Phosphorus limitation in reef macroalgae of South Florida

Nitrogen (N) has traditionally been regarded as the primary limiting nutrient to algal growth in marine coastal waters, but recent studies suggest that phosphorus (P) can be limiting in carbonate-rich environments. To better understand the importance of P. alkaline phosphatase activity (APA) was measured in reef macroalgae in seven counties of south Florida ; several significant trends emerged : 1) APA decreased geographically from the highest values in Dada>Monroe>Palm Beach>St. Lucie>Broward>Martin>Lee counties 2) APA varied temporally with increasing nutrient-rich runoff in the wet season 3) APA varied due to taxonomic division Phaeophyta>Rhodophyta>Chlorophyta 4) Nutrient enrichment experiments demonstrated that increased N-enrichment enhanced P-limitation while increased P decreased P-limitation. These results suggest that high APA observed in carbonate-rich waters of Dade County and low APA in Broward County resulted from high nutrient inputs associated with anthropogenic nutrient pollution.