The chlorophyta plankton of the Ob river nearby Surgut

The work is devoted to the study of the Middle Ob River Chlorophyta plankton (Khanty-Mansi Autonomous Okrug). Previous studies of the Ob River phytoplankton were carried out by Yu. V. Naumenko 30 years ago. The work aim is to assess the species composition and abundance of the Ob River Chlorophyta plankton developing nearby Surgut. Phytoplankton material was collected during the growing season of 2018 nearby Surgut. Research has been by accepted methods conducted. Light microscopy was used for identification, relevant keys and modern international nomenclature changes were used. A Chlorophyta plankton characteristic is given for the studied section of the river: species composition, systematic of the detected species, varieties and forms, characteristics of Classes, Families and Genera. Of 89 identified Algae species, 32 are mentioned for the first time. The Ob River phytoplankton is characterized by autochthonous development with the presence of a large number of single-species Families and Genera characteristic of boreal flora. Two peaks were identified in the development of Chlorophyta cell numbers: in July and September. 6 Algae species have floristically significance in the studied cenosis. Ecologically, planktonic, cosmopolitan species, indifferent to salts and pH value, predominate. According to the saprobiological characteristics, a large proportion of the detected Algae is included in the β-mezosaprobic and α-β-mezosaprobic zones.