SPATIAL AND TEMPORAL DISTRIBUTION OF ALGAL BIOMASS IN A LARGE, SUBTROPICAL LAKE

Epipelon, epiphyton, and phytoplankton biomass were measured quarterly for one year from 20 stations located throughout Lake Okeechobee, a l arge, subtropical lake located in south-central Florida, USA. Seasonal variability was evident in all algal components. The water column acc ounted for the majority of chlorophyll-a (>90%) in December, March, an d September, but accounted for only 61.1% of total chlorophyll-a in Ju ne. Conservative estimates of total chlorophyll-a biomass ranged from 1300 to 36,600kg for attached algae, and from 41,770 to 206,600kg for phytoplankton. Overall, the greatest epipelon biomass was measured in June, the greatest epiphyton biomass was measured in March, and the gr eatest phytoplankton biomass was measured in December in the pelagic r egion and in June in the littoral region. Stations deep within the lit toral zone had greater epipelic and epiphytic biomass than those locat ed along the fringe zone between the pelagic and littoral zones. Princ ipal components analyses revealed that stations located within the mar sh formed the most distinct groupings. Light-related factors were impo rtant in separating stations along axis I, whereas water chemistry hel ped separate stations along axis 2. Overall, these results suggest tha t epipelon, epiphyton, and phytoplankton communities are responding di fferently to the forcing functions in this large, subtropical lake. Ma nagement decisions influencing lake lever may affect these communities differentially, which in turn, may influence ecosystem processes.