Organic carbon fluxes, degradation, and accumulation in an anoxic basin: Sediment trap results from the Cariaco Basin

Organic carbon fluxes were measured in the anoxic water column of the Caria co Basin under varying levels of primary productivity. Our results indicate that water column degradation of fresh organic matter in this anoxic setti ng is similar to what has been previously observed in the open ocean. Addit ionally, the rate at which carbon is consumed increases as primary producti vity increases. These findings support the hypothesis that sulfate reductio n is as efficient as aerobic respiration in degrading labile organic matter and that an anoxic water column does not necessarily result in an enhanced delivery of organic carbon to the sea floor. We estimate that 1-2% of the organic carbon produced at the surface leaches the seafloor and that approx imately 50% of this is preserved in the sediments. This burial efficiency i s comparable to that previously reported for both oxic and anoxic settings, and with sedimentation rates similar to that in Cariaco Basin.