PATTERNS IN PHYTOPLANKTON COMMUNITY STRUCTURE IN FLORIDA LAKES

We demonstrate, based on examination of phytoplankton communities from 165 lakes located throughout Florida, the existence of smooth gradients of change in phytoplankton community structure with increasing lake trophic status. This change involves a gradation from a tendency toward the dominance of green algae in oligotrophic lakes to dominance of cyanobacteria in eutrophic and hypereutrophic lakes, with a peak in diatom abundance in mesotrophic lakes. The mean biomass of the dominant genera within these groups was not related to the biomass of the communities where they occurred; instead, it was strongly related to their size, the (geometric) mean biomass of the genera increasing as the 0.74 power of their cell volume.