Frequent disturbances and chronic pressures constrain stony coral recovery on Florida’s Coral Reef

Acute disturbances and chronic pressures have an important and increasing influence on the structure of coral reef communities. For the viability of benthic taxa such as stony corals, a balance between loss following disturbance and recovery is vital. Coral populations on reefs with lower exposure to chronic pressures are often presumed to have increased resilience, enabling them to recover quickly following disturbance, but decades of anthropogenic stress and degradation may undermine the systematic recovery and reassembly of benthic communities. This study explored spatiotemporal changes in benthic community structure over a 15 yr period at three distinct coral reef regions with a gradient of chronic pressures in Florida, USA, (southeast Florida, the Florida Keys and the Dry Tortugas). We specifically assessed the spatial scale, potential drivers of change and resilience in stony coral, octocoral, sponge and macroalgae cover. Spatiotemporal changes were assessed at four different scales: among regions, habitats, sub-regions, and habitat types within regions. Cover of stony corals remained very low or declined in every region from 2004 to 2018, with corresponding increases in macroalgae cover. Stony coral recovery was limited regardless of regional differences in chronic pressure. Octocorals exhibited greater resilience due to increased recovery following disturbance and generally had higher cover than stony corals on Florida’s Coral Reef, while sponge cover was very stable over the study period. Acute disturbances, which affected sites on average once every 3 yr, negatively impacted stony coral and/or octocoral cover in every region and habitat, contributing to the regionwide proliferation of macroalgae. This study determined that high disturbance frequency and chronic anthropogenic pressures on Florida’s Coral Reef have led to sustained declines in stony corals and corresponding proliferation of macroalgae. Stony corals were expected to recover during inter-disturbance periods, but in Florida, even in locations with lower chronic pressure, recovery is severely limited.