Many of the reactions and biogeochemical processes that occur in the marine environment are related directly or indirectly to the mineralization of organic matter. Decomposition of organic matter is responsible for the recycling of essential nutrients, for the oxygen balance of the ocean and its sediments and for most early diagenetic processes. The rate at which organic matter is mineralized varies over orders of magnitude and depends on, among other factors, the composition and orgin of the organic material being degraded and on the environmental conditions. However, direct relationship between organic matter decomposition rates and organic matter composition or between mineralization rates and organic matter decomposition pathways (e.g. oxic versus anoxic) are difficult to establish.