Octocoral dynamics over a decade on Florida’s coral reef

In recent decades, studies have documented increased octocoral cover and density on western Atlantic reefs, suggesting their potential to thrive in areas once dominated by scleractinians. On Florida’s Coral Reef (FCR), octocorals are among the most abundant benthic taxa, and octocoral cover has demonstrated resilience, despite frequent acute disturbances that have decimated scleractinian populations. While octocoral cover is an important metric, particularly when assessing broad patterns, it overlooks key demographic processes, such as recruitment and survival, that underpin resilience. This study explored the spatiotemporal trends in arborescent octocorals across FCR using three metrics: percent cover, density, and the recruit density of target species. Using a long-term dataset across FCR from 2013 to 2023, generalized mixed-effects models revealed that temporal variations occurred predominantly at regional habitat scales. Octocoral cover declined slightly in most habitats from 2013 to 2023 (1.67% overall), but density increased overall by 33.7%, indicating a shift in the community composition due to several disturbances during the study period. Recruit density surged in the latter half of the study, leading to an increase in density in some habitats that surpassed pre-disturbance levels. Even though octocoral density was quickly restored by abundant recruitment after these disturbances, successive years of growth and survival were still needed to attain a percent cover equal to pre-disturbance values. Marine heatwaves in 2014 and 2015 had minimal impacts on octocoral cover or density, whereas Hurricane Irma (2017) caused significant region-wide declines in both metrics. The combined effects of Hurricane Ian (2022) and the onset of the 2023 marine heatwave likely drove significant declines in cover and density of octocorals in the Florida Keys and Dry Tortugas at the end of the study period. These findings suggest that some species of octocorals demonstrate a remarkable resilience, with populations recovering rapidly through recruitment following acute disturbances across FCR habitats. This multi-metric approach provides a comprehensive framework for understanding octocoral dynamics and their responses to environmental stressors on FCR.