On the reefs of Bermuda, the coral Diploria labyrinthiformis is rarely infected with black band disease (BBD) while BBD-infected colonies of D. strigosa are common. This study investigated several possible explanations for the documented difference in BBD prevalence including: 1) temperature and light conditions differentially affect the progression of the disease among these two species; 2) the bacterial communities associated with each species are different and 3) the bacterial composition of BBD in Bermuda is unique from that of other geographical regions where D. labyrinthiformis has been reported with BBD. Results suggest that light and temperature are important variables in determining BBD progression for both species; reef location, rather than coral species dictates the coral associated bacterial diversity; and the BBD bacterial mat in Bermuda is unique compared to other regions of the Caribbean. Many factors are likely responsible for the low occurrence of BBD among D. labyrinthiformis in Bermuda.

Disease and bleaching are two conditions which commonly lead to coral death. Among coral species, susceptibility to disease and bleaching is variable, and Pseudodiploria strigosa tends to be diseased more than Diploria labyrinthiformis, while D. labyrinthiformis bleaches more readily. The focus of this dissertation was to investigate and compare multiple components of these two coral species, and identify how they may relate to disease and bleaching resistance. Compenetnts examined included the surface mucopolysacharide layer (SML) thickness, gene expression, microbial associates, and a white plague aquarium study. The SML thickness decresased with increasing temperature regardless of coral species, indicating that SML thickness does not likely play a role in differences between susceptablities of these two coral species. However, Diploria labyrinthiformis had a lower mortality rate at 31°C, had fewer differentially expressed genes assossiated with stress, and upregulated genes associated with innate immunity in the summer, all of which may contribute to its relative disease resistance. The bacterial associates of each coral species were also monitored. Differences between the two coral species were primarily caused by Clostridia, Gammaproteobacteria, and rare species which may contribute to the relatively higher disease susceptibility of P. strigosa. Lastly, an aquarium study suggested that a potential pathogen of the Roseobacter clade infects both D. labyrinthiformis and P. strigosa, and might be transmitted by the Cryptochiridae gall crab, indicating that potential disease vectors associated with these two coral species may also play a role in disease resistance and resilience.

Knowledge of effective reef restoration techniques are necessary in this age of worldwide coral reef decline. Coral transplantation is a restoration technique employed after natural (i.e. hurricanes) and anthropogenic (i.e. vessel groundings) physical disturbance events. The study was conducted to compare the efficacy of propagating small colony fragments in laboratory and field conditions in terms of survival and growth. Fragment growth and survival were assessed for six scleractinian boulder corals common to Florida and Caribbean reefs: Montastraea annularis, M. cavernosa, Diploria clivosa, Siderastrea siderea, S. radians and Dichocoenia stokesii. Broken coral colonies were salvaged from vessel grounding sites and marine debris, fragmented into pucks and secured to travertine tiles. One hundred and fifty-three coral colony fragments were cultivated in an ex situ laboratory nursery and 133 coral colony fragments were cultivated in an in situ field nursery and monitored for 13 months. Survival of all colonies was 94%, with 98% survival in the laboratory treatment and 89% survival in the field treatment. Complete colony mortality was documented in three S. radians colonies, all in the laboratory treatment. All colony loss in the field treatment was due to colony pucks being detached from the tiles. Overall mean percent change in colony tissue area from initial to final monitoring events was calculated to determine growth. Across species, growth was greater in the laboratory treatment (76 ± 4 % SEM) in comparison to the field treatment (27 ± 5 % SEM). Positive growth was observed in D. clivosa, D. stokesii, M. annularis, M. cavernosa and S. siderea in the laboratory treatment. In the field treatment, D. clivosa, M. annularis and M. cavernosa were the only species that exhibited positive growth. Negative growth was observed in both the laboratory and field treatments for S. radians. In conclusion, colonies propagated in the ex situ nursery (laboratory treatment) had higher growth and survival than colonies propagated in the in situ nursery (field treatment). A critical acclimation period accomplished through the use of stable laboratory conditions will produce healthier, more secure coral colonies that may be used to repopulate disturbed reef sites.