Process of Typha angustifolia L. Colonization by Algae of Various Ecological Groups in the River Section of the Kaniv Reservoir (the Dnieper River, Ukraine)

The paper deals with the processes of Typha angustifolia L. colonization by algae in the river section of the Kaniv Reservoir. At the end of the first week of exposure, the free surface of study plants was colonized by algae (primary colonization), the species richness of the newly formed community comprised 79 species and infraspecific taxa, and the biomass reached 0.192 mg/10 cm2. In the third week of exposure, phytoepiphyton biomass on study plants decreased significantly, however in the fourth week "recolonization" of the free patches took place. It has been shown that the daily flow velocity and water level fluctuations directly affect the processes of colonization. When water level is high and its fluctuations are insignificant, phytoplankton and phytoepiphyton on neighbor plants are the main sources of species immigration to phytoepiphyton on study plants, and when water level drops down abruptly, species mainly immigrate from microphytobenthos. The migration of typically plankton Aulacoseira italica to the surface of plant substrates can be considered as mass effect. A significant positive correlation was established between A. italica biomass in phytoepiphyton on study plants and its biomass in phytoplankton (r = 0.97, p = 0.007). No such correlation has been found for phytoepiphyton on background plants, because their phytoepiphyton communities had been forming for a longer time, with species sorting processes prevailing.