Benthic Mineralization of Organic Matter on the Continental Rise and the Dissolution of CaCO 3 at the Deep Sea Floor

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This project is a continuation of a study of the cycling and diagenesis of organic matter at the sea floor. Knowledge of the deposition flux, cycling rate and burial rate of biogenic elements in sediments is required to assess the influence of ocean processes on global climate and to properly interpret the sedimentary record. Recent results from this project have raised questions about the dissolution of CaCO3 from sea floor sediments as a result of CO2 metabolically released in the pore water. Models of the alkalinity change in benthic flux chambers predict an alkalinity flux from the sediments, but the chamber data show little if any alkalinity flux during sea floor deployments. The goals of the present research are 1. To determine the influence of metabolically released CO2 on the dissolution of CaCO3 in deep sea sediments; 2. To determine the kinetic expression that accurately represents CaCO3 dissolution on the dea floor. The first part of the project consists of a short cruise to the continental slope off North Carolina to test a new High Pressure Sediment Sampler and some alterations to the benthic chambers by the P.I. The project is being coordinated with work on the same topic by Sayles and Martin (using a wire-line in situ whole core squeezer) and by Reimers (using PCO2 microelectrodes. The short test cruise provides an opportunity to test all the equipment and in addition may provide date on carbonate dissolution in an area where flux of organic carbon to the sea floor is predicted to be high, but bottom waters are saturated with CaCO3. The major portion of the work will be focussed on the Ceara Rise- guiana Basin region where the presence of Antarctic Bottom Water undersaturated with CaCO3 should cause significant measurable dissolution. The sea floor fluxes of carbonate system parameters measured by the in situ benthic flux chambers (this project) will be compared to the results from the other techniques.