title: Methanogenic activity and diversity in the centre of the Amsterdam Mud Volcano, Eastern Mediterranean Sea.
abstract: Marine mud volcanoes are geological structures emitting large amounts of methane from their active centres. The Amsterdam mud volcano (AMV), located in the Anaximander Mountains south of Turkey, is characterized by intense active methane seepage produced in part by methanogens. To date, information about the diversity or the metabolic pathways used by the methanogens in active centres of marine mud volcanoes is limited. (14)C-radiotracer measurements showed that methylamines/methanol, H(2)/CO(2) and acetate were used for methanogenesis in the AMV. Methylotrophic methanogenesis was measured all along the sediment core, Methanosarcinales affiliated sequences were detected using archaeal 16S PCR-DGGE and mcrA gene libraries, and enrichments of methanogens showed the presence of Methanococcoides in the shallow sediment layers. Overall acetoclastic methanogenesis was higher than hydrogenotrophic methanogenesis, which is unusual for cold seep sediments. Interestingly, acetate porewater concentrations were extremely high in the AMV sediments. This might be the result of organic matter cracking in deeper hotter sediment layers. Methane was also produced from hexadecanes. For the most part, the methanogenic community diversity was in accordance with the depth distribution of the H(2)/CO(2) and acetate methanogenesis. These results demonstrate the importance of methanogenic communities in the centres of marine mud volcanoes.
authors.affiliation: Department of Marine Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA. clazar@email.unc.edu
authors.forename: Cassandre Sara
authors.initials: CS
authors.lastname: Lazar
authors.forename: R
authors.initials: R
authors.lastname: John Parkes
authors.forename: Barry A
authors.initials: BA
authors.lastname: Cragg
authors.forename: Stephane
authors.initials: S
authors.lastname: L'Haridon
authors.forename: Laurent
authors.initials: L
authors.lastname: Toffin
mesh_terms: D001105:Archaea / Q000145:classification* / Q000235:genetics / Q000378:metabolism*; D044822:Biodiversity; D019015:Geologic Sediments / Q000737:chemistry / Q000382:microbiology*; D008522:Mediterranean Sea; D008697:Methane / Q000378:metabolism*; D017019:Methanosarcinaceae / Q000145:classification / Q000235:genetics / Q000378:metabolism; D019640:Methanosarcinales / Q000145:classification / Q000235:genetics / Q000378:metabolism; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics
chemical_list: D012336:RNA, Ribosomal, 16S; D008697:Methane