Stephanodiscus hantzschii Grunow in Cleve and Grunow in Bih. Kongl. Sven. Vet. Akad. handl. 17(2): 115, pl. 7, fig. 131. 1880.

Synonyms.

Stephanodiscus hantzschianus Grunow, S. hantzschii var. delicatula A. Cleve, S. hantzschii var. zachariasii (Brun) Fricke, S. zachariasii Brun.

Concept synonym.

Cyclotella operculata sensu Hantzsch in Rabenhorst, Fl. Alg. Eur.: N 1104. 1861.

Morphological description.

The frustule is low-cylindrical, valves flat 13.6-21.4 μm in diameter, striae multiseriate with 6-7 in 10 μm, central processes are absent, spines large and pointy, growing from each rib (Fig. 5E).

Ecology.

Planktonic in lakes and rivers, indifferent, alkaliphilic, α-mesosaprobic, eutraphentic serving as an indicator of eutrophication in rivers, reservoirs, lakes worldwide mostly because of phosphorus loads ( Håkansson and Stoermer 1984; Van Dam et al. 1994; Burge and Edlund 2016; Hofmann et al. 2018).

Distribution.

Stephanodiscus hantzschii was identified for the Southern Bug River in Mykolaiv city and downstream (Table 1). It is widespread taxon in Ukrainian water bodies: the rivers Danube, Dnister, Southern Bug, Siverskyi Donets, Dnipro and its reservoirs, coastal waters.

It is a cosmopolitan species, known from Europe (Belarus, Bulgaria, Finland, France, Germany, Moldova, Norway, Romania Russia, Ukraine), Asia (Armenia, China, Georgia, Japan, Korea, Mongolia, Russia, Tadjikistan, Uzbekistan), North America (Canada, USA); Aral, Azov, Baltic, Black and Caspian Seas (Krammer and Lange-Bertalot 2000; Tsarenko et al. 2009; Genkal et al. 2020).