Evidence of methane venting and geochemistry of brines on mud volcanoes of the eastern Mediterranean Sea

Charlou, J. L.; Donval, Jean Pierre; Zitter, T.A.C.; Roy, N; Jean‐Baptiste, Philippe; Foucher, Jean-Paul; Woodside, John

doi:10.1016/s0967-0637(03)00093-1

Cited by 137 publications

(122 citation statements)

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“…However, the Mg/Cl ratio was identical at both sites (0.02) and did not vary with depth, suggesting no net difference in Mg 2+ sources/sinks between the sites. The slight decrease in Mg 2+ concentration over depth observed at both sites may result from dolomite or low-magnesium calcite precipitation (Charlou et al, 2003). The DIC concentrations observed in both brines were much lower than those (>10 mM) observed in nearby sediments (Joye et al, 2004;Orcutt et al, 2005) and may have resulted from DIC removal via carbonate precipitation, particularly at the GC233 site.…”

Section: Geochemical Signatures Of Deep-sea Brinesmentioning

confidence: 77%

“…The gas plume rising from the mud volcano as visualized using CHIRP sonar (data not shown) reached >200 m above the seafloor (Joye et al, unpublished data) whereas the sparse bubble stream at GC233 was not visible in CHIRP traces (De Beukelaer et al, 2003). Methane-rich plumes originating from cold seeps, such as those documented in the Gulf of Mexico (Aharon et al, 1992a;MacDonald et al, 2000;MacDonald et al, 2002) are common features along continental margins across the globe (Charlou et al, 2003 and references therein). Seafloor mud volcanoes, in particular, are likely important, but poorly constrained, sources of methane to the overlying water column and potentially to the atmosphere (Milkov, 2000;Dimitrov, 2002).…”

Section: Geochemical Signatures Of Deep-sea Brinesmentioning

confidence: 99%

“…Brine-filled basins with diameters of several kilometers and depths of hundreds of meters are known from the Mediterranean Sea (Cita, 1990;Cita et al, 1989;De Lange and Brumsack, 1998;MEDINAUT/MEDINETH, 2000) and the outer continental slope of the Gulf of Mexico (Sheu, 1990;Bouma and Bryant, 1994;MacDonald et al, 1990;Neurauter and Bryant, 1990;Neurauter and Roberts, 1994;Shokes et al, 1977). Geochemical profiles through the seawater-brine interface in these basins show 296 S. B.…”

Section: Introductionmentioning

confidence: 99%

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Geophysical and geochemical signatures of Gulf of Mexico seafloor brines

et al. 2005

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Abstract. Geophysical, temperature, and discrete depthstratified geochemical data illustrate differences between an actively venting mud volcano and a relatively quiescent brine pool in the Gulf of Mexico along the continental slope. Geophysical data, including laser-line scan mosaics and subbottom profiles, document the dynamic nature of both environments. Temperature profiles, obtained by lowering a CTD into the brine fluid, show that the venting brine was at least 10 • C warmer than the bottom water. At the brine pool, thermal stratification was observed and only small differences in stratification were documented between three sampling times (1991, 1997 and 1998). In contrast, at the mud volcano, substantial temperature variability was observed, with the core brine temperature being slightly higher than bottom water (by 2 • C) in 1997 but substantially higher than bottom water (by 19 • C) in 1998. Detailed geochemical samples were obtained in 2002 using a device called the "brine trapper" and concentrations of dissolved gases, major ions and nutrients were determined. Both brines contained about four times as much salt as seawater and steep concentration gradients of dissolved ions and nutrients versus brine depth were apparent. Differences in the concentrations of calcium, magnesium and potassium between the two brine fluids suggest that the fluids are derived from different sources, have different dilution/mixing histories, or that brine-sediment reactions are more important at the mud volcano. Substantial concentrations of methane, ammonium, and silicate were observed in both brines, suggesting that fluids expelled from deep ocean brines are important sources of these constituents to the surrounding environment.

