Changes in Phytoplankton of the Irpin River (Ukraine) as a Result of Military Activities in Its Basin

Abstract

Phytoplankton structure was studied in a comparative aspect (before and after the beginning of military activities) in the section of the Irpin River belonging to a large lowland rivers flowing in silicate rocks. On the whole, 132 algal species of seven divisions were found in the water column of the Irpin River during the period of investigations. Bacillariophyta and Chlorophyta were highly diverse in their species composition (37.1 and 31.1% of the total number of species). The distribution of plankton algae at the studied stations even within the same massif of surface waters was non-uniform in terms of species composition (the Sorensen coefficient of community similarity on the average was 37%), species richness (18-49 species), cell numbers (1930 thousand cells/L - 24,450 thousand cells/L), and biomass (2.118 mg/L - 20.374 mg/L). Almost different algal species dominated at various stations (14 species among 20 dominated only at one station). Compared to the previous period of investigations (2018), the number of plankton algal species in the studied section of the Irpin River somewhat increased (from 121 to 132). Phytoplankton taxonomic structure also somewhat changed. The contribution of Bacillariophyta increased from 22.3 to 37.1% and that of Cyanoprokaryota - from 9.1 to 12.1%. In this case, the contribution of Chlorophyta decreased from 47.1 to 37.1%. The quantitative indices of phytoplankton development increased. The maximum numbers increased from 19,480 thousand cells/L to 24,450 thousand cells/L, whereas the maximum biomass - from 5.143 mg/L to 20.374 mg/L. As a consequence of the impact of military activities on phytoplankton of the Irpin River, it is possible to consider an increase in the number of its species, the maximum numbers and biomass, as well as the contribution of water bloom forming blue-green algae in the estuarine section of the Irpin River due to the disturbance of hydromorphology and the income of an additional amount of nutrients from flooded territories, which can lead to the formation of such a negative phenomenon as water bloom in this section of the river.