Initial assessments of a potentially novel coral disease affecting key reef building corals on Florida’s Coral Reef

A potential new coral disease, currently coined Fast Lesion Progression (FLP), has been observed affecting coral reefs across the Florida Keys. FLP manifests as large, quickly spreading lesions on Orbicella faveolata colonies, often accompanied by sloughy tissue at the lesion line. To investigate this potentially novel disease, we tagged and monitored 51 corals across three Florida Keys reef sites. We reexamined photos from 234 of the first O. faveolata colonies treated at six sites and found that 20.5% of presumed SCTLD-affected O. faveolata were instead FLP- style lesions, with offshore Upper Keys reefs having a higher percentage of historic FLP-affected colonies than other sites. 3% of colonies were affected with both SCTLD and FLP concurrently. We assessed photos of 40 amoxicillin-treated lesions from 2019-2020 and 2022-2023 and found treatment efficacy to be 45%, and an additional 23 from 2022-23 for which efficacy was 17.4%. Finally, we collected 220 samples, including TEM, histology, and microbiome samples, from FLP-affected corals as well as unaffected control corals for further analyses and comparison to previously studied coral diseases by collaborators. FLP has been observed to be a relatively prevalent and highly virulent threat to O. faveolata colonies, which are a vital reef building species. We recommend the prioritization and funding of continued work on this topic to determine other aspects of the disease, such as seasonality, as well as potential treatments to stop the progression of lesions.