Taxonomic diversity and structure of the under-ice phytoplankton in Lower Ob (March-April 2021)

Abstract

The subglacial phytoplankton of the Lower Ob was studied at three sites in the area of Salekhard in March -April 2021. 71 taxa of algae from Cyanobacteria, Chrysophyta, Bacillariophyta, Cryptophyta and Chlorophyta were identified with a predominance of diatoms (55 %), among which they were noted as true plankters (representatives of 5 genera), as well as those that live in benthos and fouling (15 genera). Aulacoseira granulata and Stephanodiscus hantzschii, as well as unknown small spherical and filamentous cyanobacteria, were found at every station and section. Among the surveyed sections, the maximum number of taxa was found at the section of the Malaya Ob (Azovy - 38), slightly less at the sections of the Bolshaya Ob (Kazym-Mys - 36 and Salemal -- 34). The number of algal divisions, on the contrary, was lower on Azovy than on Kazym-Mys and Salemal (four and five, respectively). An ecological and geographical analysis of the composition of winter phytoplankton showed that it was dominated by representatives of plankton in terms of habitat, cosmopolitans in terms of geographical confinement, indifferences in relation to the pH of the environment and alkaliphiles in relation to water salinity, as well as betamesosaprobionts in relation to the content of organic compounds.