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16/06 Séminaires Généraux: Daniel Birgel (Université de Vienne)

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Aerobic methanotrophs in ancient marine methane seep carbonates: a comparison with contemporaneous representatives.

 

Methane is among the most severe greenhouse gases on our planet. Catastrophic methane releases both on land and in marine sites led to strong climate perturbations in the past. Today, highest methane production occurs in wetlands, accounting for about 40% of the total methane emissions. In the marine realm, methane emissions make up 10-20% of the total emissions.  Under modern climate conditions it is believed that 90% of the methane produced in aquatic environments is oxidized before it reaches the atmosphere. Usually, in marine environments, methane is thought to be oxidized in anoxic sediments by anaerobic methanotrophs (a consortium of archaea and sulphate-reducing bacteria). However, it has been recently demonstrated that aerobic methane oxidation in the marine water column is also an important process, preventing more severe methane emissions to the atmosphere. Interestingly, aerobic methanotrophic bacteria also occur in marine methane seeps, whereas the overall environmental conditions are rather anoxic.

An overview will be given about the occurrence and possible role of aerobic methanotrophic bacteria in marine methane seep deposits. The lipids (hopanoids and steroids) produced by these microorganisms are very persistent biomarkers, which can be traced as well in ancient sediments and rocks as ‘molecular fossils’.  However, such micro-organisms are only poorly studied for their cellular lipid inventory. We thus just started to culture halotolerant aerobic methanotrophic bacteria which are adapted to live at methane seeps. One of the goals is to compare the lipid biomarker signatures of the cultured bacteria with those found in the environment. So far, marine aerobic methanotrophic bacteria were thought to thrive predominantly in the water column, but possibly they also seem to be active in otherwise anoxic, sedimentary environments.


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Vincent Grossi

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Département ENS
  • Directeur :
    Stéphane Labrosse
  • Secrétaire :
    Emmanuelle Lousson
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