MINERALIZATION OF ORGANIC NITROGEN AND CARBON (FISH FOOD) ADDED TO ANOXIC SEDIMENT MICROCOSMS - ROLE OF SULFATE REDUCTION

Substrate (fish food) was added to gas-tight bags containing sediment, with and without molybdate. Amino-nitrogen (amino-N) was measured by high-performance liquid chromatography. The oxidation of 3 representat ive C-14-labelled amino acids (glutamic acid, alanine and arginine) wa s measured and the mean decay rate constant was used to calculate turn over rates of amino-N. Concentrations of dissolved organic nitrogen, d issolved organic carbon, total inorganic carbon and ammonium were meas ured during 28 d of incubation. Inhibition of sulphate-reducing activi ty gave a 4.2-fold decrease in the rate of ammonium production and a 4 .5-fold decrease in the rate of amino acid turnover. These results sug gest an active participation of sulphate-reducing bacteria in amino ac id oxidation.