P. 225 - 242 EFFECT OF PHENOL AND BETA-INDOLIL ACETIC ACID ON SOME UNICELLULAR ALGAE Pia Elena Mihnea and Iulia Voinescu Romanian Marine Research Institute Constanta Abstract The work presents the result of some tests on the action of phenol and beta-indolil acetic acid on a few unicellular algae, common in the Black Sea phytoplankton. The tested products change the membrane permeability for the trophic substratum, which causes modification in the rate of utilization of the medium and implicitely the variation of the generating time and of biomass of the studied algae.