Differential distribution of octocorals and scleractinians around St. John and St. Thomas, US Virgin Islands

While the decline in cover of scleractinian corals on Caribbean reefs is well known, little attention has been paid to other taxa that might covary in abundance. This study focused on octocorals around St. John and St. Thomas, US Virgin Islands, in order to: (1) describe variation in octocoral communities, (2) test for similarity in distribution of octocorals and scleractinians, and (3) identify factors associated with the distribution of octocorals that have value in understanding how reefs will change in the future. Photoquadrats recorded in 2011 on north and south shores were used to quantify octocoral and scleractinian abundance with generic resolution. MDS and PERMANOVA revealed clearer community variation relative to the spatial scales of investigation for octocorals compared to scleractinians. Multivariate spatial structuring for octocorals differed from that of scleractinians, suggesting the taxa responded in dissimilar ways to the environmental conditions. PCO supported the differences in the structuring of community types and revealed the roles of octocorals (Eunicea, Briareum, Plexaurella, Muriceopsis, Pterogorgia, and Muricea) in distinguishing among islands, shores, and sites; scleractinians (Porites, Colpophyllia, Siderastrea, and Orbicella) distinguished sites. These results suggest that changes in the community structure of Caribbean reefs favoring octocorals may promote local-scale provincialization.