Phytoplankton of the Flowing and Flow-regulated Stretches of the Ural River in Different Seasons

Abstract

Features of the seasonal changes in the number of species, biomass, and the ratio of taxonomic groups of phytoplankton of flowing and flow-regulated sectors of the Ural River are described. In the unregulated sector of the river, the maximal number of species was recorded in July, and in the upper and lower reaches of the reservoir – in October. The maximal biomass of phytoplankton in the unregulated sector of the river and in the lower zone of the reservoir was observed in the summer, and in the upper zone – in the spring. The influence of combining a number of parameters of the water bodies and environmental factors (typology, morphometry, flow velocity, the flow of substances from the catchment and from the higher sections, and temperature) on the quantitative characteristics of communities is discussed. The leading role of water temperature for the phytoplankton development in the unregulated sections of the river and the lower zone of the reservoir is shown, which are characterized by environmental conditions that impede the abundant development of phytoplankton: high flow rates, the late onset of biological spring, and low nutrient availability. The biomass values in the unregulated sections of the river correspond to β-mesotrophic – β-eutrophic waters, in the upper part of the reservoir – to β-mesotrophicones , and at the dam section – to α-βmesotrophic ones. According to the saprobity index, the entire investigated water area is characterized by β-mesosaprobic conditions.