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Section: Geochemical Signatures Of Deep-sea Brinesmentioning

confidence: 77%

Section: Geochemical Signatures Of Deep-sea Brinesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Geophysical and geochemical signatures of Gulf of Mexico seafloor brines

et al. 2005

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“…DHABs are far below the photic zone (3,,600 m deep) and contain brines, the origin of which has been attributed to dissolution of 5.9-to 5.3-million-year-old Messinian evaporites (1). Urania is less saline than the other Mediterranean DHABs, with NaCl concentrations 5.4-7 times higher than normal seawater, but has higher concentrations of methane (5.56 mM) and exceptionally high levels of sulfide (up to 16 mM), making Urania basin among the most sulfidic marine water bodies on Earth (2)(3)(4).…”

mentioning

confidence: 99%

Sulfur cycling and methanogenesis primarily drive microbial colonization of the highly sulfidic Urania deep hypersaline basin

Borin

Brusetti

Mapelli

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

116

155

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Urania basin in the deep Mediterranean Sea houses a lake that is >100 m deep, devoid of oxygen, 6 times more saline than seawater, and has very high levels of methane and particularly sulfide (up to 16 mM), making it among the most sulfidic water bodies on Earth. Along the depth profile there are 2 chemoclines, a steep one with the overlying oxic seawater, and another between anoxic brines of different density, where gradients of salinity, electron donors and acceptors occur. To identify and differentiate the microbes and processes contributing to the turnover of organic matter and sulfide along the water column, these chemoclines were sampled at a high resolution. Bacterial cell numbers increased up to a hundredfold in the chemoclines as a consequence of elevated nutrient availability, with higher numbers in the upper interface where redox gradient was steeper. Bacterial and archaeal communities, analyzed by DNA fingerprinting, 16S rRNA gene libraries, activity measurements, and cultivation, were highly stratified and metabolically more active along the chemoclines compared with seawater or the uniformly hypersaline brines. Detailed analysis of 16S rRNA gene sequences revealed that in both chemoclines ␦-and -Proteobacteria, predominantly sulfate reducers and sulfur oxidizers, respectively, were the dominant bacteria. In the deepest layers of the basin MSBL1, putatively responsible for methanogenesis, dominated among archaea. The data suggest that the complex microbial community is adapted to the basin's extreme chemistry, and the elevated biomass is driven largely by sulfur cycling and methanogenesis.deep anoxic hypersaline lake ͉ element cycling ͉ geosphere-biosphere interaction ͉ Mediterranean Sea ͉ microbial diversity T he Urania basin is one of the deep-sea hypersaline anoxic basins (DHABs) located in the eastern Mediterranean Sea. DHABs are far below the photic zone (3,200-3,600 m deep) and contain brines, the origin of which has been attributed to dissolution of 5.9-to 5.3-million-year-old Messinian evaporites (1). Urania is less saline than the other Mediterranean DHABs, with NaCl concentrations 5.4-7 times higher than normal seawater, but has higher concentrations of methane (5.56 mM) and exceptionally high levels of sulfide (up to 16 mM), making Urania basin among the most sulfidic marine water bodies on Earth (2-4).Interfaces are considered to be hot spots for biological activity (2, 5), and environmental gradients represent an important part of the biosphere that must be accounted for in models of global biogeochemical cycles, especially in otherwise oligotrophic environments like the Eastern Mediterranean (6).In the present study, we discovered 2 different environmental chemoclines within the Urania basin. We finely dissected the gradients and compared the oxic/anoxic upper interface of Urania basin with those found in chemically different DHABs. We concluded that the lower overall salinity but higher sulfide and methane concentrations in Urania DHAB are the primary factors determining the observed ...

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“…26 Solid crystallines made of methane surrounded by water molecules, called "methane hydrates," are in certain instances associated with cold seeps. 27 These crystallines have a strong potential as a source of energy and, if utilized, would constitute a positive greenhouse gas. 28 Because methane is a powerful greenhouse gas, there is evidence that gas hydrates constitute a methane buffer and therefore a buffer to the greenhouse effect.…”

Section: Cold Seeps and Other Similar Deep Sea Ecosystemsmentioning

confidence: 99%

Bioprospecting of genetic resources in the deep seabed; Scientific, legal, and policy aspects

2005

Industrial Biotechnology

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Evidence of methane venting and geochemistry of brines on mud volcanoes of the eastern Mediterranean Sea

Cited by 137 publications

References 50 publications

Geophysical and geochemical signatures of Gulf of Mexico seafloor brines

Geophysical and geochemical signatures of Gulf of Mexico seafloor brines

Sulfur cycling and methanogenesis primarily drive microbial colonization of the highly sulfidic Urania deep hypersaline basin

Bioprospecting of genetic resources in the deep seabed; Scientific, legal, and policy aspects

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