Free-living ciliates during the period of the greatest cyanobacterial water bloom in the Usinsky bay (Kuibyshev reservoir)

The study of free-living ciliates in the Usinsky bay (the Kuibyshev reservoir) during the period of mass development of cyanobacteria are presented. The diversity of the ciliate species structure and spatial distribution were studied in summer. The abundance of ciliates varied from 124 to 1176 103 ind./m3, biomass - from 6.9 mg/m3 to 104.9 mg/m3 during the study period. No significant differences in the communities of ciliates in different ecotopes of the bay (riverbed, open and overgrown by macrophytes coastal areas) were found. However, on average, in the riverbed part, all indicators of species richness and diversity, and quantitative development were higher than in the littoral zone. The massive development of representatives of s/cl. Peritrichia (up to 51 % of abundance and 66 % of biomass): single cells species associated with planktonic algae (genera Vorticella, Vaginicola), and colonial free-floating Epistylis procumbens Zacharias, 1897, was the distinctive feature of ciliate community in the Usinsky Bay during the period of greatest cyanobacterial bloom. Water bloom significantly changed the trophic structure of the ciliate community: the role of algophages and nonselective omnivores, ordinary trophic groups of the Reservoir was significantly reduced, and bacterio-detritophages became absolutely dominated. It was shown that the dominant species of cyanobacteria had a significant effect on the ciliate community during the cyanobacterial water bloom.