Abstract
Resource managers are often tasked with restoration, yet rarely know the baseline, pre-alteration conditions. One procedure is to infer subrecent history from paleoecologic, taphonomic, or geochemical indicators. Rarely does one method produce a unique and reliable solution. We therefore employ a multi-disciplinary approach to the restoration of altered estuaries in Southwest Florida. Water management practices within two estuaries located within the Rookery Bay National Estuarine Research Reserve have negatively affected water quality and ecosystem health. Water flow to these estuaries is scheduled for restoration within the next decade. Our group is comparing: oyster distribution and productivity (an indicator species for salinity effects), life and death assemblages of molluscs (to establish a pre-alteration community composition), and carbon and oxygen isotopic composition of subrecent oyster shells (to infer paleosalinity and paleotemperature [subsequent talk]). These comparisons are made among pristine and altered estuaries at spatially homologous points (exhibiting similar geomorphology along estuarine gradients). Oyster reef distributional patterns within altered estuaries suggest that the foci of oyster recruitment have shifted historically. Oyster productivity varies similarly with the highest values within the most-altered watersheds shifted seaward relative to pristine systems, as predicted by the greater volume of freshwater. Oysters track the location of mesohaline water where primary productivity tends to be greatest. These data suggest that water flow engineering practices should restore mesohaline waters to their pre-alteration location (i.e., at the homologous position exhibiting highest oyster productivity in the pristine estuaries). Analysis of infaunal molluscan death assemblages reveals that community distribution patterns vary between pristine and altered estuaries. The altered estuary appears to have stronger infaunal benthic community gradients than the pristine estuary, suggesting that pre-alteration community composition is more homogeneous. Continued analyses will discriminate between salinity vs. substrate effects within and between the estuaries.