Algal Responses to Long-Term Nutrient Additions

Periphyton is an important part of the food web and is an integral part of the Everglades ecosystem (Wood and Maynard 1974; Browder et al. 1982). During the late summer and fall, thick mats floating at the surface, growing attached either to macrophytes or at the bottom, are among the most conspicuous components of unenriched open water habitats in the Everglades (Van Meter-Kasanof 1973; Gleason and Spackman 1974; Swift 1984).

Changes in periphyton standing crop, species composition, and productivity along an eutrophication gradient in the Everglades indicate that phosphorus affects the composition and growth of the periphyton community (Swift and Nicholas 1987; Vymazal et al. 1994; McCormick and O’Dell 1996; McCormick et al. 1996, 1998; Pan et al. 2000). Experimental manipulations of nutrients demonstrate that phosphorus also has a negative effect on the development of the calcareous periphyton assemblage (Ornes and Steward 1973; Hall and Rice 1990; Stevenson and Richardson 1994, 1995). Enriched Everglades habitats develop periphyton that is dominated by green algae and eutrophication-tolerant diatoms and cyanobacteria (blue-green algae, Cyanoprokaryota) (Swift and Nicholas 1987; Raschke 1993). However, no studies have ever determined the ecological importance of each algal group in the Everglades by assessing changes in their biovolume along a nutrient gradient.