Collaborative Research: How temporal changes in river discharge and storms affect the source and age distribution of sedimentary organic carbon across a river-dominated margin

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Continental margins are dynamic regions that receive inputs of organic carbon derived from both terrestrial and marine sources. Once introduced by the Mississippi or fixed on the Louisiana shelf, POC is carried along the shelf, decomposed, buried, or transported to deeper regions in the Gulf of Mexico. Based on coastal primary production estimates and riverine inputs, only 20-50% of the organic carbon in coastal waters off the Mississippi is actually buried in Louisiana shelf sediments, and 40% of that buried carbon is of terrestrial origin. Thus, the fate of 50-80% of the carbon fraction delivered by the Mississippi that cannot be accounted for in shelf sediments remains a key question in developing a North American carbon budget. Under this funding, the PIs propose a combined approach of compound-specific stable and radiocarbon isotopic techniques and biomarker distributions to evaluate fates and transport of organic carbon in the Mississippi River delta shelf and slope. The working hypothesis of this study is that seasonal changes in the composition and age of SOC across the Louisiana shelf/slope are largely determined by pulses in terrestrially- and marine-derived organic carbon which occur at distinct time periods controlled by changes in Mississippi River discharge and storm energy.