Date Awarded


Document Type


Degree Name

Doctor of Philosophy (Ph.D.)


Virginia Institute of Marine Science


Romuald N. Lipcius


Relative importance of predator-prey dynamics and several environmental variables in structuring gastropod and bivalve diversity and distribution was investigated in the subtropical seagrass and macroalgal community of Florida Bay, a highly productive system and primary nursery and foraging ground for finfish and invertebrate predators, including the numerically dominant Caribbean spiny lobster, Panulirus argus. The molluscan assemblage, a primary food source for P. argus in particular, is speciose (75 gastropod and 25 bivalve species) and a significant component of epifaunal and infaunal invertebrate assemblages within Florida Bay. Two experimental areas, located within separate basins and each comprised of two experimental sites, were selected within Everglades National Park. Each site consisted of an array of four replicates of each of four structural treatments designed to manipulate predator abundances and composition. The predator guild associated with experimental structures was monitored at periodic intervals (July 1993 to Aug. 1995), at which time benthic suction samples were taken to evaluate diversity, abundance, and distribution of the molluscan assemblage. Experimental areas were significantly different from each other and were representative of separate subenvironments within Florida Bay. Predator abundances were successfully manipulated locally; experimental structures providing more overhead cover attracted significantly more predators. Predator densities were representative of naturally occurring fauna utilizing seagrass beds rather than abnormally high densities reported in studies utilizing artificial reefs. No significant predation impacts by lobster and finfishes on abundance and species richness of the molluscan assemblage were observed. Predation by P. argus and finfishes did not structure gastropod and bivalve mollusc assemblages in these habitats. Area differences, however, had some influence on prey abundance and diversity given the consistent significant area effects prevalent throughout the data. Moreover, lobsters at densities recorded in this study, can not be considered a keystone or even dominant predator in this system Predation in Florida Bay, as in other tropical and sub-tropical systems, is differentiated in time and space, probably due to habitat heterogeneity, spatial and temporal variability in predator and prey abundances, high diversity of prey, and other factors. The Florida Bay benthic community is likely influenced through bottom-up or physical factors and microhabitat characteristics.



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