Spatial and temporal distribution of algal biomass in a large, subtropical lake

Abstract

Epipelon, epiphyton, and phytoplankton biomass were measured quarterly for one year from 20 stations located throughout Lake Okeechobee, a large, subtropical lake located in south-central Florida, USA. Seasonal variability was evident in all algal components. The water column accounted for the majority of chlorophyll-a (>90 %) in December, March, and September, but accounted for only 61.1% of total chlorophyll-a in June. Conservative estimates of total chlorophyll-a biomass ranged from 1300 to 36,600kg kg for attached algae, and from 41,770 to 206,600kg kg for phytoplankton. Overall, the greatest epipelon biomass was measured in June, the greatest epiphyton biomass was measured in March, and the greatest phytoplankton biomass was measured in December in the pelagic region and in June in the littoral region. Stations deep within the littoral zone had greater epipelic and epiphytic biomass than those located along the fringe zone between the pelagic and littoral zones. Principal components analyses revealed that stations located within the marsh formed the most distinct groupings. Light-related factors were important in separating stations along axis 1, whereas water chemistry helped separate stations along axis 2. Overall, these results suggest that epipelon, epiphyton, and phytoplankton communities are responding differently to the forcing functions in this large, subtropical lake. Management decisions influencing lake level may affect these communities differentially, which in turn, may influence ecosystem processes.