Collaborative Proposal: Site Survey and Initial Characterization of North Pond: Microbiology, Biogeochemistry, Seismic Profiles

微生物细胞存在于世界各地海洋的浅层和深层沉积物中。这些细胞构成了地球原核生物生物量的主要部分，它们的活性催化了埋藏有机物的分解。同样，微生物在海洋地壳中定居，导致年轻的脊侧玄武岩的氧化蚀变。尽管它们在世界各地都很丰富，但这些生物的多样性、栖息地和传播途径却没有得到明确的定义。人们对它们的功能基因和代谢活动知之甚少，这些代谢活动使这些原核生物能够在年轻的地壳环境中生长和生存。北塘是大西洋中脊西侧22°45′n和46°05′w上一个孤立的东北向沉积物塘；它被年轻的（7 Ma），多孔的洋中脊玄武岩包围和下面，它与大西洋深海盆地和外脊侧翼的沉积物覆盖分离。这种环境为研究地下微生物群落的扩散途径、发生和定植模式提供了一个“天然实验室”。特别是研究可以从深海水柱、深层地下沉积物和山脊侧玄武岩中区分细菌和古细菌。目前深层地下微生物学关注的问题是“那里有什么样的微生物生命，为什么？”，而避免了必要的补充“它是如何到达那里的？”这项研究将实现这一目标，并设想在北池建立一个微生物观测站，作为未来IODP活动的一部分。通过追踪北池沉积物的物理和化学“特征”，研究将限制流体运输途径和流速，这些将与特定地点的微生物组成、关键代谢基因库和地下微生物群落的生物地球化学活性相关。本研究通过将热流、地震信息和孔隙流体化学数据与沉积物微生物采样相结合，对北池沉积物-基底界面进行了详细的制图。目标有两个：1)对北池进行全面的现场调查，包括为我们即将到来的IODP北池巡航做准备的水文约束；2)结合生物地球化学特征和沉积物环境的流动路径，对近地表微生物群落进行调查。这次现场调查巡航将允许必要的改进船上和岸上的方法和样品处理，以准备我们的IODP巡航。更广泛的影响。海洋地下生物群落的生物地球化学活动、组成和时空动态是海洋科学和地球微生物学研究的一个新兴中心课题。研究人员计划通过整合课程材料和REU学生的直接参与，将研究结果直接整合到他们机构正在进行的本科生和研究生教育中。研究人员将通过JOI杰出演讲者系列吸引更广泛的公众。最后，这次现场调查是将北池发展成为地下微生物学国际协调基准研究（即微生物观测站）的更大愿景的一部分。

Microbial cells occur in shallow and deep sediments throughout the world's oceans. These cells constitute a major portion of the Earth's prokaryotic biomass and their activity catalyzes the decomposition of buried organic matter. Similarly, microorganisms colonize the ocean crust, leading to the oxidative alteration of young ridge flank basalts. Despite their cosmopolitan abundance, the diversity, habitat, and dispersal pathways of these organisms are poorly defined. Little is known regarding their functional genes and the metabolic activities that allow these prokaryotes to grow and survive in the young crustal environment. North Pond is an isolated northeast-trending sediment pond on the western flank of the Mid-Atlantic Ridge (MAR) at 22deg45'N and 46deg05'W; it is surrounded and underlain by young (7 Ma), porous mid-ocean ridge basalt, and it is isolated from the sediment cover of the Atlantic abyssal basins and outer ridge flanks. This setting provides a "natural laboratory" for examining subsurface microbial community dispersal pathways, occurrence, and colonization patterns. In particular studies can differentiate bacteria and archaea from the deep-sea water column, deep subsurface sediments, and ridge flank basalt. Current deep subsurface microbiology focuses on the question "What kind of microbial life is there, and why?" while avoiding its necessary complement "How did it get there?" This study will accomplish that goal with a vision toward establishing a microbial observatory at North Pond as part of future IODP campaigns. By tracing physical and chemical "signatures" in North Pond sediments, the research will constrain fluid transport pathways and flow rates, and these will be correlated to site-specific microbial composition, key metabolic gene repertoire, and biogeochemical activity of subsurface microbial communities. This research focuses on detailed mapping of the sediment-basement interface of North Pond, by coupling heat flow, seismic information, and pore fluid chemistry data to microbial sampling of the sediments. The goals are two-fold: 1) to conduct a comprehensive site survey of North Pond that includes constraining the hydrology in preparation for our upcoming IODP cruise to North Pond, and 2) to perform a survey of near-surface microbial communities in conjunction with the biogeochemical characteristics and flow paths of their sediment environment. This site survey cruise will permit necessary refinement in shipboard and shore-based methodology and sample handling in preparation of our IODP cruise. Broader Impacts. The biogeochemical activities, composition and temporal and spatial dynamics of marine subsurface communities are an emerging central topic in marine sciences and geomicrobiology. The researchers plan to integrate the findings directly into ongoing undergraduate and graduate student education at their institutions through integration of materials in coursework, and the direct involvement of an REU student. The researchers will engage the broader public via the JOI distinguished Speaker series. Finally, this site survey is part of a much larger vision to develop North Pond into an internationally coordinated benchmark study in subsurface microbiology (i.e., a microbial observatory).