title: [Microbiological and biogeochemical processes in a pockmark of the Gdansk depression, Baltic Sea].
abstract: Comprehensive microbiological and biogeochemical investigation of a pockmark within one of the sites of gas-saturated sediments in the Gdansk depression, Baltic Sea was carried out during the 87th voyage of the Professor Shtokman research vessel. Methane content in the near-bottom water and in the underlying sediments indicates stable methane flow from the sediment into the water. In the 10-m water layer above the pockmark, apart from methane anomalies, elevated numbers of microorganisms and enhanced rates of dark CO2 fixation (up to 1.15 micromol C/(1 day)) and methane oxidation (up to 2.14 nmol CH4/(1 day)) were revealed. Lightened isotopic composition of suspended organic matter also indicates high activity of the near-bottom microbial community. Compared to the background stations, methane content in pockmark sediments increased sharply from the surface to 40-60 ml/dm3 in the 20-30cm horizon. High rates of bacterial sulfate reduction (SR) were detected throughout the core (0-40 cm); the maximum of 74 micromol/(dm3 day) was located in subsurface horizons (15-20 cm). The highest rates of anaerobic methane oxidation (AMO), up to 80 micromol/(dm3 day), were detected in the same horizon. Good coincidence of the AMO and SR profiles with stoichiometry close to 1:1 is evidence in favor of a close relation between these processes performed by a consortium of methanotrophic archaea and sulfate-reducing bacteria. Methane isotopic composition in subsurface sediments of the pockmark (from -53.0 to -56.5% per hundred) does not rule out the presence of methane other than the biogenic methane from the deep horizons of the sedimentary cover.
authors.forename: N V
authors.initials: NV
authors.lastname: Pimenov
authors.forename: M O
authors.initials: MO
authors.lastname: Ul'ianova
authors.forename: T A
authors.initials: TA
authors.lastname: Kanapatski
authors.forename: V V
authors.initials: VV
authors.lastname: Sivkov
authors.forename: M V
authors.initials: MV
authors.lastname: Ivanov
mesh_terms: D000693:Anaerobiosis; D001105:Archaea / Q000302:isolation & purification / Q000378:metabolism*; D001419:Bacteria / Q000302:isolation & purification / Q000378:metabolism*; D002245:Carbon Dioxide / Q000032:analysis / Q000378:metabolism; D002247:Carbon Isotopes / Q000032:analysis; D015169:Colony Count, Microbial; D019015:Geologic Sediments / Q000032:analysis / Q000382:microbiology*; D008697:Methane / Q000032:analysis / Q000378:metabolism*; D009792:Oceans and Seas; D010084:Oxidation-Reduction; D011044:Poland; D012623:Seawater / Q000737:chemistry* / Q000382:microbiology*; D013431:Sulfates / Q000032:analysis / Q000378:metabolism; D014871:Water Microbiology
chemical_list: D002247:Carbon Isotopes; D013431:Sulfates; D002245:Carbon Dioxide; D008697:Methane