CYCLOTELLA-TAXA (BACILLARIOPHYCEAE) IN LAKES OF THE ALPINE REGION ANDTHEIR RELATIONSHIP TO ENVIRONMENTAL VARIABLES

Surface sediment diatom assemblages for 86 Alpine lakes were analysed focusing on the dominant genus Cyclotella and corresponding environmen tal data. The range of morphological variability of the Cyclotella bod anica/radiosa, C. distinguenda, C. ocellata, C. comensis and C. stelli gera complexes was documented. Significance tests included in the cano nical correspondence analysis (CCA) indicated that total phosphorus, c onductivity and surface water temperature were significantly correlate d with Cyclotella taxa assemblage distribution. Numerical species opti ma and tolerances were calculated in respect to these significant vari ables using weighted averaging (WA) regression and calibration. CCA an d WA were able to provide information about the environmental preferen ces of the various morphotypes observed.