Éditeur(s) : Nature
Résumé : Mud volcanism is an important natural source of the greenhouse gas methane to the hydrosphere and atmosphere(1,2). Recent investigations show that the number of active submarine mud volcanoes might be much higher than anticipated ( for example, see refs 3 - 5), and that gas emitted from deep-sea seeps might reach the upper mixed ocean(6-8). Unfortunately, global methane emission from active submarine mud volcanoes cannot be quantified because their number and gas release are unknown(9). It is also unclear how efficiently methane-oxidizing microorganisms remove methane. Here we investigate the methane-emitting Haakon Mosby Mud Volcano (HMMV, Barents Sea, 72 degrees N, 14 degrees 44' E; 1,250 m water depth) to provide quantitative estimates of the in situ composition, distribution and activity of methanotrophs in relation to gas emission. The HMMV hosts three key communities: aerobic methanotrophic bacteria (Methylococcales), anaerobic methanotrophic archaea (ANME-2) thriving below siboglinid tubeworms, and a previously undescribed clade of archaea (ANME-3) associated with bacterial mats. We found that the upward flow of sulphate- and oxygen-free mud volcano fluids restricts the availability of these electron acceptors for methane oxidation, and hence the habitat range of methanotrophs. This mechanism limits the capacity of the microbial methane filter at active marine mud volcanoes to <40% of the total flux.
Nature (depuis 1997) (0028-0836) (Nature), 2006-10 , Vol. 443 , N. 7113 , P. 854-858

Droits : 2006 Nature Publishing Group
http://archimer.ifremer.fr/doc/2006/publication-4514.pdf
DOI:10.1038/nature05227
http://archimer.ifremer.fr/doc/00000/4514/

Éditeur(s) : Springer
Résumé : Two highly active mud volcanoes located in 990-1,265 m water depths were mapped on the northern Egyptian continental slope during the BIONIL expedition of R/V Meteor in October 2006. High-resolution swath bathymetry and backscatter imagery were acquired with an autonomous underwater vehicle (AUV)-mounted multibeam echosounder, operating at a frequency of 200 kHz. Data allowed for the construction of similar to 1 m pixel bathymetry and backscatter maps. The newly produced maps provide details of the seabed morphology and texture, and insights into the formation of the two mud volcanoes. They also contain key indicators on the distribution of seepage and its tectonic control. The acquisition of high-resolution seafloor bathymetry and acoustic imagery maps with an AUV-mounted multibeam echosounder fills the gap in spatial scale between conventional multibeam data collected from a surface vessel and in situ video observations made from a manned submersible or a remotely operating vehicle.
Marine Geophysical Researches (0025-3235) (Springer), 2008-12 , Vol. 29 , N. 4 , P. 275-290

Droits : 2008 Springer. Part of Springer Science+Business Media
http://archimer.ifremer.fr/doc/2008/publication-6395.pdf
DOI:10.1007/s11001-009-9063-3
http://archimer.ifremer.fr/doc/00000/6395/