Alternate Title

Red-tide–associated Mass Mortality in 2005 of the Sand Dollars Encope aberrans, Encope michelini, and Mellita tenuis (Echinodermata: Echinoidea) on the Central Florida Gulf Coast Shelf


In March 2005, populations of Encope aberrans and E. michelini found at 20-m depth (ca. 27 km west of Captiva Island) and of Mellita tenuis at 6.5-m depth (ca. 7 km west of Egmont Key) were studied to calculate density and size frequency distribution. All individuals were alive. A red tide occurred on the central Florida Gulf Coast shelf during the summer. In Sept., all individuals in these populations were dead. Dead individuals had lost their spines and were gray but intact, indicating recent death. On the same date, all E. michelini and E. aberrans were alive in a population at 20-m depth (ca. 26 km north of the site off Captiva Island and ca. 23 km west of Gasparilla Island). All individuals in a population of M. tenuis at 2-m depth immediately offshore Fort De Soto Park were alive 1 mo after the observation of complete mortality off Egmont Key. All E. aberrans at a site 28 km southwest of Egmont Key were dead in Oct. In May 2006, live E. michelini occurred at the Captiva site at the same density as in March and Sept. 2005. Their large size indicates their origin was by migration from nearby areas unaffected by the red tide.