CYCLOTELLA-TRIPARTITA (BACILLARIOPHYCEAE), A DOMINANT SPECIES IN THE OLIGOTROPHIC LAKE STECHLIN, GERMANY

Phytoplankton succession was studied weekly based on integrated epilim nion samples in the deep oligotrophic Stechlinsee (Brandenburg, German y) during January-December 1994. The seasonal development of phytoplan kton was basically monomodal with one definite early May maximum (1,35 0 mu(3) l(-1) fresh weight). During the maximum, unicellular blue-gree n algae of picoplanktonic size and Cyclotella tripartita dominated. Th e latter is new for the flora of Germany. This paper describes morphol ogical features of C. tripartita in the Stechlinsee, its population dy namics and growth conditions. An analysis of the known localities for C. tripartita indicates that the species has a north circumpolar distr ibution and its occurrence is predictable for large, deep, oligotrophi c waters with high transparency, neutral or slightly alkaline pH and C a2+ concentrations of 6-46 mg l(-1).