Wir untersuchen sowohl einzelne Prozesse in aquatischen Systemen als auch ganze Systeme natürlicher Gewässer. Neben der Grundlagenforschung und der interdisziplinären Systemanalyse stehen anwendungsnahe Projekte besonders im Fokus.
Processes affecting molecular and stable isotope compositions of sediment gas in estuarine waters along the southern Baltic coast (Poland)
This paper investigates the molecular and stable isotope compositions of sediment gases from seven coastal lakes along the southern Baltic coast in Poland. The aim is to extend the knowledge of the genesis and distribution of microbial gases in the zone of mixing of fresh and salt waters with special attention to the effect of salinity, climate-related seasonality, and vertical sediment mixing. We found differences in the compositions of gas between the studied lakes and within each lake. These differences are mainly controlled by lake water depth and the presence of macrophytes. Due to the dissolution of rising bubbles in highly oxygenated water, the concentrations of CH4 and CO2 show up to 67% decline along the water column in favor of N2 and O2. On the other hand, in vegetated parts of the lakes, the CH4 is depleted in favor of CO2, and the residual CH4 and CO2 are enriched in 13C. Despite the fact that the coastal lakes display highly oxidizing conditions in the water column and that the bottom sediments are mixed by wind waves the CH4 reveals rather low oxidation. On the basis of the CH4/N2 ratio we established that there are differences in the intensity of ebullition throughout the lakes. Higher intensities of ebullition were found in shallower parts of the lakes. Salinity has no effect on the stable C and H isotope composition of sediment gas. It seems, however, that salinity affects the molecular composition of hydrocarbons via preferential oxidation of CH4 under higher salinity conditions.
Woszczyk,M.; Kotarba,M.J.; Whiticar,M.; Schubert,C. (2016) Processes affecting molecular and stable isotope compositions of sediment gas in estuarine waters along the southern Baltic coast (Poland), Biogeochemistry, 26 pp., doi:10.1007/s10533-016-0275-8, Institutional Repository
Methanotrophy under versatile conditions in the water column of the ferruginous meromictic lake La Cruz (Spain)
Lakes represent a considerable natural source of methane to the atmosphere compared to their small global surface area. Methanotrophs in sediments and in the water column largely control methane fluxes from these systems, yet the diversity, electron accepting capacity, and nutrient requirements of these microorganisms have only been partially identified. Here, we investigated the role of electron acceptors alternative to oxygen and sulfate in microbial methane oxidation at the oxycline and in anoxic waters of the ferruginous meromictic Lake La Cruz, Spain. Active methane turnover in a zone extending well below the oxycline was evidenced by stable carbon isotope-based rate measurements. We observed a strong methane oxidation potential throughout the anoxic water column, which did not vary substantially from that at the oxic/anoxic interface. Both in the redox-transition and anoxic zones, only aerobic methane-oxidizing bacteria (MOB) were detected by fluorescence in situ hybridization and sequencing techniques, suggesting a close coupling of cryptic photosynthetic oxygen production and aerobic methane turnover. Additions of nitrate, nitrite and to a lesser degree iron and manganese oxides also stimulated bacterial methane consumption. We could not confirm a direct link between the reduction of these compounds and methane oxidation and we cannot exclude the contribution of unknown anaerobic methanotrophs. Nevertheless, our findings from Lake La Cruz support recent laboratory evidence that aerobic methanotrophs may be able to utilize alternative terminal electron acceptors under oxygen limitation.
Oswald,K.; Jegge,C.; Tischer,J.; Berg,J.; Brand,A.; Miracle,M.R.; Soria,X.; Vicente,E.; Lehmann,M.F.; Zopfi,J.; Schubert,C.J. (2016) Methanotrophy under versatile conditions in the water column of the ferruginous meromictic lake La Cruz (Spain), Frontiers in Microbiology, 7, article 1762 (16 pp.), doi:10.3389/fmicb.2016.01762, Institutional Repository
Der faszinierende Kivusee und das gelöste Methan in seinem Tiefenwasser könnten eine ganze Forschungsanstalt auf Trab halten. Mit unseren Forschungsprojekten versuchen wir, Grundlagen für eine nachhaltige und sichere Nutzung des Methans zu schaffen.
Abwasser ist mit antibiotikaresistenten Bakterien belastet.
Wir untersuchen ihre Ausbreitung in die Umwelt und Gegenmassnahmen.
Seen sind grosse Wärmespeicher. Inwiefern kann diese Wärme genutzt werden, um den Verbrauch von Brennstoffen und Elektrizität zum Heizen oder Kühlen zu vermindern?