Fate of organic carbon reaching the deep sea floor: a status report

The rates of organic carbon oxidation by O2, NO3−, MnO2, Fe2O3 and SO4− have been calculated for five pelagic Pacific and Atlantic sites using simple diffusion-reaction models. O2 everywhere oxidizes > 90% of the raining Corg; the fraction oxidized by the secondary oxidants decreases as the rain rate of organic C to the seafloor decreases. A large fraction of the Corg escaping oxidation by O2 is oxidized by the secondary oxidants. Hence while these oxidants play a small role in remineralization, they are important in regulating the burial of organic matter and the consequent removal from the oceans of reduced carbon and nutrients.