Award: OCE-1928761

Coral reef ecosystems provide substantial economic resources to the societies of the United States Virgin Islands (USVI) and other US locations in the forms of tourism, fishing and coastal protection. However, reefs are among the most threatened marine environments, and coral disease is having a devastating impact on these valued systems. In early 2019, a multi-species rapid tissue loss disease matching the description of stony coral tissue loss disease (SCTLD) was found severely affecting a reef off the southwest coast of St. Thomas in the US Virgin Islands (USVI). This study examined how this disease affects coral species and compares the microbiology and physiology of disease samples in the USVI to samples from Florida. It also examined how changing the species composition of a coral community affects the spread and impact of the disease. Our studies demonstrated that coral species demonstrated differential responses to disease exposure, with Orbicella annularis showing the highest susceptibility, followed by Diploria labyrinthiformis, Pseudodiploria strigosa, Porites astreoides and finally Montastrea cavernosa at lowest risk for the disease. We identified bacterial taxa enriched in two or more coral species, and identified these as potential "disease indicator bacteria". These 14 taxa spanned the families: Rhodobacteraceae, Prolixibacteraceae, Vibrionaceae, Arcobacteraceae, Flavobacteriaceae, Clostridiales Family XII, Marinilabiaceae, and Saprospiraceae. Across all samples, an unclassified Rhodobacteraceae was present in all species of infected coral. Comparing these taxa to studies of Florida’s disease outbreak revealed that Vibrio, Fusibacter and Thalassobius were in common between this study and those in Florida. These results suggest that there are likely multiple bacteria playing roles in causing this disease. Interestingly, there was a shift in the mucus microbiota of two coral species from a healthy to diseased state in colonies that were exposed to disease but that did not develop lesions. This suggests a promising non-lethal method to sample and detect SCTLD before visual lesions develop. Coral disease is a significant and increasing threat to Caribbean coral reef systems. Overall, this project provided a better understanding of how the abundance of highly susceptible host species impacts the spread of disease during the early onset of a multi-species panzootic and the microorganisms (potentially pathogens) involved in the coral infections. The project contributed to the research training of multiple graduate students, including students two based at the Woods Hole Oceanographic Institution. Results of this project were widely communicated through a virtual public event viewed by over 4000 households as well as through 13 public news stories. Last Modified: 11/06/2020 Submitted by: Amy Apprill