Response of an archaeal community from anoxic coastal marine sediments to experimental petroleum contamination
Résumé
To achieve a better understanding of the ecological significance of Archaea in relation to petroleum contamination, we examined the composition of archaeal communities in anoxic coastal marine infralittoral sediments and their response to simulated petroleum contamination. Sediments were collected at an experimental site, and half were mixed with oil. Control and oiled sediments were then reworked into PVC cores that were inserted into the sediment at their sampling site at 20 m water depth. After 503 d of in situ incubation, molecular and statistical analyses clearly showed that petroleum contamination induced significant shifts in the composition of archaeal communities inhabiting these anoxic sediments. Overall, contamination led to a significant decrease in diversity. Control sediments were dominated by Crenarchaeota, whereas in oiled sediments,Euryarchaeota became dominant, as attested by the particular contribution of Methanococcoides, Methanosarcina, and Methanolobus sequences. Methanogens could be indirectly related to the degradation of the added hydrocarbons by participating in syntrophic consortia with hydrocarbon-degrading acetogenic bacteria. In addition, the abundance of anaerobic methane-oxidizing Archaea sequences in oiled sediments could indicate that anaerobic oxidation of methane (AOM) occurs at the depth selected for the analyses. Further studies undertaken to quantify vertical distribution of AOM, methanogenic activity, and their potential causative Archaea would help to enhance understanding of this complex petroleum-contaminated sedimentary system.
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