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 l ake in north-central Florida. Nutrient diffusing clay pots and cylindr ical enclosures were used in the field to test effects of different co mbinations of nitrogen, phosphorus, silica, and carbon on algal standi ng crop and composition of periphytic and planktonic algae, respective ly. Effects of nutrient enrichment on periphytic algae were examined i n two studies conducted 31 May - 8 July and 10 June - 15 July 1991. Nu trient effects on planktonic algae were examined in one study from 13 June - 1 July 1991. Planktonic and periphytic algal biovolume was sign ificantly higher (p < 0.05) when nitrogen and carbon were added in com bination than with treatments without nitrogen, carbon, or nitrogen an d carbon. Treatments with nitrogen and carbon combined resulted in low er algal diversity and dominance by coccoid green algae and Scenedesmu s. Results indicate that carbon and nitrogen can be limiting factors t o algal growth in Anderson-Cue Lake and possibly other lakes of simila r water quality.