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Microbes and oxidants involved in methane oxidation in South Alpine Lake Lugano

English title Microbes and oxidants involved in methane oxidation in South Alpine Lake Lugano
Applicant Lehmann Moritz
Number 137636
Funding scheme Project funding (Div. I-III)
Research institution Institut für Umweltgeowissenschaften Universität Basel
Institution of higher education University of Basel - BS
Main discipline Hydrology, Limnology, Glaciology
Start/End 01.12.2011 - 30.11.2012
Approved amount 60'784.00
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All Disciplines (2)

Discipline
Hydrology, Limnology, Glaciology
Geochemistry

Lay Summary (English)

Lead
Lay summary

Previously, we generated a comprehensive data set that provides compelling biogeochemical evidence for an anaerobic mode of methane oxidation in the North Basin of Lake Lugano ("Biogeochemical fluxes in South-Alpine Lakes: Linking nitrogen and methane dynamics in lacustrine redox-transition zones using a combined stable isotope and molecular approach" (SNF 121861; Dec. 2008 - Nov. 2011). The dominance of monoenoic fatty acids in deep waters of the North Basin with very low δ13C-values, together with the finding of 14CH4 tracer turnover in incubations of water depth from 175m and below, indicate the incorporation of methane-derived carbon into bacterial biomass well below the redoxcline.

Thus far, no compounds typically associated with anaerobic methanotrophic archaea (e.g. archaeol) could be detected, suggesting potential bacterial anaerobic methanotrophy in the water column of Lake Lugano. Yet, the phylogenetic identity of the microbes that perform AOM, as well as the possible terminal electron acceptor for AOM still needs further evaluation. First sulphate reduction rate measurements suggest that sulphate reduction cannot account for the observed AOM.  In this project we will conduct sampling campaigns and laboratory incubation experiments, combining radio-label, stable isotopic, and molecular (16S rRNA gene diversity, qPCR, FISH) analyses, with the specific goals 1) to assess the role of oxidized metal species (FeIII; MnIV) or NOx involved as oxidant in methane oxidation in the water column of Lake Lugano, and 2) to further constrain the identity of microbes that perform methane oxidation by linking microbial identity and organism-level C-isotope signatures.

Quantitative estimates of CH4 elimination in the water column of Lake Lugano will be a prerequisite for ecosystem-scale C budgets. The analyses of bacterial and archaeal functional genes are expected to yield valuable insight into the ecological structure of both the permanent (North Basin) and transitional (South Basin) water column redox-transition zones in Lake Lugano. Moreover, estimates of isotope effects of specific C 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.


Direct link to Lay Summary Last update: 21.02.2013

Responsible applicant and co-applicants

Employees

Name Institute

Publications

Publication
Micro-aerobic bacterial methane oxidation in the chemocline and anoxic water column of deep south-Alpine Lake Lugano (Switzerland)
Blees Jan, Niemann Helge, Wenk Christine B., Zopfi Jakob, Schubert Carsten J., Kirf Mathias K., Veronesi Mauro L., Hitz Carmen, Lehmann Moritz F. (2014), Micro-aerobic bacterial methane oxidation in the chemocline and anoxic water column of deep south-Alpine Lake Lugano (Switzerland), in Limnology and Oceanography, 59(2), 311-324.

Collaboration

Group / person Country
Types of collaboration
LSA Lugano/FH Lugano (Dr. M. Veronesi and Dr. M. Simona) Switzerland (Europe)
- Research Infrastructure

Associated projects

Number Title Start Funding scheme
129491 Nitrogen elimination pathways and associated isotope effects in Swiss eutrophic Lake Lugano 01.04.2010 Project funding (Div. 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 Project funding (Div. I-III)
159878 Microbes and biogeochemical processes associated to methane oxidation at deep sea brines and highly active cold seep systems 01.04.2015 Project funding (Div. I-III)

Abstract

With this proposal, we seek funding for a 12-month extension of the PhD project "Biogeochemical fluxes in South-Alpine Lakes: Linking nitrogen and methane dynamics in lacustrine redox-transition zones using a combined stable isotope and molecular approach" (SNF 121861; Dec. 2008 - Nov. 2011). The main objectives of SNF project 121861 are to investigate the concentration, distribution and isotopic composition of CH4 and lipid biomarkers in Lake Lugano, a eutrophic lake in southern Switzerland, and to apply microbiological and radio-isotope measurements to Lake Lugano water-column samples in order to: (i) understand the metabolic pathway involved in CH4 elimination and production in Lake Lugano, (ii) assess the metabolic rates, at which the respective elimination processes take place, as well as their variability in time and space, (iii) constrain the isotope effects associated with specific CH4 transformations, and (iv) gain information about the microorganisms involved in these transformations. During the first 2 years of the project, we generated a comprehensive data set that provides compelling biogeochemical evidence for an anaerobic mode of methane oxidation in the North Basin of Lake Lugano. Methane oxidation occurs with a C-isotope effect (approx. 7‰) that is significantly lower than average estimates for aerobic methane oxidation. The dominance of monoenoic fatty acids in deep waters of the North Basin with very low d13C-values, together with the finding of 14CH4 tracer turnover in incubations of water depth from 175m and below, indicate the incorporation of methane-derived carbon into bacterial biomass well below the redoxcline. Thus far, no compounds typically associated with anaerobic methanotrophic archaea (e.g. archaeol) could be detected, suggesting potential bacterial anaerobic methanotrophy in the water column of Lake Lugano. Yet, the phylogenetic identity of the microbes that perform AOM, as well as the possible terminal electron acceptor for AOM still needs further evaluation. First sulphate reduction rate measurements suggest that sulphate reduction cannot account for the observed AOM. Here we propose additional sampling campaigns and laboratory incubation experiments, combining radio-label, stable isotopic, and molecular (16S rRNA gene diversity, qPCR, FISH) analyses, with the specific goals 1) to assess the role of oxidized metal species (FeIII; MnIV) or NOx involved as oxidant in methane oxidation in the water column of Lake Lugano, and 2) to further constrain the identity of microbes that perform methane oxidation by linking microbial identity and organism-level C-isotope signatures.Quantitative estimates of CH4 elimination in the water column of Lake Lugano will be a prerequisite for ecosystem-scale C budgets. The analyses of bacterial and archaeal functional genes are expected to yield valuable insight into the ecological structure of both the permanent (North Basin) and transitional (South Basin) water column redox-transition zones in Lake Lugano. Moreover, estimates of isotope effects of specific C 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.
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