Effect of oxygen on the degradability of organic matter in subtidal and intertidal sediments of the North Sea area

The effect of oxygen on the degradation of sedimentary organic matter has b een determined for 6 subtidal stations and 3 intertidal stations in the Nor th Sea area. The stations were selected to cover a range of organic matter lability and sediment texture (and hence concentrations of organic matter). Slurry incubations revealed that at low mineralisation rates, aerobic mine ralisation is significantly faster than anaerobic mineralisation, irrespect ive of the degree of lability of organic matter. A complementary incubation experiment with sediment rich in organic carbon mixed with varying proport ions of organically poor sediments confirmed the enhanced aerobic mineralis ation at low mineralisation levels. It is proposed that oxygen-enhanced deg radation occurs at low mineralisation levels at which bacterial biomass pro duction becomes limiting.