Lesion recovery and the bacterial microbiome in two Caribbean gorgonian corals
In the Caribbean, gorgonian corals dominate many coral reefs, while scleractinian coral cover has declined. Gorgonian corals deal with stressors such as lesions caused by wave action, predation, or human activities. In June 2012, artificial wounds were inflicted on branches of the gorgonians Eunicea flexuosa and Pseudoplexaura porosa found at 3 5 m depth on a patch reef (20deg52'5.23''N, 86deg51'58.92''W) near Puerto Morelos, Mexico. Following healing, injured and uninjured branches were collected to determine the effect of lesions on gorgonian biochemistry, symbiosis, microbiome, and immune response. Lesion recovery in E. flexuosa took twice as long as in P. porosa. In both species, tissues at and surrounding the lesions contained significantly higher sclerite content per dry weight but lower protein per surface area. In and around the lesion area, the density of symbiotic dinoflagellates, Symbiodinium spp. was lower than in uninjured branches, although Symbiodinium photochemical efficiency in tissues surrounding the lesion was not affected. The gorgonian species differed in their bacterial microbiome, but the overall bacterial community and dominant bacterial taxa did not differ between injured and uninjured branches, although the prevalence of some less common bacterial groups did vary. The two species exhibited distinct immune responses, whereby different components of the melanization cascade were activated, and exochitinase was mobilized only in E. flexuosa. While the gorgonian species differed in their lesion recovery response, both healed without signs of disease or colonization by fouling organisms. The capacity to recover successfully from injuries may partly explain why gorgonian corals dominate Caribbean coral reefs.