Early diagenesis of organic matter in surface sediments

Only a small fraction of the organic matter produced in surface waters sinks out of the euphotic zone and reaches the deep-sea floor. Again only a minor fraction is buried and thus forms the sedimentary record. The remainder is mineralized on its way down the water column or near the sediment-water interface.

In deep-sea sediments, this decay of organic matter takes place primarily by oxidation through oxygen. The decomposition rate can therefore be estimated from measurements with microelectrodes, which record the gradient of dissolved oxygen in the surface few millimeters of the sediment. The study of the cycling of many other components requires the collection of pore water.