MICROSCOPIC EXAMINATION AND 16S METABARCODING FOR COMPARATIVE ANALYSIS OF CYANOBACTERIA COMMUNITY STRUCTURE IN A PLAINLAND WATER STORAGE BASIN

Abstract

Light microscopy and 16S metabarcoding was used to determine the composition and structure of cyanobacteria community in a bay of a major plainland water storage basing and neighboring water area. Both methods suggest that the core of the community is formed by representatives of the families Aphanizomenonaceae, Prochlorococcaceae and Microcystistaceae, the dominant species belonging to the Aphanizomenon-Dolichospermum complex, which are typical for the initial stages of cyanobacteria blooming in the Volga water storage basins cascade. A satisfactory similarity between the dominant complex structures determined using the morphological and the molecular genetic approaches has been found at the family and order levels. There are however noticeable differences at the genus and species levels and among minor species. Despite that the identification of the operative taxonomic units (OTU) and reliably described cyanobacteria species was possible in far not every case, the values of variability indexes calculated using microscopy and metabarcoding data were similar and, thus, OTUs generally correspond to species distinguished morphologically. The causes of the discrepancy between the results obtained using the two methods are discussed, including peculiarities of OUT discrimination algorithms, differences copy numbers of the ribosomal operon and differences in chromosome numbers in the cells of cyanobacteria of different types. For of all these reasons, the number of sequences defined by metabarcoding is not a direct analogue of cells number or amount and thus should be regarded as an independent characteristic of a community.