Comparative Study of Methanogenic Pathways in the Sediments of Thermokarst and Polygenetic Yamal Lakes

Microbiology - Comparative study of methanogen diversity and potential activity of different methanogenic pathways in the sediments of young thermokarst and mature polygenetic Yamal lakes was...     

Erratum to: On the Possibility of Aerobic Methane Production by Pelagic Microbial Communities of the Laptev Sea

Microbiology - An Erratum to this paper has been published: https://doi.org/10.1134/S0026261721110011     

On the Possibility of Aerobic Methane Production by Pelagic Microbial Communities of the Laptev Sea

Microbiology - The taxonomic diversity and metabolic activity of microbial communities in the Laptev Sea water column above and outside the methane seep field were studied. The concentrations of...     

Sulfate reduction, methanogenesis, and methane oxidation in the upper sediments of the Vistula and Curonian Lagoons, Baltic Sea

Microbiological, biogeochemical, and isotope geochemical investigations of the upper sediments of the Vistula and Curonian lagoons, Baltic Sea, were carried out. High content of organic matter in the sediments was responsible for the high numbers (over 10¹⁰ cells cm^?3) and activity of heterotrophic microorganisms. The calculated integral rates of dark CO₂ assimilation for the upper 30 cm of the sediments varied 12.5 to 38.8 mmol m^?2 day^?1 and were somewhat higher in the Curonian Lagoon than in the Vistula Lagoon. Integral rates of sulfate reduction were higher in the more saline Vistula Lagoon. Rapid consumption of sulfates of the pore water resulted in intensified methanogenesis, with significantly higher rates detected in the silts of the Curonian Lagoon. High rates of methanogenesis in the Curonian Lagoon correlated with higher methane levels in its upper sediments and near-bottom water. The highest rates of methane oxidation were detected in the uppermost sediment horizons (oxidized or slightly reduced), which was an indication of the barrier role of aerobic methanotrophic bacteria. The calculated methane flows from the sediments into the water column were 0.45 and 0.007 mmol m^?2 day^?1 for the Vistula and Curonian Lagoons, respectively. Low methane flow from the sediments of the Curonian Lagoon resulted probably from the specific weather (wind) conditions during sampling. The near-stormy conditions in the Curonian Lagoon caused sediment detachment, resulting in methane release into the water column.     

Microbiological Processes of the Carbon and Sulfur Cycles at Cold Methane Seeps of the North Atlantic

Functioning of microbial communities in surface sediments of the Haakon Mosby underwater mud volcano (lat. 72°N) and in gas seepage fields of the Vestnesa Ridge was investigated using Mir-1 and Mir-2 deep-sea submersibles during the 40th voyage of the research vessel Academician Mstislav Keldysh. Large areas of sedimentary deposits of the Haakon Mosby mud volcano (HMMV) and pockmarks of the Vestnesa Ridge (VR) are covered with bacterial mats 0.1 to 0.5 cm thick. The microbial community making up bacterial mats of the HMMV was dominated by large filamentous bacteria with filaments measuring up to 100 m in length and 2 to 8 m in width. The occurrence of rosettes allowed the observed filamentous bacteria to be referred to the morphologically similar genera Leucothrix or Thiothrix. Three morphological types of filamentous bacteria were identified in bacterial mats covering VR pockmarks. Filaments of type one are morphologically similar with representatives of the genera Thioploca or Desmanthos. Type two filaments had numerous inclusions of sulfur and resembled representatives of the genus Thiothrix. The third morphological type was constituted by single filaments made up of tightly connected disk-like cells and can be assigned to the genus Beggiatoa. The rates of methane oxidation (up to 1570 l C/(dm³ day)) and sulfate reduction (up to 17 mg S/(dm³day)) measured in the surface sediments of HMMV and VR were close to the maximum rates of these processes observed in heavily polluted regions of the northwestern shelf of the Black Sea. High rates of microbiological processes correlated with the high number of bacteria. The rate of methane production in sediments studied was notably lower and ranged from 0.1 to 3.5 CH₄/(dm³ day). Large areas of the HMMV caldera were populated by pogonophoras, represented by the two species Sclerolinum sp. and Oligobrachia sp. The mass development of Sclerolinum sp. in the HMMV caldera was by the activity of aerobic methane-oxidizing bacteria localized inside the cells of these animals. Bacterial cells were also found in the trophosome tissue of Oligobrachia sp., but in cells of these bacteria, we did not observe the membrane structures typical of methanotrophs. The localization pattern of pogonophoras on the surface of reduced sediments suggests that the predominant bacteria in Oligobrachia tissues are sulfur-oxidizing endosymbionts.     

