Quantification of gas bubble emissions from submarine hydrocarbon seeps at the Makran continental margin (offshore Pakistan)

Römer, Miriam; Sahling, Heiko; Pape, Thomas; Bohrmann, Gerhard; Spieß, V.

doi:10.1029/2011jc007424

Cited by 130 publications

(123 citation statements)

References 92 publications

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“…13 The quantity of bubbles and the intensity of seepage on the northern shelf of South Georgia seems to be rather weak in comparison to other seep areas, e.g. Hydrate Ridge 51,52 , the Makran continental margin 12 , Santa Barbara channel 53 , as well as several seepage areas in the Black Sea 54-56 , where vigorous gas bubble emissions and/or strong flares have been documented. However, the large 305 number of emission sites as revealed from our flare imaging, in combination with the strong enrichments in dissolved methane, suggests injection of significant quantities of methane into the bottom water in fjords and the cross-shelf troughs of South Georgia, even though each individual seep may contribute only a small amount of methane.…”

Section: Discussionmentioning

confidence: 99%

“…In contrast to deep-water seep sites, where most bubbles dissolve during ascent through the water column and the dissolved methane is oxidized by microbes [11][12][13] , a fraction of gas emitted from shallow water environments may transgress the sea-atmosphere boundary, especially in storm seasons 14,15 . Therefore, shelf and upper slope areas such as off Spitsbergen 16,17 , in the Black Sea 18 , and off East Siberia 19 are of particular interest when considering the role of methane seepage as a 60 possible contributor to concentrations of methane in the atmosphere.…”

Section: Introductionmentioning

confidence: 99%

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First evidence of widespread active methane seepage in the Southern Ocean, off the sub-Antarctic island of South Georgia

Römer

Torres

Kasten

et al. 2014

Earth and Planetary Science Letters

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25A new extensive submarine cold-seep area was discovered on the northern shelf of South Georgia during R/V Polarstern cruise ANT-XXIX/4 in spring 2013. Hydroacoustic surveys and video-based sea floor observations documented the presence of 133 individual gas bubble emissions, which were restricted to glacially-formed fjords and troughs. Effective methane transport from these emissions into the hydrosphere was proven by relative enrichments of dissolved methane in near-bottom 30 waters. Stable carbon isotopic signatures of the methane pointed to a predominant microbial origin.Although known from many continental margins in the world's oceans, this is the first report of an active area of methane seepage in the Southern Ocean. Our finding of substantial methane emission related to a trough and fjord system, a topographical setting that exists commonly in glaciallyaffected areas, opens up the possibility that methane seepage is a more widespread phenomenon in 35 polar and sub-polar regions than previously thought.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

First evidence of widespread active methane seepage in the Southern Ocean, off the sub-Antarctic island of South Georgia

Römer

Torres

Kasten

et al. 2014

Earth and Planetary Science Letters

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“…According to Table 2, the measured gas fluxes vary from 35 to 368 mLn⋅min −1 . These values are in the range of volumetric fluxes measured in the Central Nile Deep-Sea Fan in the Eastern Mediterranean Sea [76], the Kerch seep area in the northeastern Black Sea [79], and the convergent Makran continental margin [78]. However, these settings are located at much deeper depth than the Aquitaine Shelf.…”

Section: Local Methane Flux From the Nine Gas Streamsmentioning

confidence: 99%

Gas Seepage along the Edge of the Aquitaine Shelf (France): Origin and Local Fluxes

et al. 2017

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During the scientific expedition GAZCOGNE2 at the Bay of Biscay nine gas seeps were sampled for the first time and their flux was measured using an in situ pressure-preservation sampler (PEGAZ, © IFREMER). Overall, three sites were investigated to determine the nature and the origin of the gases bubbling at the seafloor and forming acoustic plumes into the water column, as this was the question raised from the first geologic study of the area. This has guided our study and accordingly corresponds to the main purpose of the present article. Thus, the molecular and isotopic ( D and 13 C) analyses revealed that the gas seeps were primarily composed of methane. Both methane and ethane are of microbial origin, and the former has been generated by microbial reduction of carbon dioxide. Heavier hydrocarbons accounted for less than 0.06% mol of the total amount. Despite the microbial origin of methane, the samples exhibit subtle differences with respect to the 13 C CH 4 values, which varied between −72.7 and −66.1‰. It has been suggested that such a discrepancy was predominantly governed by the occurrence of anaerobic methane oxidation. The PEGAZ sampler also enabled us to estimate the local gas fluxes from the sampled streams. The resulting values are extremely heterogeneous between seeps, ranging from 35 to 368 mLn⋅min −1 . Assuming a steady discharge, the mean calculated methane emission for the nine seeps is of 38 kmol⋅yr −1 . Considering the extent of the seep area, this very local estimate suggests that the Aquitaine Shelf is a very appropriate place to study methane discharge and its fate on continental shelves.

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“…The mats were separated by 0.5-1 m distance from each other ( Fig. 2A), and their distribution reflects sites of active methane seepage (Römer et al, 2012). No benthic metazoans were observed.…”

Section: Seafloor Observationsmentioning

confidence: 99%

Stromatolites below the photic zone in the northern Arabian Sea formed by calcifying chemotrophic microbial mats

Himmler

Smrzka

Zwicker

et al. 2018

Geology

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Chemosynthesis increases alkalinity and facilitates stromatolite growth at methane seeps in 731 m water depth within the oxygen minimum zone (OMZ) in the northern Arabian Sea. Microbial fabrics, including mineralized filament bundles resembling the sulfideoxidizing bacterium Thioploca, mineralized extracellular polymeric substances, and fossilized rod-shaped and filamentous cells, all preserved in 13 C-depleted authigenic carbonate, suggest that biofilm calcification resulted from nitrate-driven sulfide oxidation (ND-SO) and sulfate-driven anaerobic oxidation of methane (SD-AOM). Geochemical batch modeling reveals that the collective effects of ND-SO and SD-AOM increase alkalinity more than SD-AOM alone, explaining the preservation of sulfide-oxidizing bacteria in authigenic carbonate. These findings demonstrate the biogenicity of a conical stromatolite associated with OMZ methane seeps and confirm the fact that, apart from photosynthesis-based metabolisms, chemosynthesis-based metabolisms can also account for stromatolite formation.

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Quantification of gas bubble emissions from submarine hydrocarbon seeps at the Makran continental margin (offshore Pakistan)

Cited by 130 publications

References 92 publications

First evidence of widespread active methane seepage in the Southern Ocean, off the sub-Antarctic island of South Georgia

First evidence of widespread active methane seepage in the Southern Ocean, off the sub-Antarctic island of South Georgia

Gas Seepage along the Edge of the Aquitaine Shelf (France): Origin and Local Fluxes

Stromatolites below the photic zone in the northern Arabian Sea formed by calcifying chemotrophic microbial mats

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