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

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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.