EN
Thirty two populations of Dreissena polymorpha (Pall.) from Poland were electrophoretically studied with respect to enzymatic loci Got1, Est1, Pgi1, Mdh1, Me1, Idh1 and Pgm1. The variation analysis focused on the possible differences between populations inhabiting lakes of different character. Populations from heated lakes displayed a higher genetic variation compared to unheated reservoirs. Populations from brackish waters showed an excess of homozygotes (loci Got1 and Pgi1) compared to freshwaters. Gradual eutrophication of lakes seems to cause no significant changes in the genetic structure of zebra mussel populations.