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Fine-Scale Community Structure Analysis of ANME in Nyegga Sediments with High and Low Methane Flux.

Roalkvam I, Dahle H, Chen Y, Jørgensen SL, Haflidason H, Steen IH - Front Microbiol (2012)

Bottom Line: These data were compared with previously obtained data from the more active G11 pockmark, characterized by higher methane flux.The stratification was over a wider spatial region and at greater depth in the core with lower methane flux, and the total 16S rRNA copy numbers were two orders of magnitude lower than in the sediments at G11 pockmark.Given that the ANME-2a/b population could be sustained in less active seepage areas, this subgroup could be potential seed populations in newly developed methane-enriched environments.

View Article: PubMed Central - PubMed

Affiliation: Center for Geobiology, Department of Biology, University of Bergen Bergen, Norway.

ABSTRACT
To obtain knowledge on how regional variations in methane seepage rates influence the stratification, abundance, and diversity of anaerobic methanotrophs (ANME), we analyzed the vertical microbial stratification in a gravity core from a methane micro-seeping area at Nyegga by using 454-pyrosequencing of 16S rRNA gene tagged amplicons and quantitative PCR. These data were compared with previously obtained data from the more active G11 pockmark, characterized by higher methane flux. A down core stratification and high relative abundance of ANME were observed in both cores, with transition from an ANME-2a/b dominated community in low-sulfide and low methane horizons to ANME-1 dominance in horizons near the sulfate-methane transition zone. The stratification was over a wider spatial region and at greater depth in the core with lower methane flux, and the total 16S rRNA copy numbers were two orders of magnitude lower than in the sediments at G11 pockmark. A fine-scale view into the ANME communities at each location was achieved through operational taxonomical units (OTU) clustering of ANME-affiliated sequences. The majority of ANME-1 sequences from both sampling sites clustered within one OTU, while ANME-2a/b sequences were represented in unique OTUs. We suggest that free-living ANME-1 is the most abundant taxon in Nyegga cold seeps, and also the main consumer of methane. The observation of specific ANME-2a/b OTUs at each location could reflect that organisms within this clade are adapted to different geochemical settings, perhaps due to differences in methane affinity. Given that the ANME-2a/b population could be sustained in less active seepage areas, this subgroup could be potential seed populations in newly developed methane-enriched environments.

No MeSH data available.


Overview map of the Norwegian Sea and the surrounding land areas with the location of the Nyegga study area and the HMMV (Håkon Mosby Mud Volcano). The position of the main pathway of the warm surface current NWAC (Norwegian Water Atlantic Current) is outlined (A). Location of the CN03 target site and the pockmark G11 at the Nyegga area (B). A high-resolution TOPAS profile (Line GS07-148-126) across the CN03 gas seeping area with inserted the location of the studied core GS08-155-15GC (C).
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Figure 1: Overview map of the Norwegian Sea and the surrounding land areas with the location of the Nyegga study area and the HMMV (Håkon Mosby Mud Volcano). The position of the main pathway of the warm surface current NWAC (Norwegian Water Atlantic Current) is outlined (A). Location of the CN03 target site and the pockmark G11 at the Nyegga area (B). A high-resolution TOPAS profile (Line GS07-148-126) across the CN03 gas seeping area with inserted the location of the studied core GS08-155-15GC (C).

Mentions: The Nyegga area is located on the upper Mid-Norwegian continental slope, at the northeast flank of the Storegga Slide (Figure 1), and is characterized by a high density of pockmarks and fluid seepage structures (Evans et al., 1996; Hustoft et al., 2010; Reiche et al., 2011). The area has been a field for multidisciplinary studies on gas hydrates, authigenic carbonates, fluid flow, and pore-water geochemistry the last decade with a special focus on the active micro-seeping area around pockmarks G11 and CN03 (also called CNE03; Hovland et al., 2005; Hovland and Svensen, 2006; Mazzini et al., 2006; Chen et al., 2010; Hustoft et al., 2010; Ivanov et al., 2010; Plaza-Faverola et al., 2010, 2011; Vaular et al., 2010; Reiche et al., 2011). Recent 2D/3D seismic and multibeam mapping of the Nyegga area has revealed an area with a high density of pockmark structures, many with underlying gas blanking areas extending down to a pronounced bottom simulating reflector (BSR) at 250–300 m depth below seafloor (mbsf; Bünz et al., 2003; Hustoft et al., 2007, 2009, 2010; Hjelstuen et al., 2010; Plaza-Faverola et al., 2010; Reiche et al., 2011). During a cruise with R/V G.O.Sars to the Nyegga area in August of 2008, the 3 m long gravity core GS08-155-15GC (referred to as 15GC hereafter) was retrieved from the CN03 area (64°45.274′N 05°04.088′E) at 725 m water depth. The ambient seawater temperature was measured with CTD to be between −0.6 and −0.7°C. After retrieval of 15GC, one half of the core was immediately sampled for detailed microbial diversity studies and geochemical measurements while the other half was stored at 4°C as an archive for non-destructive MST and XRF core scanner studies in laboratories on land. Rhizon samplers were used to extract pore-water from eight horizons throughout the core; at 24, 57, 89, 129, 171, 244, 258, and 290 cm below seafloor (cmbsf). The subsamples were preserved in glass vials and kept cool until they were analyzed according to the approach in Chen et al. (2010) in order to determine the concentration of dissolved sulfate () and total dissolved hydrogen sulfide (ΣH2S). Subsamples for DNA extraction were aseptically retrieved at 10, 30, 50, 80, 100, 120, 140, 160, 180, 200, 220, 240, 255, 270, and 300 cmbsf (±0.5 cm) by using sterile 1 mL tip cut plastic syringes before they were snap-frozen in liquid N2 and stored at −80°C.


