Site-specific variability in recovery of Caribbean sponge communities following two category-5 hurricanes Coral Reefs

Coral reefs worldwide are increasingly subjected to multiple disturbances, including storm events, thermal anomalies, disease outbreaks and more localized stressors. Climate change is predicted to increase the frequency and severity of tropical cyclones. In 2017, an unprecedented event of two Category 5 hurricanes in rapid succession occurred on St. Thomas, United States Virgin Islands. Short-term monitoring (2.5 months after the hurricanes) enabled us to characterize the impacts of these extreme events on coral reef sponge communities. In addition, to understand how coral reefs recover after disturbance, we evaluated changes in the sponge communities from pre-hurricane surveys in 2016 to two years post-storms in 2019. We identified 148 distinct sponge taxa within permanent transects at six sites around St. Thomas. Sponge communities varied across sites pre-storms, and exhibited different degrees of resilience. By two years post-storms, sponge cover did not return. Sponge volume increased overall, but was highly variable among sites. However, after two years, sponge densities increased by 42.3% over pre-storm densities, indicating the occurrence of sponge recruitment and fragmentation/reattachment. Sponge community richness increased at all sites over time, with an influx of rare species. Overall, succession of sponge communities was gradual and variable across sites and points to post-hurricane recovery requiring longer than two years. Although none of the sites returned to their pre-storm assemblages, recovery was greater at some sites at two years post-storms. Our data suggest that sponge recovery may occur on USVI reefs, but requires a longer timeframe and an absence of subsequent disturbances. Grant no. NA15NOS4820074