Discovery of Unruhdinium penardii var. robustum in Saratov and Volgograd Reservoirs (Volga River, Russia)

A novel variety of dinophyte algae Unruhdinium penardii var. robustum (Qi Zhang, G.X. Liu & Z.Y. Hu) Gottschling in Gottschling & al., 2017 (=Peridiniopsis penardii var. robusta Qi Zhang, G.X. Liu & Z.Y. Hu) has been detected for the first time in Russia. It was found in two reservoirs of the Lower Volga, Saratov and Volgograd, in late August-early September 2020. Its abundance varied from 500 to 4500 cells/L; biomass was from 0.008 to 0.071 mg/L. The length of cells varied from 29 to 40 mu m, and the width varied from 24 to 31 mu m.