Bacterial communities inhabiting the healthy tissues of two Caribbean reef corals: interspecific and spatial variation

Bacterial communities inhabiting healthy tissues of the reef-building corals Diploria strigosa and Montastraea annularis were evaluated across a human-induced environmental gradient along the southern coast of Curacao, Netherlands Antilles. Variations in bacterial communities inhabiting coral tissues were determined using terminal restriction fragment length polymorphisms (T-RFLP) of 16S rRNA genes, and the delta(15)N value of coral tissue was used to assess the relative amount of human contaminants at each reef locality. Bacterial communities of D. strigosa were more variable than M. annularis, but there were no systematic differences in the populations of healthy M. annularis and D. strigosa. The delta(15)N value of coral tissues showed as much as a 1.5 parts per thousand increase in the impacted versus the non-impacted localities. While M. annularis showed no significant variation in bacterial community structure due to local reef conditions, the bacterial communities of D. strigosa showed dramatic shifts in community structure. The most abundant bacterial taxa inhabiting D. strigosa display increased dominance at impacted localities. By linking variations in microbial communities with an understanding of variations in local environmental conditions, this study provides a means of assessing potential factors that may impact the microbial habitat of coral tissues as well as overall reef health.