Ex situ treatment enhances survival and recovery from stony coral tissue loss disease in Caribbean corals

Caribbean coral reefs have experienced significant genetic loss from the effects of stony coral tissue loss disease (SCTLD). Since its emergence in 2014, SCTLD has spread from Florida to the Caribbean, affecting at least 25 species of scleractinian corals. Mitigation strategies are needed to combat this disease that has already altered reef functionality and driven highly susceptible species, such as Dendrogyra cylindrus , to functional extirpation in parts of their native range. Current treatment methods have been shown to be effective at quiescing SCTLD lesions, but they have limitations. This study examines the efficacy of a holistic 10-day ex situ SCTLD treatment approach aiming to arrest lesion progression, support tissue recovery, and promote survival. Coral fragments affected with SCTLD-like lesions from five Caribbean coral species received treatment and experienced 93% survivorship with no signs of reinfection for 352 days post-treatment. Non-treated (control) fragments experienced 70% mortality by day 26 of the study. The same 10-day treatment was conducted on day 26 for the remaining control fragments, resulting in 100% survivorship with no signs of reinfection for 336 days post-treatment. These results suggest that the ex situ treatment examined offers an effective and accessible tool to retain valuable genetic stock for SCTLD-susceptible species, particularly threatened and endangered taxa with already reduced genetic diversity.