Diversity and Transformation of the Community of Planktonic Freshwater Protists in the Estuarine Tributary Zone of a Large Plainland Reservoir: Metabarcoding of the 18S Ribosomal RNA Gene

• Published in: Biology bulletin of the Russian Academy of Sciences 2023-08, Vol.50 (4), p.707-723
• Main Authors: Umanskaya, M. V., Gorbunov, M. Yu, Bykova, S. V., Tarasova, N. G.
• Format: Article
• Language: English
• Subjects: Alveolata; Biochemistry; Biogeography; Biomedical and Life Sciences; Cell Biology; Ecology; Life Sciences; Next-generation sequencing; Plankton; rRNA 18S; Zoology
• ISSN: 1062-3590; 1608-3059
• DOI: 10.1134/S1062359022602804

— The first data on the composition and diversity of the summer community of planktonic protists in Usinsky Bay and the adjacent water area of the Kuybyshev Reservoir, obtained using high-throughput sequencing of the 18S ribosomal RNA gene, are presented. In the composition of the protist community, 1150 operational taxonomic units (OTU) were found; among them, representatives of the Stramenopiles–Alveolata–Rhizaria (SAR) supergroup predominate. In the complete library, Stramenopiles predominate by the number of OTU, represented (in descending order) by Chrysophyceae (8.5%), Opalozoa (8.3%), Diatomea (4.7%), and Oomycetes (Peronosporomycetes) (3.7%); by the number of nucleotide sequences, Alveolata (62.0%) and, first of all, Ciliata (56.9%). There are four interconnected communities of protists: of the river area, the bay itself, the mouth zone, and the reservoir outside the influence of the bay (above the mouth). The communities of the river area and the reservoir area above the mouth have the greatest contrast in composition. In general, the estuarine system studied has features of both ecocline and ecotone. The competitive relationships with cyanobacteria have the main effect on the development of the phototrophic component of eukaryotic plankton. Cyanobacterial “bloom” also affects the structure of the heterotrophic part of the community, although this effect is less pronounced. The development of Archaeplastida, Rhizaria, and minor groups of protists positively correlates with the portion of Metazoa sequences in the samples, which reflects the intensity of the metazooplankton press. Sequences belonging to Bolidophyceae and Rhodelphida, the taxa rare for freshwater, were found. These findings expand the biogeography of these groups that were found so far in very few freshwater reservoirs.