PALEOECOLOGICAL RECONSTRUCTION OF ECOSYSTEM HISTORY FROM OSTRACODE SEASONAL ECOLOGY AND SHELL CHEMISTRY IN BISCAYNE BAY, FL

During the last century, rapid urbanization and the alteration of natural freshwater flow patterns across southern Florida have affected the adjacent Biscayne Bay ecosystem.  To evaluate the possible impacts of human activity on the ecosystem, we conducted paleoecological and geochemical analyses on ostracodes from radiometrically dated sediment cores from several sites in central and southern Biscayne Bay.  We calibrated shell d¹⁸O, d¹³C, magnesium/calcium (Mg/Ca), and species' ecology to water temperature and salinity during a year-long sampling project of modern Biscayne Bay.  Results showed a positive correlation between d¹⁸O_shell and d¹³C_shell measured salinity at 25-30°C water temperature for both Malzella floridana and Loxoconcha matagordensis, although other factors such as temperature also influence isotopic values.  In addition, we found that a positive correlation exists between Mg/Ca and salinity for both ostracode species.  Ecological analysis showed that, in Biscayne Bay, Malzella floridana exhibits a wide salinity tolerance; Loxoconcha matagordensis dominates upper mesohaline, polyhaline and euhaline habitats; bairdiids dominate marine waters; and Peratocytheridea setipunctada lives mostly in oligo-mesohaline habitats.  These results are being applied to the sediment core record covering the last 500-1,000 years.