Les associations bacteries-matiere particulaire en milieu pelagique cotier: Exemples de variations spatiales et temporelles

Studies concerning the respective role of free-living and particle-bound bacteria in pelagic ecosystems, sometimes gave opposite results. The comparative distribution of these bacterial patterns was studied in two sites of Brittany. In the Bay of Brest, a shallow and semi-enclosed area, the bacterial communities were dominated by the free-living forms, except during the phytoplankton bloom, which was accompanied by a clear increase of the particle-bound forms. Off the west coasts of Brittany, the Ushant front separates stratified water masses from mixed water masses. The distribution of particle-bound bacteria fluctuated according to the structure of the water masses and in mixed waters, was related to particulate matter from different origins. Results indicate that a previous knowledge of the distribution of bacterial patterns was necessary before the study of the role of the different components of the bacterial communities.