Fine-Scale Community Structure Analysis of ANME in Nyegga Sediments with High and Low Methane Flux.

Roalkvam I, Dahle H, Chen Y, Jørgensen SL, Haflidason H, Steen IH - Front Microbiol (2012)

Overview map of the Norwegian Sea and the surrounding land areas with the location of the Nyegga study area and the HMMV (Håkon Mosby Mud Volcano). The position of the main pathway of the warm surface current NWAC (Norwegian Water Atlantic Current) is outlined (A). Location of the CN03 target site and the pockmark G11 at the Nyegga area (B). A high-resolution TOPAS profile (Line GS07-148-126) across the CN03 gas seeping area with inserted the location of the studied core GS08-155-15GC (C).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3375579&req=5

Figure 1: Overview map of the Norwegian Sea and the surrounding land areas with the location of the Nyegga study area and the HMMV (Håkon Mosby Mud Volcano). The position of the main pathway of the warm surface current NWAC (Norwegian Water Atlantic Current) is outlined (A). Location of the CN03 target site and the pockmark G11 at the Nyegga area (B). A high-resolution TOPAS profile (Line GS07-148-126) across the CN03 gas seeping area with inserted the location of the studied core GS08-155-15GC (C).
Mentions: The Nyegga area is located on the upper Mid-Norwegian continental slope, at the northeast flank of the Storegga Slide (Figure 1), and is characterized by a high density of pockmarks and fluid seepage structures (Evans et al., 1996; Hustoft et al., 2010; Reiche et al., 2011). The area has been a field for multidisciplinary studies on gas hydrates, authigenic carbonates, fluid flow, and pore-water geochemistry the last decade with a special focus on the active micro-seeping area around pockmarks G11 and CN03 (also called CNE03; Hovland et al., 2005; Hovland and Svensen, 2006; Mazzini et al., 2006; Chen et al., 2010; Hustoft et al., 2010; Ivanov et al., 2010; Plaza-Faverola et al., 2010, 2011; Vaular et al., 2010; Reiche et al., 2011). Recent 2D/3D seismic and multibeam mapping of the Nyegga area has revealed an area with a high density of pockmark structures, many with underlying gas blanking areas extending down to a pronounced bottom simulating reflector (BSR) at 250–300 m depth below seafloor (mbsf; Bünz et al., 2003; Hustoft et al., 2007, 2009, 2010; Hjelstuen et al., 2010; Plaza-Faverola et al., 2010; Reiche et al., 2011). During a cruise with R/V G.O.Sars to the Nyegga area in August of 2008, the 3 m long gravity core GS08-155-15GC (referred to as 15GC hereafter) was retrieved from the CN03 area (64°45.274′N 05°04.088′E) at 725 m water depth. The ambient seawater temperature was measured with CTD to be between −0.6 and −0.7°C. After retrieval of 15GC, one half of the core was immediately sampled for detailed microbial diversity studies and geochemical measurements while the other half was stored at 4°C as an archive for non-destructive MST and XRF core scanner studies in laboratories on land. Rhizon samplers were used to extract pore-water from eight horizons throughout the core; at 24, 57, 89, 129, 171, 244, 258, and 290 cm below seafloor (cmbsf). The subsamples were preserved in glass vials and kept cool until they were analyzed according to the approach in Chen et al. (2010) in order to determine the concentration of dissolved sulfate () and total dissolved hydrogen sulfide (ΣH2S). Subsamples for DNA extraction were aseptically retrieved at 10, 30, 50, 80, 100, 120, 140, 160, 180, 200, 220, 240, 255, 270, and 300 cmbsf (±0.5 cm) by using sterile 1 mL tip cut plastic syringes before they were snap-frozen in liquid N2 and stored at −80°C.

Bottom Line: These data were compared with previously obtained data from the more active G11 pockmark, characterized by higher methane flux.The stratification was over a wider spatial region and at greater depth in the core with lower methane flux, and the total 16S rRNA copy numbers were two orders of magnitude lower than in the sediments at G11 pockmark.Given that the ANME-2a/b population could be sustained in less active seepage areas, this subgroup could be potential seed populations in newly developed methane-enriched environments.

View Article: PubMed Central - PubMed

Affiliation: Center for Geobiology, Department of Biology, University of Bergen Bergen, Norway.

ABSTRACT
To obtain knowledge on how regional variations in methane seepage rates influence the stratification, abundance, and diversity of anaerobic methanotrophs (ANME), we analyzed the vertical microbial stratification in a gravity core from a methane micro-seeping area at Nyegga by using 454-pyrosequencing of 16S rRNA gene tagged amplicons and quantitative PCR. These data were compared with previously obtained data from the more active G11 pockmark, characterized by higher methane flux. A down core stratification and high relative abundance of ANME were observed in both cores, with transition from an ANME-2a/b dominated community in low-sulfide and low methane horizons to ANME-1 dominance in horizons near the sulfate-methane transition zone. The stratification was over a wider spatial region and at greater depth in the core with lower methane flux, and the total 16S rRNA copy numbers were two orders of magnitude lower than in the sediments at G11 pockmark. A fine-scale view into the ANME communities at each location was achieved through operational taxonomical units (OTU) clustering of ANME-affiliated sequences. The majority of ANME-1 sequences from both sampling sites clustered within one OTU, while ANME-2a/b sequences were represented in unique OTUs. We suggest that free-living ANME-1 is the most abundant taxon in Nyegga cold seeps, and also the main consumer of methane. The observation of specific ANME-2a/b OTUs at each location could reflect that organisms within this clade are adapted to different geochemical settings, perhaps due to differences in methane affinity. Given that the ANME-2a/b population could be sustained in less active seepage areas, this subgroup could be potential seed populations in newly developed methane-enriched environments.

No MeSH data available.