Abstract

The long-spined sea urchin (Diadema antillarum) is a keystone species in Atlantic coral reef ecosystems¹ and is considered a species of "Greatest Conservation Need" by the Florida Fish and Wildlife Conservation Commission (FWC). The species functions as a critically important grazer,² but also is a powerful bio-eroder. Diadema prevents overgrowth of algae on coral reefs but also recycles carbonate, preventing the accumulation of coral rubble and resulting in a substrate that is optimal for recruitment of corals and other invertebrates.³ In 1983–1984, there was a Caribbean-wide mortality event that resulted in a loss of more than 90% of D. antillarum from the region over a 13-month period.^4,5 The decline of D. antillarum in the 1980s was highly suggestive of an infectious etiology although a causative agent was never identified.⁶ In September 1983, two Clostridium spp. isolates were recovered from dying sea urchins in an aquarium receiving unfiltered water directly from Biscayne Bay.⁷ In 1991–1992, there was a second event that resulted in further reduction of D. antillarum populations in the Florida Keys⁸ and densities of the sea urchins remain extremely low in most areas. More recently, an amoeba, Neoparamoeba branchiphila⁹ and bacterial disease¹⁰ have been associated with mortality of Diadema aff. antillarum dying in the Canary Islands, an area that was not impacted by the 1983–1984 event. The State of Florida is considering the use of aquacultured D. antillarum for coral reef restoration in selected areas of the Florida Keys and, given the disease history of this taxa, will include health assessment criteria as part of the permitting process. In preparation for future release of aquacultured D. antillarum, or regional translocation of wild D. antillarum, health assessment protocols were developed for the species. To test the procedures and describe baseline flora 189 wild D. antillarum were collected in March, April and September 2015 from the Lower Keys (n = 46), Middle Keys (n = 71) and Upper Keys (n = 72). Health assessment techniques were standardized and included behavioral and physical parameters as well as necropsy protocols and diagnostics. Baseline immune function tests were also completed on 20 organisms collected from the Lower and Middle Keys in March 2015. Protozoans routinely encountered in the gut are believed to be normal flora; however, the effects of holding time and handling protocols on their abundance merit further investigation. Interpretation of microbial and histologic findings are in progress. The intent of the health assessment protocol is to provide guidelines for the standardized examination of D. antillarum in Florida using lethal and non-lethal techniques. A baseline database for the microbial and protozoal flora of adult and juvenile D. antillarum from the three regions in the Florida Keys has been created. Tissues have been archived at the Florida Fish and Wildlife Conservation Commission's Fish and Wildlife Research Institute in St. Petersburg, Florida for future use.

Acknowledgements

The authors thanks Melissa Gilbert and Morgan Beaton from the Florida Fish and Wildlife Conservation Commission and Kayla Ripple and Theresa Floyd from the University of Florida for technical assistance.

* Presenting author

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