Das Projekt "Isotopic constraints on seasonal N2O dynamics in marine and lacustrine environments" wird/wurde gefördert durch: Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung. Es wird/wurde ausgeführt durch: Universität Basel, Umweltgeowissenschaften.Nitrous oxide (N2O) is now the third largest contributor to radiative forcing of the long-lived greenhouse gases. Human inputs of nitrogen (N), mainly as fertilizers, have stimulated the microbial N cycle transformations that are the dominant source of N2O. The partitioning between the anthropogenic and natural N2O sources is relatively well constrained at 7 and 11 Tg N/yr, respectively. However, large uncertainties remain in the relative contributions of terrestrial versus aquatic environments and with regards to the underlying biogeochemical controls on microbial N2O production. Such uncertainties present challenges for those devising and implementing N2O emissions policies, and make it difficult to interpret prehistoric atmospheric N2O fluctuations and predict the response of N2O production rates to future climate change. Aquatic N2O fluxes are often highly variable through time and space. The variation is likely modulated by fluctuations in the biogeochemical conditions, which may affect microbial N2O production pathways differentially. N2O can be produced by several processes, such as microbial nitrification (ammonia oxidation), denitrification, and nitrifier-denitrification, and multiple groups of microorganisms are involved. Yet, the exact environmental controls on temporal/spatial variations in net N2O production and the balance between the different pathways are still poorly constrained. It is highly probable that changes in the microbial processes that generate N2O are closely linked to seasonal changes in water productivity, organic matter remineralization rates, and in turn water-column redox-conditions. In this study we propose using incubation-based stable N-isotope tracer methods and natural N isotope measurements in dissolved N2O to identify and quantify specific N2O production pathways in two aquatic environments with strong seasonal N cycle dynamics: eutrophic Lake Lugano in southern Switzerland and the highly productive Benguela Upwelling region along the coast of southwestern Africa. Our main goals will be to shed light on the dynamics and controls on N2O production in two comparable environments. Within the frame of one postdoctoral project we propose to address the following research questions: - Hw much do ammonia oxidation, nitrifier-denitrification, and denitrification, respectively, contribute to N2O formation in Lake Lugano and the Benguela Upwelling? - Which biogeochemical factors control nitrifier-denitrification rates, and are there systematic differences between the marine and freshwater environment? (...)
Das Projekt "Mobilitaet von Genen in Klaerfloren" wird/wurde gefördert durch: Bundesministerium für Forschung und Technologie. Es wird/wurde ausgeführt durch: Bayer AG.Mit der Gen-Probe-Technik sind Untersuchungen zum Ueberleben, zur Konkurrenzfaehigkeit, zur Vermehrung und zu moeglichen Auswirkungen von fremden Mikroorganismen oder Genen auf das natuerliche Oekosystem moeglich. Gene, die fuer Schluesselenzyme im Abbau recalcitranter Stoffe codieren, eignen sich als Modelle fuer eine Risikoanalyse, da sie natuerlich vorkommen, da sich ihre Konzentration auf einfache Weise steuern laesst und da recalcitrante Verbindungen in Klaeranlagen oder verschiedenen Oekosystemen von erheblicher wirtschaftlicher und oekologischer Bedeutung sind. Die Untersuchungen sollen mit Gen-Proben durchgefuehrt werden, die spezifisch sind fuer haeufig vorhandene Abbaugene (Sulfonsaeuren, Isopropanol), seltene Abbaugene (Chloraromaten) und Gene schwer kultivierbarer Mikroorganismen (Ammoniakoxidation). Neben der Risikoabschaetzung fuer den Einsatz genmanipulierter Mikroorganismen sollen natuerliche Adaptionsmechanismen in Klaerfloren besser genutzt und Mikroorganismen mit neuen oder verbesserten Abbauleistungen erfasst werden.