Abstract
In 1987, the kinetics of alkaline phosphatase activity (APA) of size fractionated planktonic cells were examined to define the relative roles of free (dissolved) APA and the plankton components of mesotrophic Lake Schöhsee. APA activity contributed by the different size fractions was not affected by the concentration of soluble reactive phosphorus present. Dissolved free alkaline phosphatase activity varied over ten fold during the study. A major fraction of APA activity was associated with non-algal particles. The 1–35 μm algal size fractions were responsible for the majority of algal alkaline phosphatase activity.