Collaborative Research: Hydrogen Isotope Biogeochemistry of Anoxic Environments - Field and Laboratory Studies

摘要本项目正在开发化合物特异性氢同位素分析，作为缺氧环境过程导向生物地球化学研究的工具。由于硫酸盐还原菌在海洋环境中对碳循环的定量重要性，研究的重点是硫酸盐还原菌。对黑海和阿拉伯海沉积物捕集器中脂肪酸的初步测量表明，dD值低至-350。该项目正在测试一种假设，即厌氧原核生物对分子氢（H2）的消耗导致脂质中氘(D)的强烈消耗，因为H2本身相对于水是同位素耗尽的（通常为-600或更多）。实地研究的重点是从黑海和圣莫尼卡盆地收集的悬浮颗粒物和沉积物中提取的生物标志物脂质中的dD。这项工作的结果将是对缺氧环境中特定化合物dD值的第一次实质性调查，并应提供对大同位素分馏负责的生物群的指示。实验室实验的重点是脂质氢的来源（即H2与水）和通过操纵SRB培养的氢同位素分馏。研究了代谢率、H2浓度、种类和底物的影响。

Valentine/Sessions AbstractThis project is developing compound-specific hydrogen isotope analyses as a tool for process-oriented biogeochemical studies of anoxic environments. Research is focusing on sulfate-reducing bacteria (SRB) due to their quantitative importance for carbon cycling in marine settings. Preliminary measurements of fatty acids from sediment traps in the Black and Arabian Seas indicate dD values as low as -350. This project is testing the hypothesis that consumption of molecular hydrogen (H2) by anaerobic prokaryotes leads to lipids strongly depleted in deuterium (D), because H2 itself is isotopically depleted (typically -600 or more) relative to water. Field studies is focusing on dD in biomarker lipids extracted from suspended particulate matter and sediments collected in the Black Sea and Santa Monica Basin. The results of this work will represent the first substantial survey of compound-specific dD values in anoxic environments, and should provide an indication of the biota responsible for the large isotopic fractionations. Laboratory experiments are focusing on the sources of lipid hydrogen (i.e., H2 versus water) and hydrogen-isotopic fractionations through manipulation of SRB cultures. Effects of metabolic rate, H2 concentration, species, and substrate are being examined.