylamines are twenty-fold more abundant than methylphosphonate in marine HMWDOM and the aminotransferase gene linked to the conversion of methylamine into methane in freshwater lakes has closely related sequences in marine bacterial genomes. These sequences are abundant and widespread in marine metagenomes. Although the cycling of methylphosphonate and methylamine in oligotrophic surface waters both produce methane, the study postulates that the two processes will yield methane with distinct and characteristic carbon isotopic values. To test this hypothesis, the team will measure the stable carbon isotope value of the methane produced from HMWDOM methylamine and methylphosphonate. The team will also conduct laboratory experiments that test the capacity of diverse oligotrophic and copiotrophic marine bacterial isolates to convert HMWDOM methylamines to methane. This objective is complemented by a field study in the NPSG northwards from Hawaii along 158°W, the longitude of Station ALOHA, to 25-28°N to conduct geochemical and biological measurements associated with each methane production pathway. The team will obtain water column profiles of methane and ethylene concentration (two products of C-P lyase), methane carbon isotopes, and concentrations and carbon isotope values of HMWDOM methylamine and methylphosphonate. The investigators will quantify the rates of methane production from methylamine and methylphosphonate using stable carbon isotope tracers, C-P lyase activity, and the ratio of C-P lyase to aminotransferase gene abundance and expression in the NPSG. Lastly, the team will compare the bioavailability of HMWDOM methylamine and methylphosphonate to natural microbial communities in the NPSG using a metatranscriptomics approach to examine changes in microbial metabolic functions in response to HMWDOM additions. Together, these data will resolve the relative contribution of the methylamine and methylphosphonate pathways to aerobic methane production in the NPSG and the microbial groups and ecosystem properties underlying methane production. Through this interdisciplinary approach, the study will enhance our understanding of processes controlling aerobic methane production in the environment.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.

开放海洋表层水域是大气中甲烷的天然来源，就在十年前，这种甲烷的来源还是一个谜，因为人们知道甲烷的产生只发生在某些没有氧气的环境中。研究人员提出，微生物在有氧的情况下能够将有机物转化为甲烷，这使得人们不再认为甲烷只能在厌氧（无氧）环境中产生。甲烷取决于北大西洋公海表层水域的营养条件，磷限制了微生物的产生，而微生物产生甲烷是从含磷的有机化合物中获取所需磷的副产品。氮限制了北太平洋的微生物生产。研究小组提出，北太平洋的微生物会产生甲烷作为有机氮降解的副产品。为了验证这一假设，他们建议比较地球化学的结果。以及之前在北大西洋进行的生物测量以及他们计划在北太平洋进行的一组平行地球化学测量。该奖项将支持主要本科机构（PUI）的早期职业教授和资深科学家之间的合作，以及美国和以色列科学家之间的合作，本科生将参与海洋学、同位素生物地球化学和基因组科学等跨学科研究，并将在海上进行微生物学和基因组研究，并将其纳入普吉特湾大学的本科生研究经验中。使能研究结果还将被纳入通过麻省理工学院开放课件网站在线提供的海洋有机地球化学研究生课程中，这是由美国国家科学基金会地球科学理事会 (NSF) 共同资助的项目。 -GEO）和以色列两国科学基金会（BSF）根据 NSF 和 BSF 之间的谅解备忘录中的措辞，该协议允许提交并提交一份涉及美国和以色列研究人员的单一合作提案。经 NSF 同行评审。根据 NSF 绩效审查的成功结果以及认可的 NSF 项目的推荐，每个机构资助与其本国相关的预算和研究人员的比例。本研究的指导假设是：尽管北大西洋和北太平洋副热带环流的表层海水都是大气中甲烷的来源，但这两个盆地中产生甲烷的潜在微生物过程却有着根本的不同。为了缓解这种限制，一些微生物将溶解有机物 (HMWDOM) 中的甲基膦酸降解为甲烷和磷酸盐，表达磷酸盐分解代谢的碳磷 (C-P) 裂解酶途径。在马尾藻海微生物群落中占主导地位，并介导这种形式的甲烷生产，使其成为马尾藻海产生过量甲烷的主要途径相比之下，北太平洋副热带环流 (NPSG) 的微生物生产长期受到限制，该提案假设通过 HMWDOM 中甲胺的降解获取氮是产生过量甲烷 20 倍的主要途径。海洋 HMWDOM 中的甲基膦酸含量比甲基膦酸更丰富，而淡水湖中与甲胺转化为甲烷相关的转氨酶基因与海洋细菌基因组中的序列密切相关。这些序列在海洋宏基因组中丰富且广泛存在，尽管寡营养地表水中的甲基膦酸盐和甲胺的循环都会产生甲烷，但该研究假设这两个过程将产生具有独特和特征碳同位素值的甲烷。将测量 HMWDOM 甲胺和甲基膦酸盐产生的甲烷的稳定碳同位素值。该团队还将进行实验室实验，测试各种寡营养和甲基膦酸盐的能力。 NPSG 从夏威夷沿西经 158°（ALOHA 站经度）到北纬 25-28° 的实地研究补充了这一目标，以进行与相关的地球化学和生物测量。该团队将通过水获取甲烷和乙烯浓度（C-P裂解酶的两种产物）、甲烷碳的柱剖面。研究人员将使用稳定碳同位素示踪剂、C-P 裂解酶活性以及 C-P 裂解酶与转氨酶基因丰度的比率来量化甲胺和甲基膦酸的同位素、浓度和碳同位素值。最后，该团队将 HMWDOM 甲胺和甲基膦酸盐与天然的生物利用度进行比较。 NPSG 中的微生物群落使用宏转录组学方法来检查微生物代谢功能因 HMWDOM 添加而发生的变化，这些数据将共同解决甲胺和甲基膦酸途径对 NPSG 以及微生物群体和生态系统中需氧甲烷产生的相对贡献。通过这种跨学科方法，该研究将增强我们对控制环境中需氧甲烷产生的过程的理解。该奖项通过使用基金会的智力价值和更广泛的影响审查标准进行评估，NSF 的法定使命被认为值得支持。