Molecular-isotopic studies of subsurface carbon turnover in hydrate-bearing sediments at the Cascadia Margin (IODP Expedition 311)

我们建议在卡斯卡迪亚边缘的水合物含海洋沉积物中研究与甲烷的生产和积累有关的地球化学过程。在ODP/IODP针对的绝大多数水合物区，特别是产甲烷区，溶解无机碳和有机碳的浓度异常高，这表明一些约束机制不佳，相对于其他类似沉积环境中的非水合物系统，在含水合物的地下环境中提高了有机碳的周转率。该项目的目标是更好地了解生物介导的碳转化，这些碳转化有助于在含水合物的沉积系统中在地质时间跨度内积累甲烷。我们将把我们的注意力集中在溶解的有机碳池，特别是我们将研究挥发性脂肪酸的化合物特异性同位素组成，由完整的膜脂，代表活的地下原核生物的化合物特异性同位素信息的补充。总之，这些技术可以提供深入了解地下原核生物的碳周转和碳代谢的机制。这些新技术已经在我们的实验室中得到了很大程度的改进，并在其他地下环境中得到了成功的测试。该提案旨在为涉及博士后研究员和IODP Expedition 311船上科学家Verena Heuer博士的博士后研究提供资金。

We propose to study the biogeochemical processes associated with the production and accumulation of methane in hydrate-bearing marine sediments at the Cascadia Margin. Anomalously high concentrations of dissolved inorganic and organic carbon in the large majority of hydrate provinces targeted by ODP/IODP, in particular in methanogenic zones, suggest that some poorly constrained mechanism( s) enhance turnover of organic carbon in hydrate-bearing subsurface environments relative to nonhydrate systems in otherwise similar depositional settings. The project goal is to gain a better understanding of the biologically mediated carbon transformations that contribute to accumulation of methane in geologic time spans in hydrate-bearing sedimentary systems. We will focus our attention on the pool of dissolved organic carbon; in particular we will study the compound-specific isotopic compositions of volatile fatty acids, complemented by compound specific isotope information of intact membrane lipids that represent live subsurface prokaryotes. Together, these techniques can provide insights into mechanisms of carbon turnover and carbon metabolism of subsurface prokaryotes. These new techniques have been largely advanced in our laboratory and successfully tested in other subsurface environments. The proposal seeks funding for postcruise research involving postdoctoral investigator and IODP Expedition 311 shipboard scientist Dr. Verena Heuer.