Magnitude of the Carbonate Dissolution Recycling Flux from Shallow Marine Carbonate Sediments: Evaluation from Pore Fluid and Sediment Geochemistry

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This project will investigate pore fluid and sediment geochemistry of shallow marine carbonate sediments from Florida Bay in order to assess their significance as recycling sites for calcium carbonate and organic matter. Results of a pilot study suggest that, contrary to prior assumptions, significant carbonate dissolution occurs in sediment pore fluids, driven by carbonic acid liberated from organic matter oxidation during sulfate reduction. The expanded investigation will evaluate this process across a wider range of environments and water depths than were accessible in the pilot study. The pore fluid chemistry (emphasis on Ca/Cl, degree of sulfate reduction, and carbonic acid system parameters) will be determined and sulfate reduction rates measured experimentally. Sediment organic carbon contents and carbon isotopic compositions of pore fluids will be determined to better constrain controls and consequences of sulfate reduction. Results will provide a rigorous assessment of the role shallow carbonate shelf deposits play in the oceanic cycles of calcium carbonate and organic matter. %%% The dissolution of calcium carbonate has long been thought to occur in deep water. The results of the pilot project, however, prove that much dissolution occurs in shallow water. This project will collect sedimentary cores from Florida Bay and begin geochemical analyses of the sediments immediately after their collection. This study will expand the knowledge of this important geochemical process to a new environment at greater depth to examine the role of other environmental parameters on the process.