EFFECTS OF NITROGEN, PHOSPHORUS AND CARBON ENRICHMENT ON PLANKTONIC AND PERIPHYTIC ALGAE IN A SOFTWATER, OLIGOTROPHIC LAKE IN FLORIDA, USA

The objective of this study was to investigate nutrient limitation of algal abundance in Anderson-Cue Lake, a softwater clear oligotrophic lake in north-central Florida. Nutrient diffusing clay pots and cylindrical enclosures were used in the field to test effects of different combinations of nitrogen, phosphorus, silica, and carbon on algal standing crop and composition of periphytic and planktonic algae, respectively. Effects of nutrient enrichment on periphytic algae were examined in two studies conducted 31 May - 8 July and 10 June - 15 July 1991. Nutrient effects on planktonic algae were examined in one study from 13 June - 1 July 1991. Planktonic and periphytic algal biovolume was significantly higher (p < 0.05) when nitrogen and carbon were added in combination than with treatments without nitrogen, carbon, or nitrogen and carbon. Treatments with nitrogen and carbon combined resulted in lower algal diversity and dominance by coccoid green algae and Scenedesmus. Results indicate that carbon and nitrogen can be limiting factors to algal growth in Anderson-Cue Lake and possibly other lakes of similar water quality.