Diadema antillarum populations in Little Cayman Amanda Mortillaro and Allison Farrar

Introduction Mass mortality of Diadema antillarum in the Caribbean (3) – Most extensive and extreme ever recorded for a marine organism Low recovery rate Increase in adult population increases juvenile population (5) – Well grazed reef Increase in Diadema population is correlated with an increase in coral recruits (4) Greater the density, the smaller the urchins will be (2) Downstream current vs. discrete breeding units (2)

Hypotheses 1. The Diadema antillarum population in Little Cayman is slowly increasing. 2. The south side of the island is more densely populated than the north. 3. As the distance from shore increases, the number of Diadema antillarum decreases. 4.The presence of coral recruits is positively correlated with the density of Diadema antillarum. 5. The presence of predators will affect the density and distribution of the Diadema antillarum population. 6. There is an inverse relationship between Diadema antillarum densities and size.

Methods 30m x 2m transects Number of juvenile and adult Diadema antillarum was noted along with the major predators (Grunts, Queen Triggerfish, and Lobster) Three 2m x 2m quadrats where placed at 0m, 10m, and 20m – Size and number of coral recruits

Snorkel Locations Sampled 1 4

Results

Point of Sand Owen’s Island Jackson’s Bay Preston Bay

Results

No Diadema found at deep dive sites No significant relationship between number of Diadema and coral recruits Grunts were found at every site – Deep sites Queen Triggerfish and lobster were found and no Diadema

Discussion Diadema population has increased dramatically in the past six months – If historical is data is valid Shallow coral is the primary habitat Downstream current is not evident – Greater number in west not east – Perhaps a closed system Greater density of adult Diadema than juvenile – Chance for recovery

Recommendations More transects at each and more sites LAMP surveys in the future should be conducted with a more rigorous methodology like the one we have used – Habitat variability – More information recorded Study relationship between adult and juvenile spatial distances

Works Cited 1. Bak, R.P.M, M.J.E Carpay, and E. D. De Ruyter van Steveninck. "Densities of the sea urchin Diadema antillarum before and after mass mortalities on the coral reefs of Curacao." Marine Ecology- Progress Series 17 (1984): Hunte, W., and D. Younglao. "Recruitment and population recovery of Diadema antillarum in Barbados." Marine Ecology- Progress Series 45 (1988): Knowlton, Nancy. "Sea urchin recovery from mass mortality: New hope for Caribbean coral reefs?" Proceedings of the National Academy of Sciences of the United States of America 98 (2001): Lessios, H. A. "Diadema antillarum populations in Panama twenty years following mass mortality.“ Coral Reefs 24 (2005): Nedinyer, Ken, and Martin A. Moe Jr. "Techniques Development for the Re- establishment of the long-spined sea urchin, diadema antillarum, on two small patch reefs in the upper Florida Keys." Thesis.