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Sources and Distribution of Organic Matter in Sediments of the Louisiana Continental Shelf
Citation:
Jarvis, B., J. Lehrter, R. Devereux, D. Beddick, AND D. Yates. Sources and Distribution of Organic Matter in Sediments of the Louisiana Continental Shelf. Presented at ASLO 2013 Aquatic Sciences Meeting, February 17 - 22, 2013.
Impact/Purpose:
This abstract submission is for presentation of a poster at ASLO summarizing the sediment radiochemistry and stable isotope results from the GM1009 sediment cruise.
Description:
Both riverine and marine sources of organic matter (OM) contribute to sediment organic pools, and either source can contribute significantly to sediment accumulation, burial, and remineralization rates on river dominated continental shelf systems. For the Louisiana continental shelf (LCS), OM deposition, metabolism, and burial are important components of conceptual models for coastal hypoxia and the shelf carbon budget. However, spatial variability in deposition rates and distribution of OM sources (terrestrial vs. marine) remain unconstrained across the depth range at which hypoxia generally occurs on the LCS. This study quantified sediment accumulation rates and OM composition on four cross-shelf transects west of the Mississippi River delta. Sediment accumulation rates decreased with westward distance from the Southwest Pass (0.09-0.46 cm yr-1), resulting in organic carbon burial rates between 1.3-24.5 g m-2 yr-1. Sediment particulate organic carbon stable isotope values varied between -25‰ to -20‰, and were generally enriched offshore. Carbon isotope and C:N ratios indicated decreasing terrigenous influence with distance offshore. These results further constrain spatial patterns of terrigenous and marine OM accumulation within the LCS.