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

考恩/约翰逊摘要我们的Lexen计划的主要目标是检验洋壳中存在大量微生物生物圈的假设。这项研究的一个关键组成部分是了解生物圈在不同的地壳地热制度下如何变化，以及如何在地壳年龄和沉积物覆盖范围大不相同的地点显示地下微生物活动的有机碳证据。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温暖流体的旧地壳，(B)沉积的地壳剖面与未沉积的地壳剖面，含氧的地壳流体与缺氧流体，以及(D)长的流体停留时间与短的停留时间。对于关于是否存在次表层生物圈的问题，一个合理的答案需要我们根据其有机成分和微生物分类(脂类和分子遗传探针)来表征来源流体，确定流体运输路径、流体循环深度和停留时间，以便确定我们采样的地壳岩石的面积/体积。最后，重要的是，我们通过比较同一传播中心的老站点和年轻站点的数据，对我们可以在多大程度上推断结果做出一次一阶估计。

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.