THE PHYTOPLANKTON AND CHLOROPHYLL A, INDICATORS OF THE WATER QUALITY FROM CIRIC LACUSTRINE COMPLEX

∗∗ Abstract. The purpose of this study was establishing the trophic level of water from Ciric lacustrine complex, based on the algological (phytoplankton) and biochemical criterion (chlorophyll a). The researches were carried out on water samples assayed from 5 stations (Dorobanţi, Aroneanu, Ciric I, Ciric II si Veneţia) during the vernal and summer period of the year 2007. The results reveal the fact that the phytoplankton structure reflects significant differences regarding the trophic level of each of the 5 lakes studied and respectively, the different degree of their pollution. Also, the investigations carried out emphasized the fact that when interpreting the water quality based on the algological criterion must be taken into consideration both the quantitative general data, and the distribution of the great group of algae(Cyanophyta, Bacillariophyta, Chlorophyta si Euglenophyta), their ecophysiological role, the dominant species and the global level of the algae diversity. The analyses of phytoplankton regarding the total number of samples/ml and through the dominant species have emphasized the mesotrophic character of the 5 lakes and the significant pollution of Dorobanţi lake, in the last period of the year and of Ciric lake II in the entire year. The data regarding the quantity of chlorophyll a signal the meso-eutrophic character of the ecosystems investigated and attest that Aroneanu and Dorobanţi lakes are the most polluted ones. According to the season, the concentration of the chlorophyll a also reveals fluctuations with oligotrophic character (in June month - Ciric II) and oligo-mesotrophic (in July and August months- Dorobanţi).