Ground water flows to lakes are being quantified using models. Ground-water exchange with 10 lakes was estimated using water budgets and geochemical tracers. Another study used nitrogen isotopes to identify sources of nitrate in the shallow ground water around lake basins. Analysis of seismic profiles for each lake showed that central Florida lake development follows four sequential stages to maturity. Seismic profiles also were used to locate possible breaches in the confining layer that maintains water levels in the lakes.
Studies indicate that fertilizer is a major source of nitrogen and phosphorus in south Florida.
Estimated annual nitrogen loads are highest in outflows from the Caloosahatchee River basin and the major Palm Beach canals, and lowest in outflows from parts of the Big Cypress basin. Annual phosphorus loads are highest in the Peace River, and are also high in the Caloosahatchee River and major Palm Beach canals. Results of the 3-year intensive sampling program show that nutrient concentrations vary widely both seasonally and spatially in response to human and natural influences. DDT compounds were detected in 25 of 27 fish samples in 1995, sometimes in concentrations comparable to those detected in fish in the early 1970's. Ecological studies in south Florida were completed to determine the abundance and diversity of fish, invertebrates, and algae.