Thalassiosira incerta I.V. Makarova in Bot. mater. otd. spor. rast. Bot. inst. AN SSSR 14: 50, pl. 1, figs 9-16. 1961.

Synonym.

Coscinodiscus bulla M.H. Hohn & Hellerman.

Morphological description.

The frustule is cylindrical, valves approximately flat, 21.4-27.8 μm in diameter, in the middle of a valve 5 processes are located, 4-5 marginal fultoportulae in 10 μm, situated on the valve margin (Fig. 4F). The rimoportula is short-necked with an elongated, compressed narrow lip usually perpendicular to the margin.

Ecology.

The species was recorded as planktonic in water bodies of different types, typical for eutrophic/hypertrophic and highly saprobic marine, brackish, and fresh waters. It is euryhaline and eurythermal, in addition to being known as an alkaliphilic taxon (Okhapkin et al. 2016). Thalassiosira incerta was named an invasive taxon for Russia ( Kaštovský 2010; Korneva 2014).

Distribution.

Thalassiosira incerta was recorded near Mykolaiv city in the Southern Bug River (Table 1). For Ukrainian territory, there are few records from reservoirs of the Dnipro River and some estuaries of the Black Sea and coastal waters near Crimea (Tsarenko et al. 2009).

This taxon is quite cosmopolitan, and distributed in the Boreal of Europe (Great Britain, Russia, Ukraine), Asia (Azerbaijan), North America (Canada, USA), Africa (Egypt); Aral, Black and Caspian Seas (Sims 1996; Kuo and Guo 2003; Okhapkin et al. 2016; Genkal et al. 2020).