p. 87 - 108 DONNEES PRELIMINAIRES SUR LA STRUCTURE QUALITATIVE ET QUANTITATIVE DU PHYTOPLANCTON DU LAC SINOE PENDANT LES ANNEES 1973-1977 Anca Roban 1) et Maria Stadniciuc 2) 1)Institute Roumain de Recherches Marines Constanta 2)Direction des Eaux "Siret" Bacau Abstract The qualitative and quantitative data on phytoplankton of Sinoe lake in a five years period, is summarised. The dominant systematic groups had remained the same throughout the period. The Diatomeans have riched a peak in 1976-77 (54.28% and 53.52% respectively); the Chlorophyceans in 1974 (32.05%) and Cyanophyceans in 1975 (25.00%). Also, in all of the years, the freshwater species prevailed, both qualitatively and quantitatively.