The restoration of Lake Apopka in relation to alternative stable states

• Published in: Hydrobiologia 1999-01, Vol.394 (1-3), p.219-232
• Main Authors: BACHMANN, R. W, HOYER, M. V, CANFIELD, D. E
• Format: Article
• Language: English
• Subjects: Algae; Algal blooms; Animal, plant and microbial ecology; Applied ecology; Aquatic plants; Biological and medical sciences; Ecotoxicology, biological effects of pollution; Eutrophication; Fresh water environment; Fundamental and applied biological sciences. Psychology; Lake beds; Lake fisheries; Lakes; Macroinvertebrates; Nutrients; Plankton; Resuspended sediments; Rivers; USA, Florida; USA, Florida, Apopka L; Water depth; Water management; Wind barriers
• ISSN: 0018-8158; 1573-5117
• DOI: 10.1023/A:1003638329772

Lake Apopka (Florida, USA) changed in 1947 from being a clear, macrophyte-dominated lake, used primarily for fishing, into a turbid algal lake with a poor fishery. The lake has resisted various efforts to reverse the change and restore the previous state. The restoration approach emphasizes the reduction in phosphorus inputs to reduce algal blooms and clear the water. We examined the question of whether a deep-lake approach with nutrient reductions is going to work on this large (area 124 km^sup 2^) and shallow (mean depth 1.7 m) lake, or if techniques such as drawdowns or wind barriers developed for shallow lakes using the theory of alternative stable states are more applicable. The assumptions upon which the current restoration is based are not supported. The poor transparency is due more to resuspended sediments than plankton algae, so the current Secchi disk depth of 0.23 m is predicted to increase to 0.34 m with any reasonable reduction in algal levels. The failure of the macrophytes to become re-established probably is due more to unstable sediments than lack of light reaching the lake bed, and the marsh flow-way developed by the St Johns River Water Management District will be ineffective in removing particles from the lake. It would take more than 300 years to remove the fluid mud and more than 800 years to remove the rest of the low density sediments. We conclude that the loss of macrophytes in Lake Apopka is an example of a forward switch in the theory of alternative stable states, and that it will take more than a nutrient reduction program to bring about the reverse switch to a macrophyte state. We suggest an alternative approach using wave barriers to create refuges for plants, macroinvertebrates, and fish to restore Lake Apopka's largemouth bass fishery.[PUBLICATION ABSTRACT]