EVALUATING THE EFFECT OF THERMAL ANOMALIES ON CORAL REEF BENTHIC COMPETITIVE INTERACTIONS

Climate change has intensified thermal anomalies in coral reef ecosystems, contributing to coral bleaching and decline. As corals die, reef fragmentation increases, and species interactions in the benthos change. However, it is unclear which competitive interactions may prevail and structure future reef ecosystems. The aim of this thesis was to evaluate the effect of thermal anomalies on coral reef benthic competitive interactions. Photoquadrats in southeast Florida reef sites were assessed over 15-years to generate interaction metrics and determine effects on hard coral survivorship. A state-transition model was created to predict the resultant community across 100 years with thermal scenarios concordant with the IPCC RCP 4.5 and 8.5. Interaction doubled across three thermal anomaly events and ended up mainly composed of pairwise examples between Dictyota, Halimeda, Niphates erecta, and Erythropodium caribaeorum. Century projections confirm that soft coral and sponge interactions will increase through thermal anomalies. The survival of hard corals was more successful when colonies were in permanent or intermittent interactions than when colonies were solitary (indirect interactions). Living hard corals were mostly found interacting with the macroalgae, Dictyota, and sponge Aplysina cauliformis, while corals that died were mainly in interactions with the soft coral E. caribaeorum, and sponges N. erecta, C. delitrix, D. anchorata, and Ircinia campana. Future reefs will be composed of more interactions between soft corals and sponges as thermal anomalies intensify, which will result in a patchier and flatter community.