PREDICTORS OF SEASONAL OXYGEN LEVELS IN SMALL FLORIDA LAKES - THE IMPORTANCE OF COLOR

This study examines the relationship of profundal oxygen concentration s in 55 shallow Florida lakes to humic color, trophic state, and lake size during different seasons. The data set represented a broad range of color and trophic state. The percent saturation of dissolved oxygen remained relatively constant during the fall (mean 78.4%), winter (me an 81.3%), and spring (mean 82.5%), but declined markedly during summe r (mean 65.2%). Chlorophyll a concentrations were highest during the w inter (mean 2.52 mg m(-3)) and lowest during the fall (mean 1.17 mg m( -3)), while color peaked during the fall (mean 30.1 mg Pt l(-1)) and w as lowest during the summer (mean 12.7 mg Pt l(-1)). The relative impo rtance of lake size, chlorophyll a, and color in explaining variation in percent oxygen saturation was examined using multiple regression. P ercent oxygen saturation was negatively correlated with color during t he winter, spring, and summer, and positively correlated with lake siz e in the winter and spring. However, percent oxygen saturation showed no relationship with chlorophyll a during any season. These results su ggest that colored Florida lakes are naturally oxygen depleted and tha t profundal oxygen values have little relationship to lake trophic sta te.