p. 23 - 54 CONTRIBUTIONS A L'ETUDE SYSTEMATIQUE DU PHYTOPLANKTON MEDITERRANEEN DEVANT COTES LIBYENNES V.H. Skolka, N. Bodeanu, Anca Roban Institut Roumain de Recherches Marines Constanta Abstract The paper presents the phytoplankton species living in Mediterranean Libyan waters on the basis of 2050 Nansen bottle samples collected during the four expeditions carried out between 1975 and 1976. The authors recorded 597 species: 255 Pyrrophyta, 221 Bacillariophyta (77 planktonic and 147 benthic), 60 Coccolithophoridae and 61 other algal groups. Seasonal variations of the phyto- plankton are also presented. Some comparisons with other geographical zones are made by using the Soerensen index of similarity.