title: Methanotrophy under Versatile Conditions in the Water Column of the Ferruginous Meromictic Lake La Cruz (Spain).
abstract: 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 fluorescencein situhybridization 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.
authors.affiliation: Department of Surface Waters - Research and Management, Swiss Federal Institute of Aquatic Science and TechnologyKastanienbaum, Switzerland; Department of Environmental Systems Science, Institute of Biogeochemistry and Pollutant Dynamics, ETH Zurich, Swiss Federal Institute of TechnologyZurich, Switzerland.
authors.forename: Kirsten
authors.initials: K
authors.lastname: Oswald
authors.affiliation: Department of Surface Waters - Research and Management, Swiss Federal Institute of Aquatic Science and TechnologyKastanienbaum, Switzerland; School of Architecture, Civil and Environmental Engineering, EPFL, Swiss Federal Institute of TechnologyLausanne, Switzerland.
authors.forename: Corinne
authors.initials: C
authors.lastname: Jegge
authors.affiliation: Department of Environmental Sciences, University of Basel Basel, Switzerland.
authors.forename: Jana
authors.initials: J
authors.lastname: Tischer
authors.affiliation: Department of Biogeochemistry, Max Planck Institute for Marine Microbiology Bremen, Germany.
authors.forename: Jasmine
authors.initials: J
authors.lastname: Berg
authors.affiliation: Department of Surface Waters - Research and Management, Swiss Federal Institute of Aquatic Science and TechnologyKastanienbaum, Switzerland; Department of Environmental Systems Science, Institute of Biogeochemistry and Pollutant Dynamics, ETH Zurich, Swiss Federal Institute of TechnologyZurich, Switzerland.
authors.forename: Andreas
authors.initials: A
authors.lastname: Brand
authors.affiliation: Department of Microbiology and Ecology, Cavanilles Institute of Biodiversity and Evolutionary Biology, University of Valencia Burjassot, Spain.
authors.forename: María R
authors.initials: MR
authors.lastname: Miracle
authors.affiliation: Department of Microbiology and Ecology, Cavanilles Institute of Biodiversity and Evolutionary Biology, University of Valencia Burjassot, Spain.
authors.forename: Xavier
authors.initials: X
authors.lastname: Soria
authors.affiliation: Department of Microbiology and Ecology, Cavanilles Institute of Biodiversity and Evolutionary Biology, University of Valencia Burjassot, Spain.
authors.forename: Eduardo
authors.initials: E
authors.lastname: Vicente
authors.affiliation: Department of Environmental Sciences, University of Basel Basel, Switzerland.
authors.forename: Moritz F
authors.initials: MF
authors.lastname: Lehmann
authors.affiliation: Department of Environmental Sciences, University of Basel Basel, Switzerland.
authors.forename: Jakob
authors.initials: J
authors.lastname: Zopfi
authors.affiliation: Department of Surface Waters - Research and Management, Swiss Federal Institute of Aquatic Science and Technology Kastanienbaum, Switzerland.
authors.forename: Carsten J
authors.initials: CJ
authors.lastname: Schubert
keywords: aerobic methanotrophs; anoxic hypolimnion; ferruginous; meromixis; methane oxidation; oxycline