Primary production of phytoplankton of the river Ob and the estuaries of its large tributaries in the site from the lower point of the Novosibirsk hydraulic system to the Novosondrovo (2022, 2023)

Abstract

An assessment of the state of the river ecosystem was carried out. Ob based on the characteristics of the gross primary production of phytoplankton and BOD5 in the area from the lower pool of the Novosibirsk hydroelectric complex to the village. Novosondrovo (below the mouth of the Chulym River). The study was conducted in July 2022 and 2023. on the targets. The determination of gross primary production of phytoplankton was carried out using the flask method in oxygen modification in situ. At the same time, we determined the mineralization, transparency and temperature of water, pH, the content of oxygen dissolved in water, and the concentration of easily oxidized organic substances (BOD5) in the river. Ob and the mouth areas of Tom and Chulym. It was shown that the obtained values of the average gross primary production of Ob phytoplankton were significantly higher than in the summer low-water period in the Ob Bay and the upper reaches of the river. Yenisei. Particularly high rates were noted in areas subject to anthropogenic load and off the coast with a well-developed floodplain. The influence of tributaries on the functioning of Ob phytoplankton is shown. The key abiotic factors for the functioning of phytoplankton have been identified. It was revealed that, in terms of gross primary production and BOD5, the trophic status of the Ob and its tributaries during the studied period ranged from mesotrophic to polytrophic waters. The highest level of trophicity in 2022 was noted in local areas in the area of large settlements, in 2023 — in a more significant section of the Ob from the village. Dubrovino to the village. Krivosheino and at the mouth of the Tom, decreasing downstream the Ob to a mesotrophic level. It was noted that the trophic status of the Ob has increased significantly over the past 20 years, which may be a consequence of the increased anthropogenic load on the watercourse.