Research on phytoplankton was carried out during 2019, samples were collected from lower sector of Dniester river, part of Republic of Moldova. Sampling and analysis of phytoplankton was carried out by conventional hydrobiological methods [1,2]. During 2019 year the diversity of quantitative parameters of phytoplankton, as well as the water quality, using algae species as indicators of saprobity were assessed. In phytoplankton compositions of the lower sector of Dniester River were identified 40 species. It was found that the phytoplankton species of the following groups predominated: Cyanophyta-4, Bacillariophyta-26, Chlorophyta-7 and Euglenophyta-3. The basis of the floristic diversity consists of species: Aphanizomenon flos-aquae, Synechocystis aquatilis, Oscillatoria lacustris from green algae, Cocconeis placentula, Cyclotella kuetzingiana, Gomphonema olivaceum, Navicula cryptocephala, Nitzschia acicularis from diatoms algae, Monoraphidium Komarkovae, Dictyosphaerium pulchellum, Monoraphidium contortum and Scenedesmus quadricauda from green algae, Euglena polymorpha, Monomorphyna pyrum and Trachelomonas hispida from Eulglenophyta algae. The number of phytoplankton species in Dniester River lower sector was in limits 1.35-17.65 mln. cell/l, with higher values at Sucleia and Palanca stations of collecting samples. It was attested the preponderance of Cyanophyta (Synechocystis aquatilis) in the forming of the number of algae species, during spring and autumn. The biomass of planktonic algae was in limits 0.61-8.47 g/m3, with the high value in spring. The main part in the formation of phytoplankton biomass was Bacillariophyta algae. The saprobic index values were established within 1.87-2.39, being higher in summer time. The values of saprobic indices were estimated on the basis of species-indicators (33 species) from phytoplankton composition, which were in proportion of 55 % typically β-mezosaprobic (Aphanizomenon flos-aquae, Nitzschia sigmoidea, Synedra ulna, Trachelomonas hispida, Pediastrum boryanum, Scenedesmus quadricauda), 15% - α-mezosaprobic (Navicula cryptocephala, Nitzschia palea, Euglena polymorpha). According to these indices, the water quality of Dniester River lower sector was attributed mainly to II-III (good-moderately polluted) quality classes.

References:
1. Ungureanu Laurentia,; Tumanova Daria Sampling of phytoplankton. In: Ghid de prelevare a probelor hidrochimice şi hidrobiologice=Hydrochemical and hydrobiological sampling guidance. Programul Operaţional Comun România-Ucraina-Republica Moldova 2007-2013; Chişinău 2015; p.12-14
2. Regulament cu privire la cerinţele de calitate a mediului pentru apele de suprafaţă. Anexa 1. publicat: 22.11.2013 în Monitorul Oficial Nr.262-267, art. Nr.1006, 2013, p. 32-39.