Relationship of Seasonal Water Quality to Chlorophyll a Concentration in Lake Manatee, Florida

ABSTRACT

Algal growth causing taste and odor problems in surface drinking water supplies can be costly to treat. A study was conducted to determine the relationship of lake water quality to algal growth in Lake Manatee, Florida, a nitrogen (N)-limited water body. Chlorophyll a (chl a) concentration was used as the indicator of algal density. A number of water quality parameters measured from monthly water samples collected during 1990–1992 were evaluated to determine whether a relationship with algal density existed. Using sensitivity analyses to determine which parameters were most influential, a prediction equation was developed using water temperature, nitrate concentration, nitrite concentration, total N/total phosphorus (P) ratio, and electrical conductivity as the most important independent variables. Existing equations used to predict Chl a concentration, developed from previous research, were also tested for applicability in Lake Manatee's situation (using independent data collected in 1993) and were found to be inadequate. The equation developed from this study (p < 0.01, r² = 0.41) was verified using the same independent data collected in 1993. We conclude that algal density changes resulting in blooms which cause water quality degradation may be predicted based on timely sampling and analysis of key water quality parameters.

Key Words:

• cyanobacteria
• Anabaena circinalis
• Oscillatoria
• algal bloom