Terrestrial methane seeps and mud volcanoes: A global perspective of gas origin

Etiope, Giuseppe; Feyzullayev, A. A.; Baciu, Călin

doi:10.1016/j.marpetgeo.2008.03.001

Cited by 181 publications

(168 citation statements)

References 30 publications

(41 reference statements)

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“…But seepage of microbial geological (fossil) methane, which is C 2 -C 6 free and isotopically indistinguishable from modern biologic CH 4 , cannot be excluded. Such a microbial seepage, releasing CH 4 with δ 13 C o − 60‰ is in fact quite common in the Transylvanian Basin (Etiope et al, 2009;Spulber et al, 2010;Ionescu, 2015). In this respect, radiocarbon analyses of CH 4 would be necessary to reveal a possible geological component of CH 4 in the lakes.…”

Section: Water Chemistrymentioning

confidence: 99%

Contrasting taxonomic stratification of microbial communities in two hypersaline meromictic lakes

et al. 2015

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Hypersaline meromictic lakes are extreme environments in which water stratification is associated with powerful physicochemical gradients and high salt concentrations. Furthermore, their physical stability coupled with vertical water column partitioning makes them important research model systems in microbial niche differentiation and biogeochemical cycling. Here, we compare the prokaryotic assemblages from Ursu and Fara Fund hypersaline meromictic lakes (Transylvanian Basin, Romania) in relation to their limnological factors and infer their role in elemental cycling by matching taxa to known taxon-specific biogeochemical functions. To assess the composition and structure of prokaryotic communities and the environmental factors that structure them, deepcoverage small subunit (SSU) ribosomal RNA (rDNA) amplicon sequencing, community domainspecific quantitative PCR and physicochemical analyses were performed on samples collected along depth profiles. The analyses showed that the lakes harbored multiple and diverse prokaryotic communities whose distribution mirrored the water stratification patterns. Ursu Lake was found to be dominated by Bacteria and to have a greater prokaryotic diversity than Fara Fund Lake that harbored an increased cell density and was populated mostly by Archaea within oxic strata. In spite of their contrasting diversity, the microbial populations indigenous to each lake pointed to similar physiological functions within carbon degradation and sulfate reduction. Furthermore, the taxonomy results coupled with methane detection and its stable C isotope composition indicated the presence of a yet-undescribed methanogenic group in the lakes' hypersaline monimolimnion. In addition, ultrasmall uncultivated archaeal lineages were detected in the chemocline of Fara Fund Lake, where the recently proposed Nanohaloarchaeota phylum was found to thrive.

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Section: Water Chemistrymentioning

confidence: 99%

Contrasting taxonomic stratification of microbial communities in two hypersaline meromictic lakes

et al. 2015

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“…Stable isotopic and molecular compositions of hydrocarbons have been broadly utilized to identify the hydrocarbon origin and to trace the hydrocarbon migration (Whiticar, 1990;Etiope et al, 2009;Sun et al, 2010). On the basis of d 13 C-CH 4 and d 2 H-CH 4 values, about 25% out of 143 studied MVs around the world release microbial methane or a mixture of microbial and thermogenic methane (Etiope et al, 2009).…”

Section: Introductionmentioning

confidence: 99%

“…On the basis of d 13 C-CH 4 and d 2 H-CH 4 values, about 25% out of 143 studied MVs around the world release microbial methane or a mixture of microbial and thermogenic methane (Etiope et al, 2009). In contrast, a plot of the same data set on the d 13 C-CH 4 versus C 1 /(C 2 þ C 3 ) diagram shows that most terrestrial MVs produce gas signals falling within an ambiguous sector due to post-genetic processes, such as microbial oxidation, mixing or molecular fractionation during migration (Etiope et al, 2009). This contradictory interpretation illustrates the complexity in the identification of gas origin, as well as strengthens the importance of the post-formational microbial process at shallow depths.…”

Section: Introductionmentioning

confidence: 99%

Metabolic stratification driven by surface and subsurface interactions in a terrestrial mud volcano

et al. 2012

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Terrestrial mud volcanism represents the prominent surface geological feature, where fluids and hydrocarbons are discharged along deeply rooted structures in tectonically active regimes. Terrestrial mud volcanoes (MVs) directly emit the major gas phase, methane, into the atmosphere, making them important sources of greenhouse gases over geological time. Quantification of methane emission would require detailed insights into the capacity and efficiency of microbial metabolisms either consuming or producing methane in the subsurface, and establishment of the linkage between these methane-related metabolisms and other microbial or abiotic processes. Here we conducted geochemical, microbiological and genetic analyses of sediments, gases, and pore and surface fluids to characterize fluid processes, community assemblages, functions and activities in a methane-emitting MV of southwestern Taiwan. Multiple lines of evidence suggest that aerobic/anaerobic methane oxidation, sulfate reduction and methanogenesis are active and compartmentalized into discrete, stratified niches, resembling those in marine settings. Surface evaporation and oxidation of sulfide minerals are required to account for the enhanced levels of sulfate that fuels subsurface sulfate reduction and anaerobic methanotrophy. Methane flux generated by in situ methanogenesis appears to alter the isotopic compositions and abundances of thermogenic methane migrating from deep sources, and to exceed the capacity of microbial consumption. This metabolic stratification is sustained by chemical disequilibria induced by the mixing between upward, anoxic, methane-rich fluids and downward, oxic, sulfate-rich fluids.

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“…Petroleum biodegradation process is a phenomenon that was neglected in the past, but today it is considered to affect a large fraction of conventional oil reserves (Dimitrakopoulos and Muehlenbachs, 1987;Head et al, 2003;Jones et al, 2007). Such a biodegradation typically modifies also propane and other nalkanes isotopic values, leading to large isotopic separations between successive n-alkanes and high C2/C3 and/ or iC4/nC4 ratios (Etiope et al, 2009a;Etiope et al, 2009b;Waseda and Iwano, 2008). Therefore, the isotopic and molecular compositions of the gas bubbles and the hydrate bound-gases show that they meet the requirements of seeps which have undergone a biodegradation at the reservoir level along with a secondary methanogenesis (Etiope et al, 2009b).…”

Section: Wwwintechopencommentioning

confidence: 99%

Geochemical Dynamics of the Natural-Gas Hydrate System in the Sea of Marmara, Offshore Turkey

Ruffine¹,

Fandiño²,

Étoubleau³

et al. 2012

Advances in Natural Gas Technology

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Terrestrial methane seeps and mud volcanoes: A global perspective of gas origin

Cited by 181 publications

References 30 publications

Contrasting taxonomic stratification of microbial communities in two hypersaline meromictic lakes

Contrasting taxonomic stratification of microbial communities in two hypersaline meromictic lakes

Metabolic stratification driven by surface and subsurface interactions in a terrestrial mud volcano

Geochemical Dynamics of the Natural-Gas Hydrate System in the Sea of Marmara, Offshore Turkey

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