Factors influencing the distribution, abundance and growth of Lyngbya wollei in central Florida

Abstract

Fifteen sites in the Kings Bay/Crystal River estuarine system, Florida, were sampled over 1 year to determine the spatial and temporal distribution and abundance of the filamentous blue-green alga, Lyngbya wollei (Farlow ex Gomont) Speziale and Dyck. Monthly biomass (dry weight) of benthic Lyngbya mats was constant at approximately 1 kg m −2 during most of the year, but it decreased from April to July when large mats were observed floating on the water surface. Multiple regression analyses showed that Lyngbya biomass was correlated negatively with conductivity and alkalinity; this is consistent with L. wollei being primarily a freshwater species. In regions of the bay with higher salinities, the vascular macrophyte, Hydrilla verticallata (L.f.) Royle, prevailed. Nutrient influences appeared to be small even though the northeast portion of Kings Bay/Crystal River has high concentrations of nitrogen, phosphorus and calcium. Controlled laboratory studies were conducted to determine the effects of pH, salinity, and nutrients on growth of L. wollei. Optimal growth occurred at a pH of 8.0 and a salinity of 0 ppt (g 1 −1); salinities in excess of 5.25 ppt killed more than 99% of the cells within 2 weeks. Growth of Lyngbya from five Kings Bay stations in six nutrients sources (spring water, NO 3N, NH 4N, PO 4P, NO 3N + PO 4P, and NH 4N, + PO 4P) did not differ among stations, and nutrients additions produced no increases over spring water. Addition of Ca 2+ increased growth of L. wollei at low and intermediate concentrations of nitrogen and/or phosphorus; this partially explains why spring water, derived from the limestone aquifer, produces such good growth of Lyngbya.