During the researches of the planktonic algae of the Răut river basin within the limits of the urban ecosystem (EU) Bălţi, years 2020-2021, we identified 93 species and varieties of algae from 5 phyla: Cyanophyta - 13 species, Chlorophyta - 31 species, Bacillariophyta - 30 species & 3 varieties, Pyrrophyta - 2 species, Euglenophyta - 14 species. In the plankton of the tributary of the river Răut - Copăceanca, we recorded the greatest floristic diversity, represented by 60 species and 2 varieties. The indicator spectrum is represented by 77 species indicative of saprobity, the maximum share belongs to the β-mesosaprobe species - 32 species (including 11 species of algae bacillariophytes and 10 species of chlorophytes indicative of saprobity).