Responses of oyster-reef organisms to variation in freshwater inflowand their use in the restoration of Southwest Florida estuaries

摘要

In order to assess the value of using community metrics of associated organisms to guide oyster-reef restoration efforts in Southwest Florida, spatial and seasonal patterns of the presence of oyster-reef fishes and decapods were examined over a 42-month period in the Caloosahatchee River. Lift nets containing 5 L of oyster clusters were deployed monthly on intertidal reefs at three sites along the salinity gradient. A number of metrics were calculated as a measure of relative habitat use: organism density, biomass, diversity, richness, and dominance. These metrics were correlated with mean freshwater inflow measured upstream of the study area; mean inflow was calculated for the 30-day sampling period as well as for 30-day lag periods for the previous 6 months. Metrics calculated for the station at the mouth of the Caloosahatchee exhibited the greatest number of significant relationships with inflow compared to stations located upstream or downstream. Species richness, biomass, and diversity were negatively related to inflow, and organism density and dominance varied positively with flow. Furthermore, richness and density were most strongly correlated with inflow at increasing lag periods from upstream to downstream stations. The greatest number of significant relationships was detected for lag times of 1 to 5 months prior to sampling. These results suggest that community metrics respond to freshwater inflow at different strengths and different time scales. Therefore, it is important to consider which metrics are to be optimized prior to the setting of freshwater inflow targets or prior to the selection of restoration sites.