Algae flora of the Lower Irtysh and its tributary, the Tobol River

The results of algoflora studying the Lower Irtysh and its tributary, the Tobol River, are presented. A total of 432 taxa of species and subspecies ranks were identified from 124 of 58 families and 8 departments. For the first time, a systematic list of algae is given. The greatest species and intraspecific richness were characterized by green, diatoms, blue-green (cyanoprokaryotes) and euglenic algae (93 % of the total list). Planktonic species, cosmopolitan species and beta-mesosaprobes predominated. In the phytoplankton of the mouth of the Irtysh, 368 algae taxa with a rank below the genus were registered, in the modern period in the lower reaches - 247, in the Tobol River - 192. The algae of the Lower Irtysh plankton were distinguished by a large variety of green algae and an abundance of diatoms, in the Tobol River -cyanoprokaryotes (August). The estuary section of the Irtysh River was distinguished by the highest level of quantitative development of phytoplankton, diatomaceous plankton. The modern period is characterized by the development of small-cell green algae, diatom-chlorococcal plankton. A high level of development of summer algocenosis caused by the vegetation of cyanoprokaryotes and green algae was observed in the Tobol River. The appearance of cryptomonads in the 2000s indicates organic pollution of the water masses of the surveyed rivers. The obtained materials have a certain scientific and practical value and can be used in biomonitoring.