title: Molecular and biogeochemical evidence for methane cycling beneath the western margin of the Greenland Ice Sheet.
abstract: Microbial processes that mineralize organic carbon and enhance solute production at the bed of polar ice sheets could be of a magnitude sufficient to affect global elemental cycles. To investigate the biogeochemistry of a polar subglacial microbial ecosystem, we analyzed water discharged during the summer of 2012 and 2013 from Russell Glacier, a land-terminating outlet glacier at the western margin of the Greenland Ice Sheet. The molecular data implied that the most abundant and active component of the subglacial microbial community at these marginal locations were bacteria within the order Methylococcales (59-100% of reverse transcribed (RT)-rRNA sequences). mRNA transcripts of the particulate methane monooxygenase (pmoA) from these taxa were also detected, confirming that methanotrophic bacteria were functional members of this subglacial ecosystem. Dissolved methane ranged between 2.7 and 83 μM in the subglacial waters analyzed, and the concentration was inversely correlated with dissolved oxygen while positively correlated with electrical conductivity. Subglacial microbial methane production was supported by δ(13)C-CH4 values between -64‰ and -62‰ together with the recovery of RT-rRNA sequences that classified within the Methanosarcinales and Methanomicrobiales. Under aerobic conditions, >98% of the methane in the subglacial water was consumed over ∼30 days incubation at ∼4 °C and rates of methane oxidation were estimated at 0.32 μM per day. Our results support the occurrence of active methane cycling beneath this region of the Greenland Ice Sheet, where microbial communities poised in oxygenated subglacial drainage channels could serve as significant methane sinks.
authors.affiliation: Department of Biological Sciences, Louisiana State University, Baton Rouge, LA, USA.
authors.forename: Markus
authors.initials: M
authors.lastname: Dieser
authors.affiliation: Department of Biological Sciences, Louisiana State University, Baton Rouge, LA, USA.
authors.forename: Erik L J E
authors.identifier: 000000028256156X
authors.initials: EL
authors.lastname: Broemsen
authors.affiliation: Applied Physics Laboratory, Polar Science Center, University of Washington, Seattle, WA, USA.
authors.forename: Karen A
authors.initials: KA
authors.lastname: Cameron
authors.affiliation: Department of Biological Sciences, Louisiana State University, Baton Rouge, LA, USA.
authors.forename: Gary M
authors.initials: GM
authors.lastname: King
authors.affiliation: Department of Biological Sciences, Louisiana State University, Baton Rouge, LA, USA.
authors.forename: Amanda
authors.initials: A
authors.lastname: Achberger
authors.affiliation: Applied Science Engineering and Technology Laboratory, Environment and Natural Resources Institute, University of Alaska Anchorage, Anchorage, AK, USA.
authors.forename: Kyla
authors.initials: K
authors.lastname: Choquette
authors.affiliation: Applied Science Engineering and Technology Laboratory, Environment and Natural Resources Institute, University of Alaska Anchorage, Anchorage, AK, USA.
authors.forename: Birgit
authors.initials: B
authors.lastname: Hagedorn
authors.affiliation: Department of Earth and Space Sciences, University of Washington, Seattle, WA, USA.
authors.forename: Ron
authors.initials: R
authors.lastname: Sletten
authors.affiliation: Applied Physics Laboratory, Polar Science Center, University of Washington, Seattle, WA, USA.
authors.forename: Karen
authors.initials: K
authors.lastname: Junge
authors.affiliation: Department of Biological Sciences, Louisiana State University, Baton Rouge, LA, USA.
authors.forename: Brent C
authors.initials: BC
authors.lastname: Christner
mesh_terms: D001419:Bacteria / Q000145:classification / Q000235:genetics / Q000302:isolation & purification; D017753:Ecosystem; D006116:Greenland; D046448:Ice Cover / Q000382:microbiology*; D008697:Methane / Q000032:analysis*; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D014867:Water / Q000737:chemistry; D014871:Water Microbiology
chemical_list: D012336:RNA, Ribosomal, 16S; D014867:Water; D008697:Methane
references.citation: Environ Microbiol. 2001 Sep;3(9):570-7
references.pmid: 11683867
references.citation: Int J Syst Evol Microbiol. 2005 Nov;55(Pt 6):2531-2538
references.pmid: 16280522
references.citation: FEMS Microbiol Ecol. 2012 Nov;82(2):254-67
references.pmid: 22168226
references.citation: Appl Environ Microbiol. 1994 Nov;60(11):3945-51
references.pmid: 16349429
references.citation: Environ Microbiol. 2009 Mar;11(3):609-15
references.pmid: 19278447
references.citation: Microb Ecol. 2009 Jan;57(1):25-35
references.pmid: 18592300
references.citation: ISME J. 2011 May;5(5):908-17
references.pmid: 21085198
references.citation: Mikrobiologiia. 2002 Jul-Aug;71(4):538-44
references.pmid: 12244726
references.citation: ISME J. 2013 Jul;7(7):1402-12
references.pmid: 23486249
references.citation: Int J Syst Evol Microbiol. 2011 Jan;61(Pt 1):45-52
references.pmid: 20154331
references.citation: Proc Natl Acad Sci U S A. 2011 Aug 2;108(31):12776-81
references.pmid: 21768380
references.citation: Appl Environ Microbiol. 2010 Sep;76(17):5773-84
references.pmid: 20622133
references.citation: Environ Microbiol Rep. 2010 Oct;2(5):685-92
references.pmid: 23766256
references.citation: ISME J. 2013 Nov;7(11):2061-8
references.pmid: 23823491
references.citation: Nature. 2012 Aug 30;488(7413):633-7
references.pmid: 22932387
references.citation: Appl Environ Microbiol. 2010 May;76(10):3228-35
references.pmid: 20348309
references.citation: Proc Natl Acad Sci U S A. 2013 Dec 3;110(49):19719-24
references.pmid: 24248343
references.citation: Appl Environ Microbiol. 2009 Dec;75(23):7537-41
references.pmid: 19801464
references.citation: Appl Environ Microbiol. 2005 Nov;71(11):6986-97
references.pmid: 16269734
references.citation: Extremophiles. 2012 Mar;16(2):255-65
references.pmid: 22241643
references.citation: Res Microbiol. 2011 Nov;162(9):832-47
references.pmid: 21704700
references.citation: Environ Microbiol. 2005 Aug;7(8):1127-38
references.pmid: 16011750
references.citation: Environ Microbiol. 2012 Nov;14(11):2998-3012
references.pmid: 23016868
references.citation: Environ Microbiol. 2009 Mar;11(3):640-56
references.pmid: 19278450
references.citation: FEMS Microbiol Ecol. 2007 Oct;62(1):24-31
references.pmid: 17725622
references.citation: ISME J. 2014 Nov;8(11):2305-16
references.pmid: 24739624