Abstract >Introduction Study Area Material & Methods Results Discussion Acknowledgements Literature Cited Figures Tables

Knowledge of hydrologic exchange between surface water and ground water is critical to understanding the movement of water and solutes in the Florida Everglades. The Florida Everglades is an extensive subtropical wetland ecosystem that formed during the past 5,000 years when peat and marl were deposited within a pre-existing limestone depression in the southern Florida peninsula (Gleason and Stone 1994). The high porosity of the limestone of the Biscayne aquifer (Fish and Stewart 1991) in South Florida allows for considerable flux between surface water and ground water. In the southern Everglades region, marsh hydrology changed radically during the 1950s and 1960s as a result of the Central and South Florida Project, which impounded and diverted water from the north, draining it eastward and southward by canals through the Atlantic Coastal Ridge. Water depths and hydroperiods (duration of surface water flooding) in Everglades National Park (ENP) were affected dramatically (Loftus et al. 1992). The Comprehensive Everglades Restoration Project is aimed at partly restoring predevelopment flow conditions for the Everglades, as well as considering urban and agricultural needs.

From a hydrological point of view, karst systems are very open, and numerous epigean invertebrates (those living at or above the soil surface) often penetrate the aquifer by means of sinkholes (Gibert et al. 1994b). Surface-water organisms are able to establish some permanent populations in the aquifer because of their ecological tolerance of conditions in the karst-aquifer (Gibert et al. 1994b). Therefore, karstic aquifers contain both epigean and hypogean (those living under- ground) species (Gibert et al. 1994b). The spatial/temporal heterogeneity of the species distribution in karstic habitats depends on the structural heterogeneity and hydrologic functioning of the areas (Rouch and Danielopol 1997). The assessment of species richness in ground water requires a sound taxonomical knowledge of both the hypogean and the epigean fauna, as well as a good knowledge of their ecology, biogeography, and the stratigraphy and lithology of the aquifer, especially pertaining to aquifer permeability. Stygobites (exclusively ground water dwelling animals) are considered indicators of a negligible influence of surface water, whereas the presence of stygophiles (organisms commonly living in surface waters but able to survive and reproduce in ground water habitats if the habitats are not too constraining) points to a connection with surface water (Husmann 1971).

Seepage information is scarce for ENP and the area along its borders. The seepage along the L-31N canal which conveys water into Taylor Slough is important, because water seeps into and out of ENP from this canal. In this study, we analyzed the stratigraphy and lithology of the limestone on the L-31N canal system that runs along the northeastern border of ENP and outside ENP, identifying the high porosity layers. Then, we coupled this information on limestone porosity with a study of subterranean copepod populations, drawing from our knowledge of the epigean and hypogean copepod fauna of ENP from previous research (Bruno et al. 2000, 2001, 2002a, 2002b, 2003). We assessed the depth and extension of the high porosity layers, and we used microcrustacean assemblages to evaluate the degree of exchange between surface water and ground water near canals, especially at levels in the wells where high porosity connections to the canals exist.