This scanning electron microscopy study of phytoepiphyton, collected in 2016–2018 from the reservoirs system of the Dnieper River (Kiev, Kremenchug, Dneprodzerzhynsk, Zaporozhzhia (Dnieper), Kakhovka) and the Lower Dnieper, has revealed 133 species of diatom algae, represented by 138 intraspecific taxa from 43 genera, 22 families, 13 orders and 3 classes. A total of 14 species and 1 variety of Bacillariophyta from the genera Achnanthidium Kȕtzing , Amphora Ehrenberg, Cymbella Agardh, Encyonema Kȕtzing, Gomphonema Ehrenberg, Halamphora (P.T.Cleve) Levkov, Navicula Bory, Nitzschia Hassall are new for the flora of Ukraine. Short diagnoses, synonymy, ecological characteristics and distribution data, as well as original micrographs are presented for these species. The majority of these pennate diatoms from periphyton of higher aquatic plants are freshwater, widespread species. Among the species new for the flora of Ukraine, recorded in phytoepiphyton from the reservoirs system of the Dnieper River and the Lower Dnieper, two are freshwater-brackish species (Halamphora thermalis (Hustedt) Levkov и Navicula vekhovii Lange-Bertalot et Genkal). Besides, and Navicula cf. vaneei Lange-Bertalot can vegetate in waterbodies with medium-high mineralization and Halamphora cf. subholsatica (Krammer) Levkov develops in mesohaline waters. Seven forms from the genera Amphora, Aneumastus D.G.Mann et Stickle, Cymbella, Gomphonema, Nitzschia, Ulnaria Compére have been identified to the genus. The largest number of new species and interesting forms of pennate diatom algae has been recorded in Kremenchug and Kaniv reservoirs as well as in the Dnieper reservoir. The species new for Ukraine belong to the class Bacillariophyceae and the algae identified to the genus – to the classes Bacillariophyceae and Fragilariophyceae. A hypothesis has been proposed that centric small-celled planktonic forms of diatom algae have a faster response to increasing salinity of Dnieper water than the pennate forms which develop in phytoperiphyton. That is because phytoepiphyton is a more inert algocenosis than plankton.
Keywords: Bacillariophyta, Dnieper reservoirs, phytoepiphyton, pennate forms, scanning electron microscopy, Ukraine