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Stratified community responses to methane and sulfate supplies in mud volcano deposits: insights from an in vitro experiment.

Zhang Y, Maignien L, Stadnitskaia A, Boeckx P, Xiao X, Boon N - PLoS ONE (2014)

Bottom Line: Numerous studies on marine prokaryotic communities have postulated that a process of anaerobic oxidation of methane (AOM) coupled with sulfate reduction (SR) is the main methane sink in the world's oceans.Moreover, the incubation conditions below the SMTZ favor the growth of methanotrophic archaeal group ANME-2 compared to ANME-1, and promote the rapid growth and high diversity of bacterial communities.Our results provide direct evidence of the mechanisms by which deep AOM processes can affect carbon cycling in the deep biosphere and global methane biochemistry.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Microbial Metabolism, State Key Laboratory of Ocean Engineering, Shanghai Jiao Tong University, Shanghai, People's Republic of China; Laboratory of Microbial Ecology and Technology, Ghent University, Gent, Belgium.

ABSTRACT
Numerous studies on marine prokaryotic communities have postulated that a process of anaerobic oxidation of methane (AOM) coupled with sulfate reduction (SR) is the main methane sink in the world's oceans. AOM has also been reported in the deep biosphere. But the responses of the primary microbial players in eliciting changes in geochemical environments, specifically in methane and sulfate supplies, have yet to be fully elucidated. Marine mud volcanoes (MVs) expel a complex fluid mixture of which methane is the primary component, forming an environment in which AOM is a common phenomenon. In this context, we attempted to identify how the prokaryotic community would respond to changes in methane and sulfate intensities, which often occur in MV environments in the form of eruptions, diffusions or seepage. We applied an integrated approach, including (i) biochemical surveys of pore water originated from MV, (ii) in vitro incubation of mud breccia, and (iii) prokaryotic community structure analysis. Two distinct AOM regions were clearly detected. One is related to the sulfate methane transition zone (SMTZ) at depth of 30-55 cm below the sea floor (bsf); the second is at 165-205 cm bsf with ten times higher rates of AOM and SR. This finding contrasts with the sulfide concentrations in pore waters and supports the suggestion that potential AOM activity below the SMTZ might be an important methane sink that is largely ignored or underestimated in oceanic methane budget calculations. Moreover, the incubation conditions below the SMTZ favor the growth of methanotrophic archaeal group ANME-2 compared to ANME-1, and promote the rapid growth and high diversity of bacterial communities. These incubation conditions also promote the increase of richness in bacterial communities. Our results provide direct evidence of the mechanisms by which deep AOM processes can affect carbon cycling in the deep biosphere and global methane biochemistry.

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The microbial activity and community structures as an effect of 176 days of in vitro incubation.A) The overall SR/AOM activities; B/E) the bacterial/archaeal communities' similarity with respect to sediment depth; C/F) the bacterial/archaeal communities' evenness expressed as a Gini value; D/G) the bacterial/archaeal communities' richness. Legend for A: the solid dot is the SR rate, and the circle is the AOM rate. Legend for B-G: the solid dot is the value at day 0, and the circle is the value at day 176.
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pone-0113004-g004: The microbial activity and community structures as an effect of 176 days of in vitro incubation.A) The overall SR/AOM activities; B/E) the bacterial/archaeal communities' similarity with respect to sediment depth; C/F) the bacterial/archaeal communities' evenness expressed as a Gini value; D/G) the bacterial/archaeal communities' richness. Legend for A: the solid dot is the SR rate, and the circle is the AOM rate. Legend for B-G: the solid dot is the value at day 0, and the circle is the value at day 176.

Mentions: A deeper AOM active zone was defined at 165–205 cm bsf. In the presence of methane and sulfate, this interval exhibited an immediate production of sulfide, which remained active throughout the incubation experiment (Fig. 3). The highest SR activity, 24.7 nmol/ml rs/d, was detected at a depth of 195 cm bsf. This sediment layer also showed AOM activity, with rates of 1.4–6.2 nmol/ml rs/d (Fig. 4A). The remainder of the mud breccia section revealed no SR or AOM activities (Fig. 3).


