LEXEN: Development of the Capability to Measure Proxies of Microbial Activity within Oceanic Crust (Collaborative Research)

这项研究提出了一项计划，通过检测与这些地下微生物群落相关的特定代谢产物，来检验在水-岩界面以下数百米的离轴脊两侧的海洋上地壳岩石中存在大量微生物生物圈的假设。这些诊断性有机化合物应该伴随着热液流体，这些热液流体已知在上部地壳岩石中循环，并最终在暴露的岩石露头的扩散喷口处排放到上覆的海水中。我们还将检测和系统发育特征（核糖体RNA分子探针）与液体排放相关的任何细胞生物量。为了验证山脊侧翼地下生物圈假说，我们建议建立一个仪器化的“生物毯”，通过相对较小的清除柱（作为代谢（有机碳）产物的陷阱）聚焦从这些弥漫性喷口区域发出的上涌流体。拟议中的仪器覆盖层还将测量热液喷口进入海水时上涌的温度和速度。生物膜的开发将分几个阶段进行：最初的仪器组件测试和流体取样将利用ODP 1026B“软木塞”孔的便捷阀门管道系统，该系统已记录了65 C流出流体；后续的完整原型仪器将部署在山脊侧露头（Cascadia盆地Baby Bare）和大洋中山脊扩展中心（Endeavour段）的活跃扩散喷口上，这些地方的通量率很高，流体的任何成分的信噪比都相当大。直接探测到一个广泛分布的生物群落，生活在古老的山脊侧翼区域的海底下，将极大地改变我们对生物生产力和全球碳预算的估计，并对我们对地球的哲学观点产生深远的影响。＊＊＊

9729671 Johnson This research suggests a program to test the hypothesis that there is a substantial microbial biosphere living within the oceanic upper crustal rocks of the off-axis ridge flanks, hundreds of meters below the water-rock interface, by detecting specific metabolic products which are associated with these sub-surface microbial communities. These diagnostic organic compounds should accompany the hydrothermal fluid that is known to circulate within the upper crustal rocks and eventually discharges into the overlying seawater at diffuse vent sites in exposed rock outcrops. We will also detect and phylogeneticallv characterize (ribosomal RNA molecular probe) any cellular biomass associated with fluid discharges. To test the ridge flank subsurface biosphere hypothesis, we propose to build an instrumented "bio-blanket" that focuses up-welling fluid emanating from these diffuse vent areas through relatively small scavenging columns that serve as traps for metabolic (organic carbon) products. The proposed instrumented blanket would also measure up-welling temperatures and velocities as the hydrothermal fluid vents into seawater. The development of the bio-blanket will be in several stages: initial instrument-component tests and fluid sampling will exploit the convenient valved- plumbing system of the "corked" ODP Hole 1026B, which has documented 65 C outflowing fluids; subsequent complete prototype instruments will be deployed over active diffuse vents at both an exposed outcrop at a ridge flank site (Baby Bare, Cascadia Basin) and a mid-ocean ridge spreading center (Endeavour Segment), where flux rates are high and the signal-to-noise ratio of any component of the fluid is quite large. The direct detection of a wide-spread biological community, living within the sub-surface ocean floor in the older ridge flank regions, would dramatically alter our estimates of biological productivity and the global carbon budgets, and have a profound impact on our philosophical view of the earth. ***