Abstract
The aim of the study was to identify the similarities and differences in the phytoplankton in lakes Licheńskie and Ślesińskie based on the phytoplankton species composition and biomass. Quantitative and qualitative studies of phytoplankton from two heated lakes were conducted in 2004-2005. A total of 280 and 240 taxa were identified belonging to six phyla: Chlorophyta, Cyanoprokaryota, Cryptophyta, Dinophyta, Euglenophyta, and Heterokontophyta. Most of the taxa were incidental species with frequencies of less than 25%. The phytoplankton biomass in Lake Licheńskie ranged from 0.2 to 8.6 mg dm-3. Throughout the growing season of 2004, the phytoplankton observed was comprised of diatoms and green algae, while in 2005 it was comprised of diatoms, green algae, and cryptophytes. The phytoplankton biomass in Lake Ślesińskie ranged from 0.4 to 13.2 mg dm-3. Diatoms dominated in this lake in the spring and fall of both years (54-90%), while in summer 2004 diatoms and green algae dominated and in summer 2005 the dominants were cryptophytes, dinophytes, and cyanophytes.