title: A novel, multi-layered methanotrophic microbial mat system growing on the sediment of the Black Sea.
abstract: A novel microbially diverse type of 1- to 5-cm-thick mat performing anaerobic oxidation of methane (AOM) and covering several square metres of the seafloor was discovered in the Black Sea at 180 m water depth. Contrary to other AOM-mat systems of the Black Sea these floating mats are not associated to free gas and are not stabilized by authigenic carbonates. However, supply of methane is ensured by the horizontal orientation of the mats acting as a cover of methane enriched fluids ascending from the underlying sediments. Thorough investigation of their community composition by molecular microbiology and lipid biomarkers, metabolic activities and elemental composition showed that the mats provide a clearly structured system with extracellular polymeric substances (EPS) building the framework of the mats. The top black zone, showing high rates of AOM (15 mumol g(dw) (-1) day(-1)), was dominated by ANME-2, while the following equally active pink layer was dominated by ANME-1 Archaea. The lowest AOM activity (2 mumol g(dw) (-1) day(-1)) and cell numbers were found in the greyish middle part delimited towards the sediment by a second pink, ANME-1-dominated and sometimes a black outer layer (ANME-2). Our work clearly shows that the different microbial populations are established along defined chemical gradients such as methane, sulfate or sulfide.
authors.affiliation: Section Geomicrobiology, Federal Institute for Geosciences and Natural Resources, Stilleweg 2, 30655 Hannover, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Krüger
authors.forename: Martin
authors.initials: M
authors.lastname: Blumenberg
authors.forename: Sabine
authors.initials: S
authors.lastname: Kasten
authors.forename: Andrea
authors.initials: A
authors.lastname: Wieland
authors.forename: Layla
authors.initials: L
authors.lastname: Känel
authors.forename: Jan-Hendrik
authors.initials: JH
authors.lastname: Klock
authors.forename: Walter
authors.initials: W
authors.lastname: Michaelis
authors.forename: Richard
authors.initials: R
authors.lastname: Seifert
mesh_terms: D001105:Archaea / Q000302:isolation & purification; D001267:Atlantic Ocean; D001419:Bacteria / Q000302:isolation & purification; D017753:Ecosystem; D019015:Geologic Sediments / Q000382:microbiology*; D008697:Methane / Q000378:metabolism*; D012623:Seawater / Q000382:microbiology*; D013431:Sulfates / Q000378:metabolism
chemical_list: D013431:Sulfates; D008697:Methane