Organic degradation, sulphate reduction and ammonium production in the sediments of Loch Eil, Scotland

The degradation of organic matter in sediments was studied by determining rates of sulphate reduction and ammonium production at 2 stations in Eil loch where there was an additional input of cellulose fibre from a pulp and paper mill. Sulphur-35 was used as a tracer to measure the sulphate reduction rate in field samples, and calculations of the carbon:nitrogen ratio of the organic substrate indicated a marine source. In jar incubation experiments, the rates of sulphate reduction were higher than those measured by the tracer technique but the rate decrease with depth was similar. The major effect of the cellulose input was on the sediment/water interface, where normal biogeochemical zones in the sediment were compressed, bringing the sulphate reducing zone to the surface at the station nearest to the pulp mill. The effect of the cellulose addition on the carbon and sulphur budgets was estimated. There are 55 references.