Cycling of Labile Intermediates at the Oxic/Anoxic Interface

每年海洋沉积物中90%以上的有机碳是在沉积物-水界面几厘米内的缺氧沉积物中发现的。此外，据估计，在缺氧条件下再矿化的有机碳量约为氧气环境下再矿化量的10%至100%，厌氧分解在决定最终被掩埋的物质的数量和化学成分方面起着重要作用。然而，缺氧条件对特定有机化合物分解速率的影响尚不清楚。我们可以研究周转率常数变化和生产速率变化对有机化合物浓度的相对重要性的一个环境是氧/缺氧过渡区。氧/缺氧界面是一个微生物种群分层的区域，并且具有快速变化的特性。这项研究将是第一个关注影响发酵中间体（氢、醋酸、丙酸、低分子量胺）和DOC在缺氧/缺氧界面附近分布和周转的过程的研究之一，从而将为这些系统中水柱碳再生的位置提供有价值的信息。结果还将提供关于不稳定化合物的周转率如何在氧化还原梯度内变化的见解，以及周转率或生产速率的变化是否对浓度最大值负责。当与微生物学数据进行比较时，结果还将提供关于不同微生物种群在碳周转中所起作用的定性信息。

More than 90% of the organic carbon buried in marine sediments each year is found in sediments which are anoxic within a few centimeters of the sediment-water interface. In addition, the amount of organic carbon which is remineralized under anoxic conditions has been estimated to be between about 10% and almost 100% of the amount remineralized in oxic environments and anaerobic decomposition plays an important role in determining the quantity and chemical composition of the material which is ultimately buried. However, the effect of anoxic conditions on the decomposition rate of specific organic compounds is poorly understood. One environment in which we can study the relative importance of changes in turnover rate constant and changes in production rate to concentrations of organic compounds is the oxic/anoxic transition zone. The oxic/anoxic interface is a region of stratified microbiological populations, and of rapidly changing properties. This study will be one of the first to focus on the processes affecting the distribution and turnover of fermentation intermediates (hydrogen, acetate, propionate, low molecular weight amines) and of DOC near the oxic/anoxic interface, and will thus provide valuable information on sites of water column carbon regeneration in such systems. The results also will provide insights on how turnover rates of labile compounds vary within redox gradients, and whether variations in the turnover rates or in production rates are responsible for concentration maxima. When compared with microbiological data, the results will also provide qualitative information about the roles played by the different microbial populations in carbon turnover.