Relating Algal Bloom Frequencies to Phosphorus Concentrations in Lake Okeechobee

Abstract

ABSTRACT Empirical relationships were developed between algal bloom frequencies and total phosphorus concentrations for three distinct regions of Lake Okeechobee, and hypotheses were derived to explain observed spatial variation in those relationships. The analyses were based on water quality monitoring data collected monthly between 1986 and 1993, at 10 open-water stations, 12 north littoral stations, and 14 south littoral stations. Using a cross-tabulation procedure, phosphorus/bloom-frequency relationships were developed for bloom criteria of 10, 20, 30, 40, 50, and 60 μg L−1 chlorophyll a. For bloom criteria in the range of 40 to 60 μg L−1 chlorophyll a, blooms were not detected when phosphorus was less than 30 μg L−1, During the 1986–1993 monitoring period, this threshold phosphorus concentration was exceeded 3% of the time in the open lake, 25% of the time in die north littoral, and 48% of the time in die south littoral. When phosphorus concentrations were between 30 and 60 μg L−1 in die littoral re...