Project: RAPID: A comparison of acute heat stress and fish abundance influencing coral survival.

NSF Award Abstract
Rising global temperatures continue to place coral reefs in severe peril. The symbiotic relationship between corals and their algal symbionts breaks down under extreme temperatures leading to the expulsion of these protective algal cells, a process known as coral bleaching. Without these algal symbionts, transparent bleached corals are vulnerable to elevated UV light exposure which can be lethal, yet some corals show higher resilience and recovery of their algal symbionts after the extreme heat has passed. One potential reason for increased resilience may be positive interactions with reef fishes that associate with corals. Many reef fish graze directly on coral polyps or on harmful fleshy algae that compete with corals for space and nutrients. As these reef fish establish territories on and around coral, they have the potential to benefit corals through increased movement of water, fecal deposition of nutrients and algal symbionts, and in some cases even shading from direct sunlight. This research leverages a mass coral bleaching event in the Florida Keys to investigate how reef fish-coral associations influence coral survival and recovery from bleaching, increasing our understanding of the importance of reef fish populations for survival of corals in a warming world. The project includes training for undergraduate and graduate students and incorporation of the research into an ongoing marine science STEAM program for children. The results of this research have implications for coral management and restoration. Exceptionally warm waters off the southern tip of Florida in summer 2023 initiated a mass coral bleaching event in the Florida Reef Tract, the third largest barrier reef in the world. Herbivores (parrotfishes and damselfishes), corallivores (butterflyfishes), and cleaner gobies play critical roles in modulating coral-macroalgae competitive interactions. This project tests the hypothesis that reef-fish coral interactions influence the recovery of bleached corals, thereby affecting coral reef community structure. A total of 240 individual corals across 15 sites in the middle Florida Keys are being marked and photographed to measure their degree of bleaching. Underwater camera deployments record the species and number of reef fish present, allowing for quantification of fish behaviors and coral association times. Pre-bleaching observations and data from four timepoints following the bleaching event are being compared to examine the relationship between fish-coral associations, abiotic factors, and fate of individual corals. The results will advance understanding of coral resilience to bleaching events and the role of reef fishes during the recovery period. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.