Microbial processes of the carbon and sulfur cycles in the Chukchi Sea

The research performed in August 2004 within the framework of the Russian-American Long-term Census of the Arctic (RUSALCA) resulted in the first data concerning the rates of the key microbial processes in the water column and bottom sediments of the Bering strait and the Chukchi Sea. The total bacterial counts in the water column varied from 30 × 10³ cells ml^?1 in the northern and eastern parts to 245 × 10³ cells ml^?1 in the southern part. The methane content in the water column of the Chukchi sea varied from 8 nmol CH₄l^?1 in the eastern part of the sea to 31 nmol CH₄l^?1 in the northern part of the Herald Canyon. Microbial activity occurred in the upper 0–3 cm of the bottom sediments; the methane formation rate varied from 0.25 to 16 nmol CH₄dm^?3 day^?1. The rates of methane oxidation varied from 1.61 to 14.7 nmol CH₄dm^?3 day^?1. The rates of sulfate reduction varied from 1.35 to 16.2 μmol SO ₄ ^2? dm^?1 day^?1. The rate of methane formation in the sediments increased with depth, while sulfate reduction rates decreased (less than 1 μmol SO ₄ ^2? dm^?3 day^?1). These high concentrations of biogenic elements and high rates of microbial processes in the upper sediment layers suggest a specific type of trophic chain in the Chukchi Sea. The approximate calculated balance of methane emission from the water column into the atmosphere is from 5.4 to 57.3 μmol CH₄m^?2 day^?1.     

Phylogenetic diversity in sulphate-reducing bacterial communities from oxidised and reduced bottom sediments of the Barents Sea

In the bottom sediments from a number of the Barents Sea sites, including coastal areas of the Novaya Zemlya, Franz Josef Land, and Svalbard archipelagos, sulphate reduction rates were measured and the phylogenetic composition of sulphate-reducing bacterial (SRB) communities was analysed for the first time. Molecular genetic analysis of the sequences of the 16S rRNA and dsrB genes (the latter encodes the β-subunit of dissimilatory (bi)sulphite reductase) revealed significant differences in the composition of bacterial communities in different sampling stations and sediment horizons of the Barents Sea depending on the physicochemical conditions. The major bacteria involved in reduction of sulphur compounds in Arctic marine bottom sediments belonged to Desulfobulbaceae, Desulfobacteraceae, Desulfovibrionaceae, Desulfuromonadaceae, and Desulfarculaceae families, as well as to uncultured clades SAR324 and Sva0485. Desulfobulbaceae and Desulfuromonadaceae predominated in the oxidised (E_h = 154–226 mV) upper layers of the sediments (up to 9% and 5.9% from all reads of the 16S rRNA gene sequences in the sample, correspondingly), while in deeper, more reduced layers (E_h = ?210 to ?105 mV) the share of Desulfobacteraceae in the SRB community was also significant (up to 5%). The highest relative abundance of members of Desulfarculaceae family (3.1%) was revealed in reduced layers of sandy-clayey sediments from the Barents Sea area affected by currents of transformed (mixed, with changed physicochemical characteristics) Atlantic waters.

     

Microbial Community of a Marine Meromictic Trough (Biofilter Bay) in the Kandalaksha Bay,White Sea

Microbiology - The composition of microbial communities and the rates of microbial processes in the water column of a meromictic trough in the Biofilter Bay, Kandalaksha Bay, White Sea were...     

Seasonal changes in the structure of the anoxygenic phototrophic bacterial community in Lake Mogilnoe, a relict lake on Kil'din Island in the Barents Sea

An anaerobic phototrophic bacterial community in Lake Mogilnoe, a relict lake on Kil'din Island in the Barents Sea, was studied in June 1999 and September 2001. Irrespective of the season, the upper layer of the anaerobic zone of this lake had a specific species composition of sulfur phototrophic bacteria, which were dominated by the brown-colored green sulfur bacterium Chlorobium phaeovibrioides. The maximum number of phototrophic sulfur bacteria was observed in June 1999 at a depth of 9 m, which corresponded to a concentration of bacteriochlorophyll (Bchl) e equal to 4.6 mg/l. In September 2001, the maximum concentration of this pigment (3.4 mg/l) was found at a depth of 10 m. In both seasons, the concentration of Bchl a did not exceed 3 microg/l. Purple sulfur bacteria were low in number, which can be explained by their poor adaptation to the hydrochemical and optical conditions of the Lake Mogilnoe water. In June 1999, the water contained a considerable number of Pelodictyon phaeum microcolonies and Prosthecochloris phaeoasteroides cell chains, which was not the case in September 2001. A 16S rDNA-based phylogenetic analysis of pure cultures of phototrophic bacteria isolated from the lake water confirmed that the bacterial community is dominated by Chl. phaeovibrioides and showed the presence of three minor species, Thiocvstis gelatinosa, Thiocapsa sp., and Thiorhodococcus sp., the last of which is specific to Lake Mogilnoe.