Assessing the ecological state of a small river in the urbanized area in terms of phytoplankton, zooplankton and zoobenthos characteristics (the Sodema River of Vologda Oblast as a case study)

Abstract

During the studies (2021–2022) of the Sodema River (Vologda Oblast), a total of 125 species and forms of phytoplankton, 74 species of zooplankton and 70 species of zoobenthos were identified. Above the city of Vologda, the riverine phytoplankton was not abundant (0.2 mln cells/l, 0.3 g/m3 ); diatoms dominated. Zooplankton and zoobenthos in the upper river reaches were most diverse. Zooplankton number was very high (7.1 thous. ind./m3 , 0.5 g/m3 ). Upstream, the river was assessed as mesotrophic, clean and β-mesosaprobic. Within the city of Vologda, phytoplankton diversity and abundance of cyanobacteria, euglena and cryptophyte algae increased, while species richness of zooplankton and zoobenthos sharply declined. Zooplankton number was low (0.8 thous. ind./ m3 , 10 mg/m3 ). In zoobenthos, oligochaetes developed en masse. Low reaches of the Sodema were characterized as eutrophic, hypereutrophic and β-α-mesosaprobic. River pollution greatly affected zoobenthos because of pollutants accumulation in soil.

Keywords

• vologda city
• bioindication
• aquatic organisms
• saprobity
• water quality