Abstract
Unionid mussel species belong to one of the most threatened invertebrate groups on Earth. Biological invasions, especially those by filtering species, are parti cularly harmful to nati ve Unionidae species. In Poland, a significantly disturbing situati on of native Unionidae is observed in thermally polluted aquatic ecosystems. Such water bodies have favorable conditions for the settlement of alien mollusks, including Sinanodonta woodiana or Corbicula fluminea, whose shells can potenti ally be a beneficial substrate for Dreissena polymorpha. The objecti ve of the presented research was to check whether zebra mussels can hinder the invasion of alien species of bivalve mollusks in thermally polluted waters. Our results indicate that with the increase in thermal polluti on associated with the growing invasion of alien species of bivalves, D. polymorpha infestations of clams decrease considerably, which leads to the conclusion that D. polymorpha does not pose a significantnatural threat to bivalves in the lakes under study.