Recovery of the sea urchin Diadema antillarum in the Caribbean Coral Reef Ecosystem

Diadema antillarum (Philippi), the long-spined sea urchin, was once common in Caribbean coral reef ecosystems. In 1983, off the coast of Curacao, approximately fifty percent of the D. antillarum population was found dead or dying due to an unknown disease which continued into 1984 and ravaged the entire Caribbean. A recurrent epidemic occurred in the Florida Keys in 1991 resulting once again in mass mortality of D. antillarum which left the population at about 1% of its previous densities. Over the course of the last two years, a program at Montclair State University (MSU) has been in place to quantify juvenile D. antillarum arriving at coral reefs in the Florida Keys. The goal is to assess the current population status of D. antillarum and keep an ongoing record of the repopulation of the species after the epidemics. To quantify juvenile D. antillarum, we have placed a series of larval collectors at inshore and offshore reefs in the Florida Keys every month since January 2018. After a month in the ocean collecting settling larvae, the contents of the collectors are sorted under a microscope to record abundances of juvenile D. antillarum. We identified 17 juvenile D. antillarum between January and November 2018 from 6 coral reefs. Despite rising counts in the Florida Keys, juveniles are still rare in these coral reefs compared to other places in the Caribbean. Whether the D. antillarum population of the Florida Keys will fully recover from the epidemics remains to be seen.