Description: Das Projekt "Nitrogen elimination pathways and associated isotope effects in Swiss eutrophie Lake Lugano (2010-2013)" wird vom Umweltbundesamt gefördert und von Universität Basel, Institut für Umweltgeowissenschaften, Forschungsgruppe Biogeographie durchgeführt. Bioavailable nitrogen (N) from natural and 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 nitrous oxide (N2O) production and consumption. As a result of anthropogenic activities, emission of this greenhouse gas to the atmosphere has significantly increased over the past decades. The role of lakes as a terrestrial sink for fixed N is still poorly constrained. Furthermore, modes of suboxic N2 production other than canonical denitrification (e.g., the anaerobic oxidation of ammonium, or anammox) have barely been investigated in lakes, and the microbial communities involved in N transformations in lacustrine RTZ are mostly unknown. Nitrogen isotope ratios can provide important constraints on natural N cycles. In order to use natural abundance stable isotope ratios of dissolved inorganic N species as a means to trace fluxes and transformations of N in aquatic systems, however, it is imperative to understand the isotope effects associated with these specific N transformations. This will also provide information on the transformations themselves. Yet, the possible impact of N2 production processes other than denitrification on global and regional N-isotope budgets has been ignored thus far. Lake Lugano is an excellent model biosystem for an anthropogenically impacted lake. Previous studies have revealed that this lake represents an important sink for fixed N. In addition, they indicate the presence of suboxic consumption of ammonium and, thus, suggest that 'non-traditional' N2 production processes (e.g., anammox) are active in anaerobic portions of the lake. We propose to address the following main research questions: What are the different metabolic pathways of suboxic N2 production in the Lake Lugano water column and in sediments? What are the associated N-isotope effects? What are the respective transformation rates and fluxes? Which microorganisms are responsible for observed N transformations? The research proposed here will result in the first comprehensive characterization of N cycling reactions in Lake Lugano. Moreover, this research may help gain insights into novel modes of autotrophic life in lakes. Quantitative estimates of N elimination in both the water column and sedimentary RTZ of Lake Lugano will be a prerequisite for ecosystem-scale N budgets and will be integrated in box-model simulations. Moreover, estimates of isotope effects of specific N transformations in the modern lake will provide the basis for paleolimnological extrapolation. Thus, the proposed research will help us address biogeochemical processes that are important for the general understanding of a complex ecosystem, both today and in the past.
Types:
SupportProgram
Origin: /Bund/UBA/UFORDAT
Tags: Denitrifikation ? Ammonium ? Stickstoffelimination ? Tierhaltungsanlage ? Eutrophierung ? Seen ? Basel ? Lugano ? Seensediment ? Stickstoff ? Main ? Schweiz ? Treibhausgasemission ? Biogeografie ? Lachgas ? Biosystem ? Hochrechnung ? Isotop ? Konsum ? Oxidation ? Standortwahl ? Studie ? Mikroorganismen ? Sediment ? Wasser ? Ökosystemforschung ? Atmosphäre ? Wasserhaushalt ?
License: cc-by-nc-nd/4.0
Language: Deutsch
Time ranges: 2010-04-01 - 2013-03-31
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