Epiphyton of a cascade plain reservoir under different hydrodynamic conditions

Abstract The paper deals with the study of the influence of hydrodynamic factors (current, water level fluctuations, and wind driven wave) on the structure of epiphyton occurring on macrophytes of various ecological groups in the Kanev Reservoir (the Dnieper River, Ukraine). The reservoir is subdivided into the river and lake sections, including the transit and non-transit zones. It has been found that the main factors inhibiting the development of epiphyton in the main riverbed of the river section include high current velocities conditioned by discharge currents and water level fluctuations, in the bays of the river section – water level fluctuations, whereas in the transit zone of the lake section – wind driven wave. The performed investigations have shown that the increase in water movement conditioned by high current velocities, water level fluctuations, and wind driven wave results in the decrease in epiphyton species richness, in changes in its species composition, taxonomic structure, dominant complex, dimensional structure, and its numbers and biomass structure, and also in the decrease in the quantitative indices of its development. It has been found that the average number of species in a sample and epiphyton numbers and biomass depended inversely on current velocity, water level fluctuations, and wind driven wave. As a consequence, the increase in water movement can result in the lower oxygen release and organic matter production by this community, and the decrease of nutrient uptake and pollutants accumulation, thus limiting the role of epiphyton in water bodies self-purification. At the same time, it has been shown that water movement variously influenced algal communities occurring on the substrates of different types, including epiphyton found on macrophytes and periphyton registered on solid artificial inorganic substrates.The obtained data can be used in predicting the ecological state of the designed water bodies.