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Seasonal Dynamics of Coupled Nitrogen, Sulfur, and Carbon Cycling in Redox Transition Zones of Lake Lugano

Titel Englisch Seasonal Dynamics of Coupled Nitrogen, Sulfur, and Carbon Cycling in Redox Transition Zones of Lake Lugano
Gesuchsteller/in Zopfi Jakob
Nummer 153055
Förderungsinstrument Projektförderung (Abt. I-III)
Forschungseinrichtung Institut für Umweltgeowissenschaften Universität Basel
Hochschule Universität Basel - BS
Hauptdisziplin Hydrologie, Limnologie, Glaziologie
Beginn/Ende 01.11.2014 - 31.10.2018
Bewilligter Betrag 527'605.00
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Alle Disziplinen (6)

Disziplin
Hydrologie, Limnologie, Glaziologie
Experimentelle Mikrobiologie
Umweltforschung
Oekologie
Andere Gebiete der Umweltwissenschaften
Geochemie

Keywords (9)

anammox; nitrogen cycle; Lake Lugano; N2O; microbial community structures; microbial ecology; sulfur cycling; stable isotopes; denitrification

Lay Summary (Deutsch)

Lead
Stickstoff (N) ist ein für alle Lebewesen essentielles Element, doch übermässiger Gebrauch von Düngemitteln sowie der Eintrag von gebundenem N aus Haushalten kann zur Eutrophierung von Flüssen und Seen führen. Im Allgemeinen wird die Denitrifikation, die mikrobielle Umwandlung von Nitrat in gasförmigen Stickstoff (N2), als bedeutendster Prozess angesehen, welcher N wieder aus dem Ökosystem entfernt und somit der Eutrophierung entgegenwirkt. Doch neu entdeckte N-umsetzende Mikroorganismen und Prozesse deuten darauf hin, dass diese Sichtweise unvollständig ist. So konnte im Rahmen des Vorgängerprojektes nachgewiesen werden, dass Anammox, die anaerobe Oxidation von Ammonium zu N2, im Luganersee vorkommt und zur N-Elimination beiträgt.
Lay summary

Im Rahmen dieses Projektes soll unter Anwendung biogeochemischer, Isotopen-geochemischer und mikrobiologischer Methoden die saisonale Dynamik, Regulation und Interaktionen verschiedener N-umsetzender Prozesse untersucht werden. Der Luganersee dient dabei als Modellsystem für einen anthropogen beeinflussten eutrophen See. Das Ziel dieser Arbeit ist ein vollständigeres Verständnis des biogeochemischen N-Kreislaufs und dessen Anbindung an andere Stoffkreisläufe im Luganersee sowie in aquatischen Systemen allgemein. 

Direktlink auf Lay Summary Letzte Aktualisierung: 10.09.2014

Verantw. Gesuchsteller/in und weitere Gesuchstellende

Mitarbeitende

Verbundene Projekte

Nummer Titel Start Förderungsinstrument
129491 Nitrogen elimination pathways and associated isotope effects in Swiss eutrophic Lake Lugano 01.04.2010 Projektförderung (Abt. I-III)
170876 Advanced understanding of autotrophic nitrogen removal and associated N2O emissions in mixed nitritation-anammox systems through combined stable ISOtopic and MOLecular constraints (ISOMOL) 01.09.2017 Sinergia
121861 Biogeochemical fluxes in South-Alpine Lakes: Linking nitrogen and methane dynamics in lacustrine redox-transition zones using a combined stable isotope and molecular approach 01.12.2008 Projektförderung (Abt. I-III)
147106 Isotopic constraints on seasonal N2O dynamics in marine and lacustrine environments 01.04.2013 Projektförderung (Abt. I-III)
159197 Environmental controls on N2O production by ammonium oxidizing bacteria in marine and lacustrine environments - a stable isotopic approach 01.04.2015 Projektförderung (Abt. I-III)

Abstract

Nitrogen (N) is an essential element for all living organisms, but extensive use of fertilizer and additional input of reactive N of domestic origin has led to the eutrophication of rivers, lakes, and coastal marine ecosystems. Denitrification, the anaerobic respiratory reduction of nitrate to N2, has traditionally been seen as the most important process converting reactive N to N2. Recent observations in natural environments and the discovery of new groups of N-transforming microorganisms with previously unknown metabolisms and unexpected links to the sulfur, iron or manganese cycles suggests, however, that the canonical concepts of certain redox pathways are incomplete, casting doubt on the current general understanding of the global N cycle. Lake Lugano is an excellent model system for an anthropogenically impacted lake and represents a hot-spot for redox-driven transformations including nitrogen, carbon, sulfur, and iron. The main objectives of the previous SNF project “Nitrogen elimination pathways and associated isotope effects in Swiss eutrophic Lake Lugano” were to investigate the microbial processes responsible for reactive N elimination in Lake Lugano, to quantify reaction rates within the water column, and to constrain the N isotope signatures of specific N cycling reactions. In that project we have identified some of the “non-traditional” N-elimination processes, and we found that anammox bacteria and sulphide-dependent denitrifiers coexist in the same water layers of the permanently stratified north basin, whereas “traditional” organotrophic denitrification was negligible. The dynamic conditions in the south basin were more conducive to organotrophic denitrification, and associated with net N2O production and accumulation in near-bottom waters. The output from the precursor project has catalyzed a multitude of new questions, which we plan to address. In this regard, the interdisciplinary research program proposed here is essentially a direct and logic continuation of the SNF No 129491. Still within the scope of the original project, we propose a research program for two PhD projects: 1.Research Project A investigates the dynamics, environmental controls, and isotope fingerprints of coupled microbial nitrogen-sulfur transformation in the RTZ of the Lake Lugano North Basin2.Research Project B aims at understanding the sedimentary nitrogen cycling and associated microbial community dynamics in the South Basin, with particular focus on links to other element cyclesUsing a combination of biogeochemical, isotope, and microbiological tools we propose to identify the mechanisms that regulate the relative importance of the different N loss processes, anammox, chemolithotrophic- and organotrophic denitrification in the RTZ of the north basin and to elucidate possibly synergistic interactions between anammox bacteria and the chemolithotrophe denitrifiers. Moreover we will determine the so far unknown N and O isotope fractionation during S-dependent nitrate-reduction in laboratory experiments. Extremely high transient accumulation of N2O and inconsistencies regarding nitrate uptake have been observed in the previous project, illustrating the lack of understanding of N-cycling in the iron-rich sediments of the south basin. By means of high-resolution porewater-N profiling with microsensors, the first measurements of their kind in Lake Lugano, and supplementary 15N isotope tracer experiments, we will identify and quantify the pathways and rates of benthic N-transformations. These time-resolved biogeochmical data, including fluxes, as well as measured and modeled process rates, will serve as contextual data for exploring the seasonal dynamics of the sedimentary microbial communities. The planned study will investigate microbial dynamics associated with reactions that were relatively unknown a decade or so ago, and barely investigated in freshwater environments. Moreover, our research may help gain insights into novel forms of symbiotic associations between chemolithotrophic bacteria in lakes, efficiently coupling the lacustrine nitrogen and sulfur cycles. The proposed research is thus not only relevant for the understanding and quantification of reactive N-loss in Lake Lugano. It will result in a better comprehension of N turnover pathways in general.
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