The impact of long-term hydrocarbon exposure on the structure, activity, and biogeochemical functioning of microbial mats Aubé, J. Senin, P. /Pringault, Olivier Bonin, P. Deflandre, B. Bouchez, O. Bru, N. Biritxinaga-Etchart, E. Klopp, C. Guyoneaud, R. Goni-Urriza, M. Biogeochemical functioning Diversity Hydrocarbonoclastic bacteria Microbial mats Photosynthetic microbial mats are metabolically structured systems driven by solar light. They are ubiquitous and can grow in hydrocarbon-polluted sites, Our aim is to determine the impact of chronic hydrocarbon contamination on the structure, activity, and functioning of a microbial mat. We compared it to an uncontaminated mat harboring similar geochemical characteristics. The mats were sampled in spring and fall for 2 years. Seasonal variations were observed for the reference mat: sulfur cycle-related bacteria dominated spring samples, while Cyanobacteria dominated in autumn. The contaminated mat showed minor seasonal variation; a progressive increase of Cyanobacteria was noticed, indicating a perturbation of the classical seasonal behavior. Hydrocarbon content was the main factor explaining the differences in the microbial community structure; however, hydrocarbonoclastic bacteria were among rare or transient Operational Taxonomic Units (OTUs) in the contaminated mat We suggest that in long-term contaminated systems, hydrocarbonoclastic bacteria cannot be considered a sentinel of contamination. 2016 text https://www.documentation.ird.fr/hor/fdi:010068229 fdi:010068229 Aubé J., Senin P., Pringault Olivier, Bonin P., Deflandre B., Bouchez O., Bru N., Biritxinaga-Etchart E., Klopp C., Guyoneaud R., Goni-Urriza M.. The impact of long-term hydrocarbon exposure on the structure, activity, and biogeochemical functioning of microbial mats. 2016, 111 (1-2), 115-125 EN FRANCE MEDITERRANNEE BERRE ETANG