Bacteria associated with the Mediterreanean gorgonian Paramuricea clavata: a spatio-temporal characterization
Résumé
In Nortwestern Mediterranean Sea, recurrent mass mortalities have been observed affecting benthic macroinvertebrate species during climatic anomalies in summer. One of the most affected species was the red gorgonian Paramuricea clavata, and the infectious pathogen Vibrio coralliilyticus was implicated in disease in this organism. As the composition and dynamics of the natural microbial communities living in association with temperate Mediterranean gorgonians are unknown, we attempted to establish a baseline for diversity and abundance of the bacterial community of P. clavata. In this study, we used both terminal-restriction fragment length polymorphism (T-RFLP) and clone library analysis to assess the spatio-temporal changes of bacterial assemblages associated with the gorgonian. We found a clear difference between the bacterial communities during summer and winter, while T-RFLP profiles were highly similar between P. clavata populations separated by hundreds of kilometers. Sequencing data from 16S rDNA clone libraries demonstrated the presence of distinct phylogenetic taxa during summer and winter, with an increased diversity in warm season. Monitoring of bacterial assemblage variability during a longer period of time is currently in process to assess if the seasonal pattern observed between summer and winter is repeated during successive years. In the context of recurrent gorgonian diseases and mortalities, this picture of the bacterial communities structure will be helpful to monitor the effects of thermal anomalies on the resident microbial flora.