Zooplankton-trophic state relationships in some north and central Florida lakes

Abstract

In a survey of eight lake systems located in north-central Florida, total zooplankton abundance showed a strong positive correlation (r2=0.87, a=0.01) with trophic state. Zooplankton abundance averaged 1.0 × 105 organisms · m−2 in oligotrophic systems and up to 8.2 × 105 organisms · m−2 in the eutrophic systems. Seasonal variations in total abundance were greatest in the eutrophic lakes where rotifers dominated and periodically produced sharp population peaks (approaching 2.0 × 106· m−2). In contrast, the more oligotrophic systems had relatively stable levels of total abundance and were dominated by copepods. Diversities of the major taxa in the lakes were variable with one to three species of copepods, zero to four species of cladocera, and two to seven species of rotifers dominant at any one time. Planktonic cladoceran communities were often composed of only one or two species. Low cladocera diversity in these subtropical systems was suggestive of increased predation pressure on this group of crustaceans. A comparison of the total crustacean abundance in the Florida systems to those of some of the Great Lakes indicated that lower standing crops of crustacean zooplankton in the Florida lakes may be a response to both predation and temperature.