The examined period is characterized by small floristic variety and well advanced eutrophication process. By the phytoplankton qualitative analysis it has been noted the domination of Bacillariophyta algal division. The values of density on phytoplankton population and their biomass show the domination of bluegreen algae, before each other, that of the species Gomphosphaeria lacustris Chod. As the consequence of the eutrophication, these algae develop intensively, up to the degree of water blossoming. The very high concentrations of the primary and secondary nutrients have also been noted. The trophic status of the reservoir on the basis of OECD classification can be defined as eutrophic.

In this paper we have presented the results of the investigations of phytoplankton carried out in the river Old Begey, from April 2003 till February 2004. The presence of 116 algal taxa of which 10 Cyanobacteria, 20 Euglenophyta, 50 Bacillariophyceae, 3 Chrysophyceae, 30 Chlorophyta and 3 Dinophyta was recorded. In the river Old Begey some rarer brackish species Entomoneis alata and Bacillaria paradoxa have also been found. The index of saprobity given on the basis of Pantle-Buck method indicated that the quality of water of the river Old begey belonged to beta-alfa-mesosaprobic category.

The puddle Slatina is the old meander of the river Tamis. It is periodically fill with moderate salt and high alkaline (pH 9) water. During our investigation it was determined 65 algal taxa from 5 divisions. Qualitative analysis points out on the domination of Cyanophyta, Euglenophyta and Chlorophyta, while quantitative analysis indicate the dominance of Cyanophyta. During spring 2003, total number of algae was 1.026 x 10**6 cel/l. High values of chlorophyll a (20 microgram/l) and total number of algae, as well as low transparency point out the progressive eutrophication.