Kurzfassung

Dead organic material is a significant source of energy and nutrients for food-webs and is fundamentally important for the biogeochemical nutrient cycling. Microorganisms are crucial to decompose this material in both terrestrial and aquatic ecosystems. Microbial activity, however, is determined by their surrounding environment and can be stimulated in the presence of labile organic carbon (= priming effect). In streams, this labile organic carbon can be provided by photoautotrophs. However,...Dead organic material is a significant source of energy and nutrients for food-webs and is fundamentally important for the biogeochemical nutrient cycling. Microorganisms are crucial to decompose this material in both terrestrial and aquatic ecosystems. Microbial activity, however, is determined by their surrounding environment and can be stimulated in the presence of labile organic carbon (= priming effect). In streams, this labile organic carbon can be provided by photoautotrophs. However, little is understood on the processes that trigger this priming effect in streams – particularly the relevance of the theoretical framework developed for soil ecosystems needs verification. Therefore, the present study aims at understanding the relevance of nutrient-levels in the substrate and the water body as well as the intermediary role of r-strategists for the real priming realized by k-strategists using well-controlled laboratory experiments. During these experiments, variables describing the microorganism community composition and their functional role such as organic matter decomposition or greenhouse gas production will allow for the determination of relevant processes. Moreover, the significance of spatial proximity between source and receptor of labile organic carbon will be assessed during field experiments. Finally, the current theoretical framework of nutrient cycling in running water ecosystems will be advanced by considering both biological and biogeochemical processes.» weiterlesen» einklappen