Microbial Metabolism in Sediments of Coastal Inlets of the Southern Baltic Sea — Response to Gradients of Eutrophication

Abstract

Some effects of eutrophication on microbial metabolism and communities in sediments are described, with special emphasis on the microbial response to gradients of eutrophication in shallow-water coastal inlets of the southern Baltic Sea (Nordrugensche Bodden). It can be derived from the knowledge of the unique features of microbial colonisation and metabolism in sediments, that the structures of microbial communities and their metabolism are best suited to serve as indicators for eutrophication. Investigations of microbiological and chemical parameters along gradients of eutrophication in sediments of the bodden showed that microbial biomass and activities increased with increasing nutrient load. However, if organic carbon increases above certain concentrations, the buffer capacity is exhausted, and micro-organisms no longer respond to further increases in nutrient concentrations. Microbial processes, such as aerobic respiration, nitrification, de-nitrification, sulphate reduction and methanogenesis, are strongly influenced by eutrophication. Under the chronic stress of eutrophication, specific benthic microbial communities develop, already visible to the eye. Furthermore, the consequences of eutrophication on nutrient cycles of the sediments are discussed.