COS 270-1 - By altering coral reef benthic assemblages, Stony Coral Tissue Loss Disease threatens reef fish communities

Abstract: In less than a decade, Stony Coral Tissue Loss Disease (SCTLD has caused widespread mortality of susceptible coral species in Florida and the Caribbean, thereby changing reef composition in these regions. Our study assesses a) benthic community responses to SCTLD in the US Virgin Islands (USVI) and b) associations between benthic and fish assemblages in the Caribbean to predict how SCTLD will impact reef fish communities. We used detailed reef community data collected throughout the SCTLD epidemic by the Territorial Coral Reef Monitoring Program (TCRMP) in the USVI and Bayesian models to assess how SCTLD has altered benthic communities. Then, we built a Bayesian Structural Equation Model (SEM) with data from the National Coral Reef Monitoring Program (NCRMP), which spans coral reefs in the USVI, Puerto Rico, and Florida, to analyze existing relationships between (a) biomass of herbivorous, coral-associated, and generalist fish and (b) the benthic functional groups found to respond to SCTLD in the first part of our analysis. We found that in the USVI, SCTLD spread was linked to reductions in SCTLD-susceptible species and increased cover of cyanobacteria, crustose coralline algae, and sponges. Our SEM revealed that SCTLD-susceptible corals are beneficial to fish communities both directly and indirectly via their contributions to rugosity and other benthic spaceholders. However, fish also benefitted directly from SCTLD-resistant coral and rugosity. Because of this, we predict that while reef fish communities are threatened by loss of SCTLD-susceptible species, their positive associations with other benthic species will help buffer the impacts of the disease.