Disease dynamics and potential mitigation among restored and wild staghorn coral, <i>Acropora cervicornis</i>

Abstract

The threatened status (both ecologically and legally) of Caribbean staghorn coral, Acropora cervicornis , has prompted rapidly expanding efforts in culture and restocking, although tissue loss diseases continue to affect populations. In this study, disease surveillance and histopathological characterization were used to compare disease dynamics and conditions in both restored and extant wild populations. Disease had devastating effects on both wild and restored populations, but dynamics were highly variable and appeared to be site-specific with no significant differences in disease prevalence between wild versus restored sites. Disease affected up to 80% of colonies at one site following a tropical storm. A subset of 20 haphazardly selected colonies at each site observed over a single field season revealed widely varying disease incidence, although not in a consistent way between restored and wild sites, and a case fatality rate of 8%. Lastly, two field mitigation techniques, (1) excision of apparently healthy branch tips from a diseased colony, and (2) placement of a band of epoxy fully enclosing the diseased margin, gave equivocal results with no significant benefit detected for either treatment compared to controls. Tissue condition of associated samples was fair to very poor; unsuccessful mitigation treatment samples had severe degeneration of mesenterial filament cnidoglandular bands. Polyp mucocytes in all samples were infected with suspect rickettsia-like organisms; no bacterial aggregates were found. Overall results do not support differing disease quality, quantity, dynamics, or health management strategies between restored and wild colonies of A. cervicornis in the Florida Keys.