The endemic Mediterranean zooxanthellate reef-builder Cladocora caespitosa is among the organisms most affected by warming-related mass mortality events in the Mediterranean Sea.

Taking into account that corals contain a diverse microbiota that plays a key role in their health, this paper examines for the first time the microbiome and pathobiome* associated with C. caespitosa in three Western Mediterranean locations (Genova, Columbretes islands and Tabarca island).

The obtained results show that the microbial communities associated with this coral showed biogeographical differences, but showed a common core microbiome that, as the authors suggest, probably plays a key role in the coral holobiont.

The study shows that the putatively pathogenic microbial assemblage (pathobiome) of C. caespitosa also seemed to depend on geographic location and human footprint. It was found that in locations near the coast and with higher human influence (i.e. Genova and Tabarca island), the pathobiome was entirely constituted by Vibrio species. However, in the Columbretes islands, located off the coast and the most pristine of the analysed locations, no changes among microbial communities associated to healthy and warming-impacted samples were detected.

The authors conclude that the results of the study provide new insights into the microbiome of temperate corals and its role in coral health status, highlighting its dependence on the local environmental conditions and the human footprint.

*the consortium of microbes within the microbiome that play a direct role in the causation of disease.

Rubio-Portillo E, Kersting DK, Linares C, Ramos-Esplá AA, Antón J (2018) Biogeographic differences in the microbiome and pathobiome of the coral Cladocora caespitosa in the Western Mediterranean Sea. Frontiers in Microbiology 9:22