A SGER Proposal to Test the Hypothesis of a Sub-Surface Biosphere within Oceanic Crust

我们的LEXEN项目的主要目标是验证在海洋地壳中存在大量微生物生物圈的假设。本研究的一个关键组成部分是了解在不同地壳-地热制度下生物圈如何变化，以及地下微生物活动的有机碳证据如何在不同地壳年龄和沉积物覆盖的地点表现出来。我们将确定控制地壳内生命分布的过程，特别是(a)具有高温流体的年轻地壳与具有热流体的老地壳，(b)沉积与非沉积地壳部分，含氧地壳流体与缺氧流体，以及(d)流体停留时间长与停留时间短。对于地下生物圈是否存在的问题，一个合理的答案要求我们根据其有机组成和微生物分类（脂质和分子遗传探针）来描述源流体的特征，确定流体的传输路径、流体循环的深度和停留时间，以便确定我们正在取样的地壳岩石的面积/体积。最后，重要的是，我们要通过比较来自同一传播中心的老站点和新站点的数据，对我们如何在全球范围内推断我们的结果进行一阶估计。

Cowen/Johnson AbstractThe primary goal for our LEXEN program is to test the hypothesis that there is a substantial microbial biosphere within oceanic crust. A critical component of this study is to learn how this biosphere varies under different crustal-geothermal regimes, and how the organic carbon evidence of the sub-surface microbial activity is manifested at sites of widely different crustal age and sediment cover. We will be determining the processes that control the distribution of life within the crust, specifically within (a) young crust with high temperature fluids vs old crust with warm fluids, (b) sedimented vs un-sedimented crustal sections, oxygenated crustal fluids vs anoxic fluids, and (d) long fluid residence times vs short residence times. A plausible answer to the question regarding the existence of a sub-surface biosphere requires that we characterize the source fluids in terms of their organic composition and microbial taxonomy (lipids and molecular genetic probes), identify the fluid transit paths, the depth of fluid circulation and residence times in order to determine the area/volume of the crustal rocks that we are sampling. Finally, it is important that we make a first-order estimate of how globally we can extrapolate our results, by comparison of data from both old and young sites at the same spreading center.