Projekt

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Nitrogen elimination pathways and associated isotope effects in Swiss eutrophic Lake Lugano

Titel Englisch Nitrogen elimination pathways and associated isotope effects in Swiss eutrophic Lake Lugano
Gesuchsteller/in Lehmann Moritz Felix
Nummer 129491
Förderungsinstrument Projektförderung (Abt. I-III)
Forschungseinrichtung Institut für Umweltgeowissenschaften Universität Basel
Hochschule Universität Basel - BS
Hauptdisziplin Andere Gebiete der Umweltwissenschaften
Beginn/Ende 01.04.2010 - 31.07.2013
Bewilligter Betrag 200'964.00
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Alle Disziplinen (7)

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

Keywords (16)

nitrogen cycle; denitrification; anammox; DNA analyses; stable isotopes; microbial community structures; biomarker; Lake Lugano; nitrogen; isotope effects; core incubations; sediment fluxes; nitrate; N2O; 15-N tracer; microbial ecology

Lay Summary (Englisch)

Lead
Lay summary
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. This project addresses 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?Combining hydrochemical, microbiological (phylogenetic/molecular genetic analyses, measurements of enzyme activities), with organic-geochemical (anammox lipid analysis) and isotopic techniques (natural abundance of nitrate, ammonium, nitrous oxide isotope ratios, as well as 15N tracer experiments), the project attempts to gain complementary information on specific N transformations and mechanisms of N2 loss in the Lake Lugano water column and sediments, on the microorganisms involved in these transformations, their relevance for the Lake Lugano nitrogen
Direktlink auf Lay Summary Letzte Aktualisierung: 21.02.2013

Verantw. Gesuchsteller/in und weitere Gesuchstellende

Mitarbeitende

Publikationen

Publikation
Differential N 2 O dynamics in two oxygen-deficient lake basins revealed by stable isotope and isotopomer distributions Differential N 2 O Dynamics in Two Lake Basins
(2016), Differential N 2 O dynamics in two oxygen-deficient lake basins revealed by stable isotope and isotopomer distributions Differential N 2 O Dynamics in Two Lake Basins, in Limnology and Oceanography, 61(5), 1735-1749.
Community N and O isotope fractionation by sulfide-dependent denitrification and anammox in a stratified lacustrine water column
(2014), Community N and O isotope fractionation by sulfide-dependent denitrification and anammox in a stratified lacustrine water column, in Geochimica et Cosmochimica Acta, 125, 551-563.
Partitioning between benthic and pelagic nitrate reduction in the Lake Lugano south basin
(2014), Partitioning between benthic and pelagic nitrate reduction in the Lake Lugano south basin, in Limnology and Oceanography, 59(4), 1421-1433.
Anaerobic ammonium oxidation (anammox) bacteria and sulfide-dependent denitrifiers coexist in the water column of a meromictic south-alpine lake
(2013), Anaerobic ammonium oxidation (anammox) bacteria and sulfide-dependent denitrifiers coexist in the water column of a meromictic south-alpine lake, in LIMNOLOGY AND OCEANOGRAPHY, 58(1), 1-12.
Nitrogen isotope effects induced by anammox bacteria
(2013), Nitrogen isotope effects induced by anammox bacteria, in Proceedings of the National Academy of Sciences, 110(47), 18994-18999.
NOx reduction is the main pathway for benthic N2O production in a eutrophic, monomictic south-alpine lake
(2013), NOx reduction is the main pathway for benthic N2O production in a eutrophic, monomictic south-alpine lake, in Biogeosciences Discussions, 10, 4969-4993.

Zusammenarbeit

Gruppe / Person Land
Formen der Zusammenarbeit
Fachhochschule Lugano Schweiz (Europa)
- Publikation
- Forschungsinfrastrukturen
MPI for Marine Microbiology Bremen Deutschland (Europa)
- vertiefter/weiterführender Austausch von Ansätzen, Methoden oder Resultaten
- Publikation
University of Nijmwegen Niederlande (Europa)
- vertiefter/weiterführender Austausch von Ansätzen, Methoden oder Resultaten
- Publikation

Wissenschaftliche Veranstaltungen

Aktiver Beitrag

Titel Art des Beitrags Titel des Artikels oder Beitrages Datum Ort Beteiligte Personen
Swiss Geoscience Meeting Vortrag im Rahmen einer Tagung Isotope effects during nitrogenous gas production by microbes in anaerobic environments 16.11.2012 Bern, Schweiz Lehmann Moritz Felix;
Goldschmidt Conference 2011 Poster Tracing N2O transformation pathways in a lake ecosystem by N2O isotopomer analysis 14.08.2011 Prague, Tschechische Republik Lehmann Moritz Felix; Wenk Christine;
12th Swiss Global Change Day Poster Tracing N2O transformation pathways in a lake ecosystem by N2O isotopomer analysis 19.04.2011 Bern, Schweiz Wenk Christine;
12th Swiss Global Change Day, Bern, Switzerland. Poster Benthic N2O production in the Lake Lugano South Basin: Rates and Processes 19.04.2011 Bern, Schweiz Wenk Christine;
4th Swiss Microbial Ecology Meeting Vortrag im Rahmen einer Tagung Anaerobic ammonium oxidation as potential fixed N elimination process in Lake Lugano, Switzerland 02.02.2011 Engelberg, Schweiz Wenk Christine; Zopfi Jakob;


Auszeichnungen

Titel Jahr
Hydrology/Limnology prize by the Swiss Society for Hydrology and Limnology (SGHL) 2014

Verbundene Projekte

Nummer Titel Start Förderungsinstrument
153055 Seasonal Dynamics of Coupled Nitrogen, Sulfur, and Carbon Cycling in Redox Transition Zones of Lake Lugano 01.11.2014 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)
147106 Isotopic constraints on seasonal N2O dynamics in marine and lacustrine environments 01.04.2013 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
137636 Microbes and oxidants involved in methane oxidation in South Alpine Lake Lugano 01.12.2011 Projektförderung (Abt. I-III)
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)

Abstract

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. Modes of bacterial 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 (DIN) species as a means to trace fluxes and transformations of N in aquatic systems, 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 are active in anaerobic portions of the lake. We propose to address the following main research questions:1.)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?2.)Which microorganisms are responsible for observed N transformations and what are their interactions?3.)What are the respective transformation rates and fluxes and how are they regulated? We propose one interdisciplinary PhD project that will combine microbiological (phylogenetic/molecular genetic analysis) with organic-geochemical (anammox lipid analysis) and isotopic techniques (natural abundance and 15N tracer experiments), to gain complementary information on specific N transformations and mechanisms of N2 loss in Lake Lugano sediments and in the water column, on the microorganisms involved in these transformations, their relevance for the Lake Lugano nitrogen budget, and their effects on the N isotope balances, both at the enzyme and ecosystem levels. The project will culminate in a mathematical model that will simulate microbial N-transformations within the lake sediments, allowing the assessment of the response of elemental and isotope budgets to changes in environmental conditions at various spatial and temporal scales. The project will provide extensive multidisciplinary training for one student at the graduate level in a field of high environmental relevance. The research proposed here will result in the first microbiological assessment of N transformations in Lake Lugano, and may help gaining 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. It will also provide useful information that is directly pertinent to the health of an important Swiss water body.
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