Cyclotella atomus var. gracilis Genkal & K.T. Kiss in Hydrobiologia 269: 43, figs 10-16. 1993.

Morphological description.

The frustule is low-cylindrical, central part of valve is slightly tangentially undulated, valves 4.6-7 μm in diameter, and a clear boundary between regional and central zones is present, 15-20 wedge-shaped striae in 10 μm, with central process (Fig. 6D, E).

Ecology.

Planktonic in rivers, lakes, freshwater, eutraphentic (Hofmann et al. 2018). It is regarded as an euryhaline species (Kiss et al. 2012).

Distribution.

Cyclotella atomus var. gracilis is here first reported for the studied area, and was found at all investigated sites during this study (Table 1). In turn, its existence was reported in Dnipro waters (Maystrova et al. 2007), as well as for the Danube River (Genkal and Ivanov 1990).

This species is cosmopolitan, i.a. it was recorded for European waters (Kiss et al. 2012; Genkal et al. 2020).