| A large focus of coral reef research to-date has been documenting the frequency, causes, and consequences of reefs shifting from dominance by corals to macroalgae, but further consideration of important components of the ecosystem, such as fishes and other benthic organisms, is needed to fully capture reef dynamics. This research investigated patterns of coral reef community composition based on both fish and benthic assemblages in Hawai'i and the Caribbean to provide a broadened perspective on coral reef structure and indicators of change. Data were synthesized in both regions from existing sources and novel methods were developed for creating a unified database framework, which facilitated analysis of fish and benthic data from disparate sources. The status of Caribbean coral reefs varied greatly, with a 12-fold difference in biomass of fishes across 36 locations. Greater biomass and larger sizes of predators and scrapers were associated with greater coral cover and lower macroalgal cover. The state of reefs in Hawai'i was assessed based on the composition of fish and benthic functional groups, revealing five distinct reef regimes that varied ecologically. A degraded regime with low coral and low fish biomass was identified, as well as four other novel regimes that varied significantly in their ecology, including three that were previously considered a single coral-dominated regime. Analyses of time series data reflected complex system dynamics, with multiple transitions among regimes. Finally, metrics of fish and benthic communities that relate to our understanding of resilience on coral reefs were compared between Hawai'i and the Caribbean. Patterns of coral and macroalgal dominance, functional and response diversity, and the relationships between herbivore abundance and benthic state all varied between regions, revealing important differences in what underpins resilience in relatively species-poor geographies. This dissertation provides patterns and metrics of reefs in Hawai'i and the Caribbean that can be used for monitoring and managing ecosystem changes on coral reefs in light of increasing human impacts and global environmental change. |
