Das Projekt "Biogeochemical fluxes in South-Alpine Lakes: Linking nitrogen and methane dynamics in lacustrine redox-transition zones using a combined stable isotope and molecular approach" wird vom Umweltbundesamt gefördert und von Universität Basel, Umweltgeowissenschaften durchgeführt. Bioavailable nitrogen (N) from anthropogenic sources is an important driver of lacustrine eutrophication. However, N loading in lakes is partially mitigated by microbially mediated processes that take place in redox transition zones (RTZ) within the water column and in sediments. RTZ are also sites of methane (CH4) and nitrous oxide (N2O) production and consumption. As a result of anthropogenic activities, emissions of these greenhouse gases to the atmosphere have significantly increased over the past decades. Lake Lugano is an excellent model system for an anthropogenically impacted lake that represents a hot-spot of quantitative redox-driven transformations involving the green house gases CH4 and N2O, as well as other N species acting as important macro nutrients. Previous studies have revealed that this lake represents an important sink for fixed N and that the anoxic deep-waters and sediments contain high concentrations of CH4. Through the application of stable isotopic, molecular ecological and geochemical techniques, laboratory cultivation and (radio-) tracer studies, the project will try (i) to understand the metabolic pathway involved in N and CH4 elimination in Lake Lugano, (ii) to assess the metabolic rates, at which the respective elimination processes take place, as well as their variability in time and space, (iii) to constrain the isotope effects associated with specific N and CH4 transformations, and (iv) to provide information about the microorganisms involved in these transformations. Thereby, a particularly focus is put on reactions that have essentially been neglected in lacustrine studies thus far, namely the anarobic oxidation of ammonium (anammox) and the anaerobic oxidation of methane (AOM). The project will provide the first comprehensive characterization of early diagenetic reactions in Lake Lugano. Moreover, it may allow insights into novel modes of autotrophic life in lakes. Finally, quantitative estimates of N and CH4 elimination in both the water column and sedimentary RTZ of Lake Lugano will be a prerequisite for ecosystem-scale N and C budgets. Thus, the project will provide important information that is directly pertinent to the health of Lake Lugano in particular, and eutrophied south alpine lakes in general.
Das Projekt "A GC-MS/GC-IRMS for the molecular-level analyses of organic matter and the isotopic characterization of inorganic and organic compounds in aquatic and terrestrial ecosystems" wird vom Umweltbundesamt gefördert und von Universität Basel, Umweltgeowissenschaften durchgeführt. A GC-MS/GC-IRMS for the molecular-level analyses of organic matter and the isotopic characterization of inorganic and organic compounds in aquatic and terrestrial ecosystems Stable isotopes represent a valuable means to constrain specific biogeochemical processes in natural environments. The main objective of the project is to develop an Environmental Laboratory for Aquatic and Terrestrial Biogeochemistry, which will support research that will make use of molecular-level characterization and (compound-specific) isotope ratio determination methods to assess a wide spectrum of biogeochemical transformations in the natural environment and in the laboratory, and to study sources and the fate of organic compounds in marine, freshwater, and soil systems. One of the major goals of the projects that make use of the new instrumental capacities is to understand the interactions of the bio- with the geo- and atmosphere with respect to the transport of organic materials and the transformation of inorganic and organic compounds by plants and microorganisms, which is of ultimate importance for the reduction of green house gases and the cycling of elements in aquatic and terrestrial ecosystems. A prime objective will be to use stable isotope measurements to constrain specific biogeochemical and metabolic processes, as well as sources, transport and degradation of organic matter in aquatic and terrestrial environments, and, in turn, to use these constraints to obtain improved estimates on global and regional C and N fluxes, in modern environments as well as in the past. Planned research themes include: I) using lipid biomarker approaches to study microbial communities in various marine and freshwater environments, II) characterizing organic matter components in lacustrine sediments as well as in soils, and identifying the mechanisms responsible for the longer-term sequestration and degradation of organic C and the emission of greenhouse gases, III) understanding the metabolic pathways of C and N during the symbiosis between microorganisms and plants, and IV) generating data sets for the isotopic composition of nitrate and other N species in various aquatic systems in order to characterize the controls on isotope fractionation of specific N cycle reactions. The spectrum of investigated ecosystems will range from Swiss soil and groundwater systems and small lakes to hydrothermal vent systems in the deep ocean, and the spatial scale of the planned research extends from enzyme biogeochemistry to ocean-scale circulation.