Human activities have substantially increased the atmospheric concentrations of greenhouse gases, resulting in warmer ocean temperatures that are having a negative impact on reef corals, which are highly susceptible to changes in temperature. Understanding the degree to which species vary in their tolerance to elevated temperatures and whether this variation is heritable is important in determining their ability to adapt to climate change. In order to address this, Acropora cervicornis fragments from 20 genetically distinct colonies were kept at either ambient or elevated temperatures, and mortality was monitored for 26 days. Heritability of thermal tolerance was estimated using a clonal method comparing the difference in lifespan within and among clones in a one-way ANOVA, as well as a marker based method using the program MARK (Ritland 1996) to estimate relatedness between colonies. To understand the physiological basis of thermal tolerance, tissue samples from both treatments were taken after 12 hours to investigate gene expression associated with sub-lethal temperature stress at both the mRNA and the protein level. The results revealed that this population of A. cervicornis has a relatively high amount of total genetic variation in thermal tolerance (H2 = 0.528), but low additive genetic variation for this trait (h2 = 0.032). In addition, both gene expression and protein expression among colonies were highly variable and did not show consistent patterns related to differences in thermal tolerance among colonies. These results reveal that this population of A. cervicornis may have a limited capacity to respond to projected increases in ocean temperatures. In addition, the results suggest that the molecular basis of thermal tolerance in this species is complex and that there are potentially many genotypic combinations that can result in a heat-tolerant phenotype.

Coral nurseries have become a popular and successful method to produce coral fragments for reef-restocking and restoration projects worldwide. Numerous in-situ coral nurseries have been established and many studies have focused on the most effective way to produce coral fragments in offshore nurseries. In contrast, production of coral fragments in land-based nurseries is rarely studied despite a growing knowledge of coral husbandry and coral aquaculture. Little data exist on the success of tank-raised corals when transplanted back into reef environments. This thesis presents the results of a study designed to assess the use of land-based coral nurseries in production of fragments of the Atlantic staghorn coral Acropora cervicornis for the purposes of reef re-stocking and restoration. The first objective of the study was to assess if A. cervicornis fragments can be produced in aquarium conditions at comparable rates to offshore nurseries. Fragments from the same wild donor colonies were placed in an offshore nursery and a land-based nursery and monitored for survival, growth, branch production, and branch thickness for 16 months. Survival was lower in the land-based nursery, largely due to a mechanical failure. Linear extension was lower in the land-based nursery until nursery conditions were evaluated and optimized. The optimization process included changes to water quality, temperature control, and lighting. Post-optimization, linear extension in the land-based nursery exceeded the offshore nursery, with a maximum monthly growth rate of 16.0 ± 5.3 mm month-1. The maximum monthly rate in the offshore nursery was 10.6 ± 4.1 mm month-1. Branch number and thickness were also lower initially in the land-based nursery, however both metrics increased rapidly after optimization. This experiment shows that A. cervicornis can be successfully grown in a land-based nursery, and that linear extension and fragment production can be higher than in offshore nurseries if environmental conditions are maintained within optimum ranges. This experiment highlights some of the conditions that promoted high linear extension rates in this species. The second objective of this study was to examine the success of corals outplanted from land-based nurseries and to determine whether corals reared in a land-based nursery would show the same growth and survival after transplantation as those reared in a traditional offshore nursery. This was examined in two experiments. In the first experiment, small fragments were outplanted from colonies reared offshore and from colonies reared in a land-based system. In the second experiment, larger colonies reared in the two separate land-based systems were outplanted to the same location. All transplanted corals were monitored for survival, growth, branch number, and incidence of predation, breakage, and disease over one year. Two major storm events occurred during this portion of the study, so the potential for differences in breakage or storm damage were also assessed. There were no significant differences in survival or growth of fragments outplanted from a land-based nursery and an offshore nursery. Colony outplants from one land-based location had better survival and growth than colonies from a second land-based location. Tropical storm activity greatly increased the occurrence of breakage and tissue loss in all groups, resulting in decreases in colony volume and additional mortality. Survival ranged from 85% to 100% after six months, and survival ranged from 70% to 89% after one year and the passing of two tropical storms. Small (5 cm) transplants did not have significantly lower survivorship than large transplants. Overall, the transplant of fragments and colonies raised in land-based nurseries was successful, as measured by growth and survival rates that were comparable to or exceeded those observed for corals raised in offshore nurseries. Large colony transplants exhibited the best survivorship and extension rates, but were also highly prone to breakage.