Influence of Pre- and Post-depositional Processes on Sedimentary Organic Matter Composition

海洋沉积物中有机碳（OC）的封存是全球碳循环的关键组成部分，然而，关于埋藏在大陆边缘和深海中的有机物质的确切来源和性质，仍有许多未解之谜。越来越多的证据表明，海洋颗粒OC受到海底洋流的广泛重新分配，这一过程可能在大陆边缘特别普遍。如果平流过程广泛存在，这一发现将对我们对全球碳循环的理解和对古海洋记录的解释产生重要影响。在这个项目中，伍兹霍尔海洋研究所的研究人员将继续对当代海洋沉积物中保存的有机物质进行分子多同位素（特别是14C）研究。拟议的研究建立在他们先前工作的几个关键和有些意想不到的发现的基础上，这些发现提出了新的问题，并挑战了海洋环境中有机物来源和循环的当前范式。这些发现表明，横向颗粒运输对大陆边缘沉积物中埋藏的有机质的数量和类型具有普遍影响，总体上表明，沉积前过程在决定海洋中陆地和海洋有机碳的命运方面起着重要作用。研究小组试图确定他们的初步发现是否适用于广泛的沉积环境，并更好地描述和量化潜在的机制。特别是，他们希望量化OC在大陆边缘横向运输中的时间尺度，研究底栖网状层在促进沉积物再分配和有机质保存方面的作用，并在分子水平上了解沉积有机质的年龄-反应性关系。就更广泛的影响而言，我们有理由期待这项研究的发现将对检验海洋边缘在封存大气二氧化碳中的作用和预测对气候变化的反应的模型产生影响。除了对大气中二氧化碳浓度增加的后果进行评估外，这项研究的结果还可能改善目前对引入海洋边缘的其他人为污染物的扩散和命运的认识。PI积极为博士后、研究生和本科生提供建议。拟议的研究计划将成为一个由博士后研究员领导的项目的基础。PI也经常让本科生暑期学生参与他的研究，预计这项活动将在当前项目中继续进行。这项研究的结果也将被纳入麻省理工学院-世界卫生组织海洋学联合项目的课程。

OCE-0526268The sequestration of organic carbon (OC) in marine sediments is a key component of the global carbon cycle, yet there are still many unanswered questions regarding the exact origin and nature of the organic matter that is buried on the continental margins and in the deep sea. A growing body of evidence indicates that oceanic particulate OC is subject to extensive redistribution by bottom currents, a process that may be particularly prevalent on continental margins. If advective processes are widespread, this finding would have important implications for our understanding of the global carbon cycle and for the interpretation of the paleoceanographic record. In this project, researchers at the Woods Hole Oceanographic Institution will continue their molecular multi-isotopic (especially 14C) investigations of organic matter preserved in contemporary marine sediments. The proposed research builds on several key and somewhat unexpected findings from their prior work that raise new questions and challenge current paradigms on sources and cycling of organic matter in the marine environment. These findings implicate lateral particle transport as a pervasive influence on the amount and type of organic matter that is buried in continental margin sediments, and in general, suggest that pre-depositional processes play an important role in dictating the fate of terrestrial and marine organic carbon in the oceans.The research team seeks to determine whether their preliminary findings are applicable to a broad range of depositional settings and to better characterize and quantify the underlying mechanisms. In particular, they expect to quantify timescales involved in the lateral transport of OC across continental margins, examine the role of benthic nepheloid layers in promoting sediment redistribution and organic matter preservation, and develop a molecular-level understanding of age-reactivity relationships in sedimentary organic matter. In terms of broader impacts, there is reason to expect that findings from this study will bear on models that examine the role of the ocean margins in the sequestration of atmospheric CO2 and forecast the response to climate change. In addition to assessment of the consequences of increasing atmospheric CO2 concentrations, the results of the study may improve current knowledge of the dispersion and fate of other anthropogenic contaminants introduced to the oceans margins. The PI is active in advising postdoctoral, graduate, and undergraduate summer students. The proposed research program will form the foundation for a project to be led by a postdoctoral investigator. The PI also routinely involves undergraduate summer students in his research, and it is anticipated that this activity will continue with respect to the current project. Findings from this study will also be incorporated into the curriculum of the MIT-WHOI Joint Program in Oceanography.