Changes in the microbial communities associated with Gorgonia ventalina during aspergillosis infection

The surface mucopolysaccharide layer (SML) secreted by corals is a rich environment where bacteria live and proliferate, with population levels often being several orders of magnitude higher than in the surrounding waters (at least for culturable microbes). Some studies have suggested that these communities play an important role in energy and nutrient flux in marine environments. We hypothesize that the microbial community structure of the SML also plays a role in protection against disease. This hypothesis is based on studies that have shown differences in the bacterial composition of the mucus of healthy and diseased corals. In this study we tested the differences in the microbial communities living in association with the SML of healthy and diseased Gorgonia ventalina by comparing their metabolic profiles using Biolog EcoPlates. Overall, metabolic profiles of the coral surface microbiota were significantly different to those in the water column based on stepwise canonical discriminant analyses (CDAs). Furthermore, differences between communities living in healthy and diseased corals were also found. Changes were observed between affected and unaffected areas of the same colony, although these changes were not as obvious as between individual healthy and diseased colonies. Results suggest that the microbial communities living in the SML of G. ventalina are affected by the presence of aspergillosis, even if the area is not in direct contact with the infection. This suggests the possibility of changes in the composition of the SML throughout the colony as a response to aspergillosis infection.