PARENT SESSION
Contributed Oral Session 27: Marine Populations Under Harvest
Monday, August 8, 1:30 PM - 5:00 PM, Meeting Room 519 A, Level 5, Palais des congrès de Montréal
The effects of predator abundance and food availability on the abundance of the sea urchin Diadema Diadema antillarum in Puerto Rico.
Colón-Rivera, Ricardo*,1, Sabat, Alberto 2, 1 University of Puerto Rico at, Humacao, Puerto Rico2 University of Puerto Rico at, Río Piedras, Puerto Rico
ABSTRACT- The mass mortality event of the Caribbean sea urchin Diadema antillarum, first reported by Lessios on January 1983 in Panamá, caused severe reductions in abundance throughout the Caribbean. Absence of this keystone herbivore has been linked to increases in algal cover and to the phase-shifts from a coral- to algae-dominated reefs. There are many studies that describe the population dynamics of D. antillarum, but none of them has been able to clearly describe which conditions are the ones needed for D. antillarum populations to re-establish. The Eastern coast of Puerto Rico presents a gradient of anthropogenic impact, with eutrophicated and over-fished reefs near the main island; reefs with excellent water quality and high abundance of fishes within a marine fishery reserve (MFR) located 40 km from the main island; and over-fished reefs with good water quality located outside the MFR. We used these sites as a natural laboratory. We measured (1) the density of D. antillarum, (2) the abundance of its vertebrate and invertebrate predators, (3) sedimentation rates of the reefs, (4) macro algal cover and composition, and (5) the structural heterogeneity in reefs that can be characterized as presenting the three environmental states described before. We expect to find higher densities on sites that are depleted from predators and present high cover of macro-algae. High densities of D. antillarum inside the MFR would suggest that predation is not an important factor affecting D. antillarum populations.
Key words: Diadema antillarum, Coral reef, Sediments, Predator abundance