Organic matter degradation and carbonate dissolution in surficial deep-sea sediments control benthic fluxes to sea water and the extent of organic carbon and calcium carbonate preservation in the ocean. These processes are studied using microelectrodes to measure gradients of conductivity, oxygen and pH across the sediment-water interface. A modelling study of certain pH results to date reveals that the rate the in situ of calcite dissolution is pressure-dependent and the rate constant is several orders of magnitude less than laboratory-determined values. A recent field comparison between fluxes calculated from microelectrode oxygen and pH data, was not observed in the lander fluxes. This result departs from present perceptions about the mechanisms of CaCo3 dissolution on the sea floor, is and will be tested by exploring mechanisms that might explain the discrepancy. The research will focus on a transect of microelectrode profiles and lander fluxes across the saturation horizon on the Ceara Rise in the eastern equatorial Atlantic Ocean. The study is a collaborative experiment with Dr. Richard Jahnke (OCE-9201896) who is carrying out a benthic flux experiment in this area. Diagenesis mechanisms and the integrity of pH determinations will be tested by measuring pCO2 across the sediment-water interface using a fiber-optic sensor constructed during the past year.
