Phytoplankton as an indicator of the current ecological status of the Ob River

Olga P. Bazhenova,Larisa G. Kolesnichenko,Natalya N. Barsukova

doi:10.3897/abs.7.e79236

Abstract

The species composition, taxonomic structure, and the dominant complex of algae, and the distribution of phytoplankton abundance in the studied watercourse were identified based on data obtained for phytoplankton from the Ob River (from Tomsk to Salekhard) in summer 2019. Green algae (division Chlorophyta) make up the basis of the phytoplankton abundance in the river. The dominant complex is represented mainly by centric diatoms (genera Aula&#1089;oseira, Cyclotella, Stephanodiscus) and non-heterocyst forms of cyanoprokaryotes (genus Aphanocapsa). The numbers and biomass of phytoplankton gradually decrease downstream of the Ob River; below the confluence of the Irtysh River, the edge effect occurs: increase in the diversity and density of organisms at the boundaries of ecosystems. Compared to the previous studies, the proportion of green and euglena algae, and cyanoprokaryotes in the taxonomic spectrum of phytoplankton increased, the composition of the dominant complex enriched, including due to non-heterocyst forms of cyanoprokaryotes, and the trophic status of the river increased to the category of eutrophic waters.

Highlights

The Ob is one of the largest rivers in Western Siberia, Russia and the planet as a whole
The river is the most important transport artery of Western Siberia; its upper and middle reaches are occupied by large cities with developed industry, its basin is rich in oil, gas, and coal
Materials and methods The study employs data obtained in processing of 43 quantitative and 21 qualitative samples of phytoplankton from the Ob River taken along the route from the village of Melnikovo to the mouth of the Irtysh River (20 km below the confluence of the Irtysh) in July 2019, and near the city of Salekhard in the first decade of August (Fig. 1)

Summary

Introduction

The Ob is one of the largest rivers in Western Siberia, Russia and the planet as a whole. In terms of the basin size (2,990 thousand km2), it takes the first place in Russia, and in the water content, it is the third after the Yenisei and the Lena rivers. With respect to the nature of the valley and watercourse, the river is conventionally divided into 3 parts: the upper part stretches from the confluence of the Biya and the Katun to the Tom mouth (1,020 km), the middle part stretches from the Tom to the Irtysh mouth (1,500 km), and the lower part stretches from the Irtysh mouth to the Ob Bay (1,160 km) (Plaschev and Chekmarev 1967; Mitrofanova 2019; Yermolaeva et al 2021). The river is the most important transport artery of Western Siberia; its upper and middle reaches are occupied by large cities with developed industry, its basin is rich in oil, gas, and coal. The only artificial reservoir built in the upper reaches is the Novosibirsk reservoir (Long-term dynamics... 2014)

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