Stratified community responses to methane and sulfate supplies in mud volcano deposits: insights from an in vitro experiment.

Zhang Y, Maignien L, Stadnitskaia A, Boeckx P, Xiao X, Boon N - PLoS ONE (2014)

The microbial activity and community structures as an effect of 176 days of in vitro incubation.A) The overall SR/AOM activities; B/E) the bacterial/archaeal communities' similarity with respect to sediment depth; C/F) the bacterial/archaeal communities' evenness expressed as a Gini value; D/G) the bacterial/archaeal communities' richness. Legend for A: the solid dot is the SR rate, and the circle is the AOM rate. Legend for B-G: the solid dot is the value at day 0, and the circle is the value at day 176.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4231134&req=5

pone-0113004-g004: The microbial activity and community structures as an effect of 176 days of in vitro incubation.A) The overall SR/AOM activities; B/E) the bacterial/archaeal communities' similarity with respect to sediment depth; C/F) the bacterial/archaeal communities' evenness expressed as a Gini value; D/G) the bacterial/archaeal communities' richness. Legend for A: the solid dot is the SR rate, and the circle is the AOM rate. Legend for B-G: the solid dot is the value at day 0, and the circle is the value at day 176.
Mentions: A deeper AOM active zone was defined at 165–205 cm bsf. In the presence of methane and sulfate, this interval exhibited an immediate production of sulfide, which remained active throughout the incubation experiment (Fig. 3). The highest SR activity, 24.7 nmol/ml rs/d, was detected at a depth of 195 cm bsf. This sediment layer also showed AOM activity, with rates of 1.4–6.2 nmol/ml rs/d (Fig. 4A). The remainder of the mud breccia section revealed no SR or AOM activities (Fig. 3).

Bottom Line: Numerous studies on marine prokaryotic communities have postulated that a process of anaerobic oxidation of methane (AOM) coupled with sulfate reduction (SR) is the main methane sink in the world's oceans.Moreover, the incubation conditions below the SMTZ favor the growth of methanotrophic archaeal group ANME-2 compared to ANME-1, and promote the rapid growth and high diversity of bacterial communities.Our results provide direct evidence of the mechanisms by which deep AOM processes can affect carbon cycling in the deep biosphere and global methane biochemistry.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Microbial Metabolism, State Key Laboratory of Ocean Engineering, Shanghai Jiao Tong University, Shanghai, People's Republic of China; Laboratory of Microbial Ecology and Technology, Ghent University, Gent, Belgium.

ABSTRACT
Numerous studies on marine prokaryotic communities have postulated that a process of anaerobic oxidation of methane (AOM) coupled with sulfate reduction (SR) is the main methane sink in the world's oceans. AOM has also been reported in the deep biosphere. But the responses of the primary microbial players in eliciting changes in geochemical environments, specifically in methane and sulfate supplies, have yet to be fully elucidated. Marine mud volcanoes (MVs) expel a complex fluid mixture of which methane is the primary component, forming an environment in which AOM is a common phenomenon. In this context, we attempted to identify how the prokaryotic community would respond to changes in methane and sulfate intensities, which often occur in MV environments in the form of eruptions, diffusions or seepage. We applied an integrated approach, including (i) biochemical surveys of pore water originated from MV, (ii) in vitro incubation of mud breccia, and (iii) prokaryotic community structure analysis. Two distinct AOM regions were clearly detected. One is related to the sulfate methane transition zone (SMTZ) at depth of 30-55 cm below the sea floor (bsf); the second is at 165-205 cm bsf with ten times higher rates of AOM and SR. This finding contrasts with the sulfide concentrations in pore waters and supports the suggestion that potential AOM activity below the SMTZ might be an important methane sink that is largely ignored or underestimated in oceanic methane budget calculations. Moreover, the incubation conditions below the SMTZ favor the growth of methanotrophic archaeal group ANME-2 compared to ANME-1, and promote the rapid growth and high diversity of bacterial communities. These incubation conditions also promote the increase of richness in bacterial communities. Our results provide direct evidence of the mechanisms by which deep AOM processes can affect carbon cycling in the deep biosphere and global methane biochemistry.

Show MeSH
Related in: MedlinePlus