Date of Award

Winter 2010

Document Type


Degree Name

Doctor of Philosophy (PhD)


Biological Sciences


Ecological Sciences

Committee Director

Mark D. Butler IV

Committee Member

Ian Bartol

Committee Member

Dan Dauer

Committee Member

Alan Savitzky

Committee Member

Robert Steneck


Caribbean coral reefs have undergone a phase shift from a system dominated by corals to one where algae are pervasive. This shift was precipitated by the loss of herbivores, including the mass mortality of the long spined sea urchin (Diadema antillarum), coupled with disease and the recruitment failure of hermatypic corals. Diadema populations have recovered in some areas of the Caribbean, but are still below historical levels in the Florida Keys, likely due to low larval supply coupled with predation on juveniles. Lobsters are sea urchin predators in other systems and the spotted spiny lobster (Panulirus guttatus ) is abundant on coral reefs in the Florida Keys, where I investigated their role as nocturnal, philopatric carnivores on patch reef communities, with particular emphasis on their density and trait mediated impacts on Diadema. Additionally, I examined the importance of predation threat and intra-specific competition on habitat utilization by Diadema. I found that P. guttatus consumes small herbivorous reef invertebrates including sea urchins and crabs and its foraging activities destabilize rubble substrate, a disturbance more intense with smaller rubble, which may inhibit coral recruitment. In addition to density mediated impacts, Diadema increased its flight response and consumed significantly less algae in the presence of P. guttatus. However, Diadema did not increase its flight response to P. argus , a known Diadema predator. Panulirus guttatus cues also mitigated the importance of intra-specific competition for shelter by Diadema, with Diadema selecting shelters with conspecific chemical cues over those with P. guttatus chemical cues. Through its negative impact on the abundance and behavior of herbivores such as Diadema and destabilization of rubble substrates, high densities of P. guttatus potentially contribute to coral-to-algae phase-shifts on coral reefs.


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