Abstract Introduction Acknowledgments Methods Results Discussion Conclusions References

INTRODUCTION

Molluscs are an abundant and diverse component of the shallow coastal ecosystems of Florida. Two hundred and twenty-one families, 646 genera, and 1407 species of molluscs have been documented from the shallow marine environments of the state (Camp, Lyons, and Perkins, 1998). In Florida Bay alone, 235 species of molluscs were recorded by Lyons (1999) over the course of a three-year sampling period (1994-1996). This diversity can be attributed in part to southern Florida’s position at the junction of two molluscan faunal provinces: the Caribbean and the Carolinian.

Molluscs are an integral part of the Florida Bay ecosystem. Different groups of molluscs are components of the micro-, meio-, and macro-fauna of the bay and as some species pass through their life stages they move from the plankton to the benthos. In addition, molluscs employ a number of feeding strategies, including filter feeding, grazing, scavenging, and carnivory. Consequently, molluscs occupy a number of trophic levels within the ecosystem and they fill many important niches as both predators and prey.

Analyzing historical patterns of change in molluscan assemblages is a very powerful tool in reconstructing the history of an ecosystem. Estuarine molluscs tolerate a wide range of fluctuating environmental conditions, yet on a scale of seasons, their populations will migrate to more ideal conditions (Dame, 1996). Lyons (1996, 1998) has demonstrated molluscan migration within Florida Bay in response to seasonal and annual variations in salinity. Individual molluscs, however, are relatively limited in their movement in post larval stages, and typically provide information about a specific site for the duration of their lifetime. In addition, most molluscs are hard-shelled, and therefore well preserved in cores. Turney and Perkins (1972) related the distribution of molluscan death assemblages to environmental influences. On the basis of these previous studies, and given the ecological preferences of molluscs, we believe changes in molluscan assemblages identify significant perturbations of an environment and filter out "noise" caused by day to day or short-term fluctuations, such as those caused by tropical storms. By understanding the factors controlling modern distributions of molluscs, we can interpret patterns of change in the past, and in turn, predict future responses to human-induced or natural environmental change.