ANNUAL PROFILES OF PHOTOSYNTHETIC LIPOPHILIC PIGMENTS IN 4 FRESH-WATER LAKES IN RELATION TO PHYTOPLANKTON COUNTS AS WELL AS TO NUTRIENT DATA

Phytoplankton structure and dynamics of four eutrophic lakes of Berlin were studied in 1992. The biomass change of relevant classes-Cyanophy ceae, Bacillariophyceae, Cryptophyceae, and Chlorophyceae-is well repr esented by HPLC-analysis of photosynthetic lipophilic pigments simulta neously carried-out. Nevertheless, an estimation of algal class biovol umes or phytoplankton composition, on the basis of chromatographically recorded pigment data is restricted to a semi-quantitative considerat ion. Different pigment amounts in individual species of the same algal class or varying marker pigment/chlorophyll-a ratios are discussed as a reason for the misleading pigment-based quantification of phytoplan kton dynamics. However, the analysis of the obtained data points to th e possibility of using HPLC-aided pigment determinations in connection with microscopic cell counting for a detection of variable physiologi cal states under field conditions; provided that mass developments of algae are dominated by a single species as common in eutrophic lakes. For time periods with dominating Planktothrix agardhii or Microcystis spec. a positive correlation was found between their content of the cy anophyte specific pigment echinenone and increasing nitrogen availabil ity. In contrast, no relations could be detected between the changing fucoxanthin content of Aulacoseira spec. and any of the measured envir onmental parameters (nutrient concentrations or light climate).