Bloom-forming and abundant dinoflagellates in thirteen reservoirs in Bulgaria (2018-2020)

Abstract

Thе present paper reports on 34 cases of blooms (21) and abundance (13) of 8 taxa from 6 genera of the class Dinophyceae in thirteen reservoirs in Bulgaria during the summer- early autumn periods of 2018-2020. During the blooms, biomass of dinoflagellates reached the maximum value of 93.3% in the Lenovo reservoir (Ceratium hirundinella in September 2019), while the lowest contribution was 25.2% in the reservoir Svezhen (Gymnodinium cf. uberrimum in August 2020). The contribution of abundant dinoflagellates ranged between 5% in the reservoir Aheloy (Ceratium furcoides in August 2020) and 18.5% in the reservoir Trakiets (Ceratium hirundinella in July 2020). Two of the quantitatively important species, Peridinium bipes and Apocalathium cf. aciculiferum, found as dominant in the reservoirs Aheloy, Radnevo and Tyurkmen, are known as potential toxin producers.