Collaborative Research: Structure, Function and Evolution of Authigenic, Methane-Derived Carbonate Ecosystems

与甲烷渗漏相关的自生碳酸盐沉淀通常由甲烷厌氧氧化（AOM）介导。这种微生物过程产生了大量的碳酸盐岩，为大陆边缘引入了栖息地的异质性，并为海底释放的甲烷衍生碳提供了一个主要的储存库。本研究将通过在演替背景下描述相关的微生物、有孔虫、大型动物和巨型动物群落，调查这些碳酸盐基质在渗漏环境中形成独特生态系统的程度。将在哥斯达黎加边缘（730-1300米）和俄勒冈边缘（590米）的水合物山脊北部的4个深海地点进行碳酸盐岩的调查和采样。位置差异和相关的水深、氧合、渗漏巨型动物和碳酸盐地层变化预计会影响群落组成。本研究将对活跃、弱和无甲烷渗流的碳酸盐岩栖息组合进行表征，并进行岩石定植和移植实验，以验证以下主要假设：(1)在海底-水界面活跃渗流条件下，自生碳酸盐岩作为一个独特的生态系统，在AOM的推动下发挥作用，具有自己的（化学合成）初级和次级生产来源；(2)在甲烷供应和微生物活动的驱动下，渗碳酸盐区系发生演替；(3)无底渗碳酸盐组合主要包括微生物、原生动物和后生动物，它们在分类和进化上与周围渗沉积物的生物群不同，但在生态和进化上与深海、硬底和还原性动物（包括渗、喷口、珊瑚丘和鲸骨）相关。将对单个岩石进行分裂和切片，用于碳酸盐矿物学和同位素分析，对内源性微生物及其各自的δ 13C特征进行FISH-SIMS分析，对动物（原生动物和后生动物）进行分类，生活方式和位置研究。有孔虫和后生动物原生质的稳定同位素和脂质分析、有孔虫测试和软体动物壳的δ 18O和δ 13C特征将与微生物和碳酸盐特征联系起来，以评估营养途径和甲烷释放的古代用物。古细菌和AOM被假设为两者的关键。退化的碳酸盐基质将在活跃和不活跃的地点放置一年，以研究早期动物演替和外部渗流的作用。在不活动和活动地点之间移植岩石，并进行适当的操作控制，将提供有关动物对渗流的依赖以及在没有渗流的情况下AOM的持久性的额外信息。将与渗漏沉积物、其他生物基质（贻贝、蛤蜊、管虫）以及其他深海还原性和硬地系统（喷口、鲸鱼、深水珊瑚）进行群落比较。大型动物组合将是DNA，选择环节动物和有孔虫类群将作为系统发育分析的目标，以评估与其他硬地还原生态系统（喷口）动物的进化亲缘性。更广泛的影响：本研究对社会的好处包括：(1)了解渗透碳酸盐生态系统，以改善海洋资源管理，更全面地评估海底生物多样性、碳循环和对极端环境的适应；(2)建立碳酸盐生态系统演替变化模型，并利用其动物作为代用物，更准确地评估过去的甲烷释放和古气候变化。教育和外联将包括当地学校的介绍；通过SURF、STARS和REU项目招募的未被充分代表的群体（女性；来自农村社区的第一代大学生），在本科、研究生和博士后阶段对未来科学家进行跨学科的、实际操作的海上培训。研究成果将纳入深海生物学、微生物学、地质学、古生物学、海洋学和底栖生态学课程的讲座、练习和实地考察，并纳入海洋生物普查和SIO底栖无脊椎动物收集所管理的网站和数据库。

Authigenic carbonate precipitation associated with methane seepage is typically mediated by anaerobic oxidation of methane (AOM). This microbial process produces massive amounts of carbonate rock, introducing habitat heterogeneity to continental margins and providing a major repository for methane-derived carbon released from the sea floor. This study will investigate the extent to which these carbonate substrates form a distinct ecosystem within the seep environment by characterizing associated microbial, foraminiferal, macrofaunal and megafaunal communities in a successional context. Surveys and sampling of carbonate will take place at 4 bathyal locations on the Costa Rica margin (730-1300 m) and at Hydrate Ridge North on the Oregon margin (590 m). Location differences and associated water depth, oxygenation, seep megafauna and carbonate formation variation are expected to influence community composition. This study will characterize assemblages inhabiting carbonates subject to active, weak and no methane seepage, and conduct rock colonization and transplant experiments to address the following main hypotheses:(1) Under conditions of active seepage at the seafloor-water interface, authigenic carbonate functions as a distinct ecosystem fueled by AOM, with its own sources of (chemosynthetic) primary and secondary production; (2) Seep carbonate faunal communities undergo succession driven by methane supply and microbial activity; (3) Sessile seep carbonate assemblages include mainly microbial, protozoan and metazoan species that are taxonomically and evolutionarily distinct from the biota of surrounding seep sediments, but ecologically and evolutionarily related to deep-sea, hard-substrate and reducing faunas, including those from seeps, vents, coral mounds and whale bones. Single rocks will be split and sectioned for carbonate mineralogy and isotopic analysis, FISH-SIMS analyses of endogeneous microorganisms and their respective delta 13C signatures, faunal (protozoan and metazoan) taxonomic, lifestyle and position studies. Stable isotopic and lipid analyses of foraminifera and metazoan protoplasm, delta 18O and delta 13C signatures of foraminiferan tests and mollusk shells will be linked to microbial and carbonate signatures to assess trophic pathways and paleo proxies for methane release. Archaea and AOM are hypothesized as key to both. Defaunated carbonate substrates will be deployed at active and inactive sites for 1 year to examine early faunal succession and the role of external seepage. Rocks transplanted between inactive and active sites, with appropriate manipulation controls, will provide additional information about faunal reliance on seepage and persistence of AOM in the absence of seepage. Community comparisons will be drawn with seep sediments, other biotic substrates (mussels, clams, tubeworms) and with other deep-sea reducing and hardground systems (vents, whales, deep-water corals). Macrofaunal assemblages will be DNA and selected annelid and foraminiferan taxa will be targeted for phylogenetic analyses to assess evolutionary affinities with fauna from other hardground-reducing ecosystems (vents).Broader Impacts: Benefits of this research to society include: (1) an understanding of seep carbonate ecosystems for improved marine resource management and more comprehensive assessments of seafloor biodiversity, carbon cycling, and adaptations to extreme environments; and (2) a model for successional changes in carbonate ecosystems and the use of their faunas as proxies to more accurately assess past methane release and paleoclimate change. Education and outreach will include local school presentations; web site development and interdisciplinary, hands-on, at-sea training of future scientists at undergraduate, graduate, and post-doc levels, including under-represented groups (women; first-generation university students from rural communities) recruited through SURF, STARS and REU programs. Research results will be incorporated into lectures, exercises and field trips for deep-sea biology, microbiology, geology, paleontology, oceanography and benthic ecology courses, and onto websites and databases managed by the Census of Marine Life and the SIO Benthic Invertebrate Collection.