Impacts of the spotted spiny lobster (Panulirus guttatus) on the long-spined sea urchin (Diadema antillarum) and patch reef communities in the Florida keys

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.