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Florida’s springs are internationally noteworthy in their number and magnitude but this natural artesian wealth has declined in modern times. Prominent springs have seen declining flow rates, increasing nitrate concentrations, increasing populations of filamentous benthic algae and invasive aquatic plants, and substantial restructuring of fish and invertebrate communities.
The changes in springs are manifestations of changes in the Floridan Aquifer, the major source of freshwater for public water supplies and agriculture in Florida. The Floridan aquifer together with the terrestrial systems that recharge its water and elemental constituents and its artesian springs might aptly be called the karst ecosystem. The ecological roots of the springs extend into and through the karst ecosystem and effects on any aspect of this ecosystem are expressed in the springs. As such, the springs are the final expression of the status of the karst ecosystem and management of the springs is tantamount to management of the karst ecosystem.
Improved understanding of the karst ecosystem is necessary but is confounded by the fact that its hydrogeologic structure is hidden beneath the land surface. Further, knowledge of its biogeochemistry is rudimentary. Substantial variation in spring flows and water quality indicates considerable heterogeneity in the hydrogeological structure and biogeochemistry of the karst ecosystem. Although the system may be dominated by porous media flow, conduit and fracture flow can also create networks of groundwater flow. The picture for nitrogen, a pollutant of major concern in the springs, is also complex with considerable variation in source loading rates and forms, transformation rates, and loss rates within the karst ecosystem.
The belief that sources near the springs are the best targets for management might aptly be called the “proximity hypothesis”. However, as a consequence of geohydrologic and biogeochemical heterogeneity, areas of a springshed distant from the spring vents could be more significant sources of water and pollutants than are areas nearer the spring vents. This alternative perspective might be termed the “network hypothesis”. To the extent that the network view is more apt, it calls for a deeper understanding of the flow networks of the karst ecosystem.
To provide adequate guidance for regulatory and management programs, springs research must be integrated across the breadth of the karstic ecosystem. Integrated research is now underway through the Collaborative Research Initiative for Springs Protection and Sustainability, a cooperative program between the St. Johns River Water Management District and the University of Florida.
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