SINOPSIS

Results of the study of seasonal changes in the content of the dissolved and suspended forms of silicon in the water of the Kanev Reservoir (the upper section, Obolon Bay) and their dependence on the development of diatoms are discussed in the paper. The concentration of the dissolved silicon accounted for 1.0−6.8 mg/L, whereas that of the suspended silicon − 0.05−0.4 mg/L. During the period of investigations, the contribution of diatoms to the total number of species accounted for 33%, whereas their contribution to the total biomass of phytoplankton was 63%. It has been found that the increase in their biomass in May − June was accompanied by a decrease in the concentration of the dissolved silicon, and also in the increase in the content of its suspended form. The distribution of silicon among the abiotic and biotic components of suspended matter of the studied water body was investigated. It has been found that during the period of diatoms vegetation a relative content of biogenic silicon in the composition of suspended matter increased up to 42−45%, whereas its minimal values (1−2%) were observed in wintertime.