Das Projekt "Die steuernde Rolle von Infochemikalien bei der Funktion und Struktur von Nahrungsmitteln (SNIFFS)" wird vom Umweltbundesamt gefördert und von Eidgenössische Anstalt für Wasserversorgung, Abwasserreinigung und Gewässerschutz, Fachabteilung Hydrobiologie-Limnologie durchgeführt. The freshwater environment is influenced by antropogenic influences much more directly than the marine environment, which has lead to major problems with water quality in these systems. Earlier efforts to improve water quality via fish stock management (biomanipulation) in order to reduce the internal nutrient loadings of systems initially seemed promising. However, the lack of proper knowledge and understanding of the trophic interactions in freshwater systems has lead to costly failures. One possible reason for this is, that in food chain- and ecosystem studies, the attention has thus far been focused almost exclusively on the transfer of matter and energy between the different trophic levels, whereas the effect of information flow (by infochemicals) on the matter/energy flow has been largely ignored. The coupling of the flows of information and matter is the main objective of this project. Hence, the objectives are: 1) To describe quantitatively the matter/energy flow in a simple tritrophic food chain of two contrasting aquatic ecosystems in the catchment of the River Rhine; 2) to isolate and identify infochemicals affecting the structure and functioning of tritrophic food cains; 3) to measure the concentration dependence of individual and population respones to infochemicals in laboratory systems, and to measure the effects on the outcome of competition for resources; 4) to evaluate in model studies, employing individual-based models, the effects of different infochemicals on the transfer of matter and energy in the tritrophic food chain of two contrasting ecosystems on a larger temporal and spatial scale; and, 5) to propose guidelines for an improved integral water management. Prime Contractor: Koninklijke Nederlandse Akademie van Wetenschappen, Nederlands Instituut voor Oecologisch Onderzoek; Nieuwersluis; Netherlands.