Impacts of a Natural Disturbance on Coral Reefs in the Florida Keys and Subsequent Recovery Potential of the Sea Urchin Diadema antillarum

Ecosystem resilience is a measure of an ecosystem’s capacity to resist abrupt change and recover following a disturbance. While stochastic disturbances can contribute to normal ecosystem functioning, mounting natural and anthropogenic stressors are simultaneously intensifying the severity of disturbances and reducing the capacity for ecosystem recovery. Here, I examine the impacts of hurricane disturbance on a coral reef ecosystem and the potential for post-storm population recovery of a keystone herbivore, the sea urchin Diadema antillarum. Grazing pressure exerted by dense populations of D. antillarum is critical to coral reef ecosystem health by preventing (or reversing) an ecological regime shift from coral- to macroalgal-dominated reefs following disturbance. Hurricane Irma, a Category 4 Hurricane, made landfall in the Florida Keys in September 2017. The effects of the storm on D. antillarum and the surrounding coral reef community were evaluated at 10 sites in the middle and upper Florida Keys. Following Hurricane Irma, D. antillarum densities declined by 80% and the coral reef community was significantly altered. To assess the potential for local D. antillarum recovery, larval influx and subsequent increases in adults were measured using artificial settlement plates and transect surveys, respectively. Larval influx did not yield a measurable increase in adults over the period of the study, indicating limits to post-storm population recovery. The reestablishment of D. antillarum populations seems unlikely without extensive management efforts. Enhancing herbivory on coral reefs will be essential to building ecosystem resilience in the face of an increasingly severe disturbance regime