Stormwater impact to the freshwater Savannas Preserve marsh, Florida, USA

This study evaluated the water quality effects of both untreated and state- of-the-art treated stormwater on a Florida freshwater oligotrophic marsh ma croinvertebrate assemblage during 1995-96. Twenty sampling sites were distr ibuted throughout the length of the Savannas State Preserve freshwater mars h. Sites received runoff from natural upland areas or one of two major subd ivisions that utilize the Preserve for stormwater disposal. Multivariate an d other statistical tests were used to elucidate differences in the macroin vertebrate assemblage, and to identify specific water quality variables tha t correlated with these differences. Areas of the Preserve that received bo th treated and untreated stormwater were shown to possess macroinvertebrate assemblages that differed from those of natural areas, with the greatest d ifferences being observed in association with untreated stormwater. Areas t hat received untreated stormwater had higher levels of pH, phosphorus, and hardness, and lower levels of dissolved oxygen; while only elevated pH and hardness were documented in areas that received treated stormwater. Several species were identified as important factors driving observed macroinverte brate differences, and the abundances of these species were related to thei r environmental requirements. Several violations of State water quality and aquatic life rules were documented. On the basis of these results, a multi -agency task force has been convened to address the stormwater pollution.