A Synthesis of Coral Reef Community Structure in Hawai‘i and the Caribbean

Mary Donovan, Department of Zoology
Friday, December 16, 2016 - 3:30pm to 4:20pm
BioMed B-103

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. However, focusing solely on coral and macroalgae as indicators of reef change ignores other important components of the ecosystem, such as fishes and other benthic organisms. 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 and analyzing 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 39 locations. Differences in ecosystem state across the Caribbean were predicted by metrics of fish assemblage structure including overall fish biomass, biomass of fish functional groups, and mean size by functional group. Reefs in Hawai‘i were assessed based on the composition of fish and benthic functional groups to reveal five distinct reef regimes that varied ecologically. Analyses of time series data reflected complex system dynamics, with multiple transitions among regimes. Metrics of fish and benthic communities that relate to our understanding of resilience on coral reefs were also 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. Together, these results suggest that simplistic dichotomies are not sufficient to describe the status and trends of coral reefs, and a nuanced understanding of reefs in is necessary for monitoring and managing ecosystem changes on coral reefs in light of increasing human impacts and global environmental change.