Centric diatom diversity in the lower part of the Southern Bug river (Ukraine): the transitional zone at Mykolaiv city Author Bilous, Olena P. https://orcid.org/0000-0001-5229-3667 Institute of Hydrobiology, NAS of Ukraine, 12 Geroyiv Stalingrada Ave., Kiyv 04210, Ukraine bilous_olena@ukr.net Author Genkal, Sergey I. I. D. Papanin Institute for Biology of Inland Waters of RAS, Settle Borok, Nekouz District, Yaroslavl Region 152742, Russia Author Zimmermann, Jonas Botanischer Garten und Botanisches Museum Berlin, Freie Universitaet Berlin, Koenigin-Luise Str. 6 - 8, Berlin 14195, Germany Author Kusber, Wolf-Henning Botanischer Garten und Botanisches Museum Berlin, Freie Universitaet Berlin, Koenigin-Luise Str. 6 - 8, Berlin 14195, Germany Author Jahn, Regine Botanischer Garten und Botanisches Museum Berlin, Freie Universitaet Berlin, Koenigin-Luise Str. 6 - 8, Berlin 14195, Germany text PhytoKeys 2021 2021-05-20 178 31 69 http://dx.doi.org/10.3897/phytokeys.178.64426 journal article http://dx.doi.org/10.3897/phytokeys.178.64426 1314-2003-178-31 286CBEFF513C55E1B66F6224758AC2F6 Melosira subglobosa (Grunow) Houk, Klee & Tanaka in Fottea 17 (Supplement):17, pl. 17, figs 1-10; Pl. 19, figs 1-15; pl. 19, figs 1-11. 2017. Synonyms. Melosira borreri var. subglobosa Grunow, Melosira moniliformis var. subglobosa (Grunow) Hustedt. Morphological description. Frustule shape is cylindrical to approximately octagonal (Fig. 2A, F ). Valve 12.5-26 μm in diameter, mantle height 3.1-8.5 μm . Valve face nearly octagonal with flat tops (Fig. 2B-E, G ). Girdle with puncta forming straight and transverse rows 32-56 in 10 μm . Figure 2. SEM ( A-D, H ) and LM ( E-G ) images of species found in the transitional zone at Mykolaiv city: A-G Melosira subglobosa ( A, F girdle views, B-E, G , valve views) H Melosira varians , partial valve view and girdle view of complete frustule. Scale bars: 10 μm ( A-C, E-H ); 20 μm ( D ). Ecology. Marine and brackish, benthic-planktonic (tychoplanktonic) species, halophilic, widely distributed. Indicates significant organic pollution (eutrophication), α-mesosaprobiont ( Kolpacov et al. 2014 ). This species prefers water enriched with dissolved organic matter, and is capable to switch from autotrophic to heterotrophic or mixed type of nutrition ( Andreeva et al. 2008 ). Additionally, these diatoms are ubiquitous, and widely distributed in seas and estuaries of temperate zones in habitats with a moderate level with increased level of human impact ( Kuzminova and Rudneva 2005 ; Ryabushko 2009 ). Distribution. Melosira subglobosa is one of the most common species at the sampling sites near the Mykolaiv area in the Southern Bug River (Table 1 ). For Ukrainian territory, it is known from the coastal zone in the northwestern part of the Black Sea, Crimean seaboard, and some estuaries. For a worldwide distribution, it was recorded from coastal zones of Europe, and Asia; specifically, from Lake Aral, Baltic, Bering, Black, Caspian, Mediterranean, North and Norway Seas ( Tsarenko et al. 2009 ).