GSA Annual Meeting in Seattle, Washington, USA - 2017

Paper No. 84-1
Presentation Time: 9:00 AM-5:30 PM


CHIN, Courtney T., Department of Invertebrate Zoology and Geology, California Academy of Sciences, 55 Music Concourse Dr, San Francisco, CA 94118,

The carbonate marine environments of San Salvador, The Bahamas, provide diverse habitats for species integral to maintaining coral reef resilience, namely those species that facilitate the control of macroalgal abundance. One such species, the long-spined sea urchin Diadema antillarum, has been described as the most important bioeroder in reef systems and is generally responsible for inhibiting macroalgal blooms when herbivorous fish stocks decline and nutrient inputs increase. Identifying potential source populations of the species in areas where coral abundance is low may be key to reestablishing historical reef community structure and diversity. This study examines the population distribution and density of D. antillarum in several reef, mangrove, seagrass, and sand habitats around the island of San Salvador. D. antillarum was found in three primary locations of the island in depths ranging from 0 – 6 ft: Pigeon Creek (24.0326˚, -74.5248˚), Grotto Beach (23.9634˚, -71.4889˚), and Fernandez Bay (23.9544˚, -74.5601˚ and 24.0329˚, -74.5249˚). Density profiles for each locality were calculated along transects and test diameters were recorded. The Pigeon Creek population had the highest mean density (0.160 urchins/m2) and the largest median test diameter (8.66 cm) while Fernandez Bay had the second largest mean density (0.094 urchins/m2). Microhabitat choice (high vs. intermediate vs. low protection) varied according to test diameter (X2 = 85.766, p < 0.001), with smaller individuals exhibiting a preference for high protection habitats and larger individuals exhibiting a preference for low protection habitats. Aggregative behavior, defined as individuals with spines interlocking with adjacent neighbors, was only exhibited by larger individuals (Χ2 = 19.610, p < 0.001). Data suggests that the occurrence of Diadema antillarum in San Salvador is patchy and rare. Further implementation of protective measures may be necessary to sustain the species locally, preserve functional redundancy, and support reef recovery through reoccurring disturbance events.