Collaborative Research: Redefining the footprint of deep ocean methane seepage for benthic ecosystems

这项研究探讨了深海生物在决定太平洋大陆边缘甲烷这一潜在温室气体的命运和足迹方面的作用。研究人员正在评估深海甲烷层，该甲烷层由消耗甲烷的微生物群落和直接以消耗甲烷的微生物为食或与之形成共生关系的动物定义。他们还在调查从甲烷中间接获得能量的动物群落，以及那些利用碳酸盐岩的动物群落，碳酸盐岩是海底沉积物中甲烷消耗的物理表现。对阿拉斯加（4400-5500米）和南加州（450-1040米）深水沃茨中甲烷渗漏的研究，使人们能够比较不同食物限制和氧气制度下的甲烷层。通过应用不同的化学，同位素，显微镜和基于遗传的分析渗漏微生物和动物，这项研究正在推进甲烷对深海生物多样性和生态系统功能的贡献的理解，这些信息可以为美国沃茨的管理和保护行动提供信息。除了在他们的家乡机构为研究生和本科生提供培训外，研究人员还与阿拉斯加土著科学和工程项目（ANSEP）合作。他们正在招募阿拉斯加本科生参与研究，为ANSEP的在线资源做出贡献，促进科学家与初中和高中学生之间的互动，并参加ANSEP的年度住宅海洋科学职业探索计划，让中学生学习深海生态系统和海洋相关领域的各种职业途径。 微生物产生和消耗甲烷是动态的，在沿着大陆边缘广泛存在，深海甲烷渗漏区的一些动物依靠甲烷的氧化和封存获得营养。与此同时，对深海环境中依赖甲烷的过程和共生现象的了解仍然是初步的。本研究的目的是：1）研究甲烷共生体中动物的多样性和甲烷氧化微生物的异养消耗，以及这些共生体如何扩展渗漏的外围，促成非渗漏的大陆坡食物网;和2）确定渗漏外围的碳酸盐是否维持活性甲烷氧化微生物组合，通过甲烷的厌氧氧化或动物消耗的自由生活的硫化物氧化细菌，为硫营养共生体提供局部食物来源或化学燃料。研究人员正在通过对阿留申边缘的一个深渗漏点和南加州附近的一个浅渗漏点进行调查、取样和表征微生物、水、沉积物、碳酸盐和动物来实现这些目标。船上实验和实验室分析正在使用分子，同位素，地球化学和放射性示踪剂工具，以了解在多个氧气水平，压力和光合食物输入下甲烷源碳从好氧甲烷氧化菌的转移。这种方法提供了一个广泛的透镜，通过它来检查甲烷渗漏足迹，允许重新解释过去的观察，并确定新的科学领域，为未来的研究。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进行评估，被认为值得支持。

This research examines the role of deep-sea organisms in determining the fate and footprint of methane, a potent greenhouse gas, on Pacific continental margins. The investigators are evaluating the deep ocean methanosphere defined by the microbial communities that consume methane and the animals that directly feed on or form symbioses with methane-consuming microbes. They are also investigating animal communities that gain energy indirectly from methane, as well as those that take advantage of carbonate rocks, the physical manifestation of methane consumption in seafloor sediments. The study of methane seeps in the deep waters of both Alaska (4400-5500 meters) and Southern California (450-1040 meters) is enabling comparisons of the methanosphere under different food-limitation and oxygen regimes. By applying diverse chemical, isotopic, microscopy, and genetic-based analyses to seep microbes and fauna, this study is advancing understanding of the contribution of methane to deep-sea biodiversity and ecosystem function, information that can inform management and conservation actions in US waters. In addition to training for graduate and undergraduate students at their home institutions, the investigators are collaborating with the Alaska Native Science and Engineering Program (ANSEP). They are recruiting Alaskan undergraduates to participate in the research, contributing to ANSEP’s online resources that promote interaction between scientists and middle and high school students, and participating in ANSEP’s annual residential Career Exploration in Marine Science programs to engage middle school students in learning about deep-sea ecosystems and the variety of career pathways available in marine related fields. Microbial production and consumption of methane is dynamic and widespread along continental margins, and some animals within deep-sea methane seeps rely on the oxidation and sequestration of methane for nutrition. At the same time, understanding of methane-dependent processes and symbioses in the deep-sea environment is still rudimentary. The goals of this study are to 1) examine the diversity of animals involved in methane-based symbioses and heterotrophic consumption of methane-oxidizing microbes and how these symbioses extend the periphery of seeps, contributing to non-seep, continental slope food webs; and 2) determine whether carbonates on the seep periphery sustain active methanotrophic microbial assemblages, providing a localized food source or chemical fuel for thiotrophic symbioses, via anaerobic oxidation of methane, or free-living, sulfide-oxidizing bacteria consumed by animals. The investigators are addressing these goals by surveying, sampling, and characterizing microbes, water, sediments, carbonates and animals at a deep seep site on the Aleutian Margin and a shallow site off Southern California. Shipboard experiments and laboratory analyses are using molecular, isotopic, geochemical, and radiotracer tools to understand transfer of methane-sourced carbon from aerobic methanotrophs under multiple oxygen levels, pressures, and photosynthetic food inputs. This approach offers a wide lens by which to examine the methane seep footprint, allow reinterpretation of past observations, and identify new scientific areas for future study. Improved characterization of the deep continental margin methanosphere informs climate science, biodiversity conservation, and resource management.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.