Background: Many investigations on phytoplankton from the Nakdong River carried out. However, since the weirs were constructed, only changes in phytoplankton biomass and dominant species have been restrictively studied in phytoplankton investigations in the Nakdong River. Added to this, any investigation on the phytoplankton flora has not been done in the Nakdong River. The aim of this study is to elucidate the characteristics of phytoplankton communities in the Nakdong River with the weirs built in it.
Results: We observed a total of 103 taxa of Euglenophytes belonging to 8 genera from middle-lower part of the Nakdong River. The genus Trachelomonas was the most abundant group making up 40 taxa, followed Lepocinclis (20), Phacus (17), Strombomonas (14), Euglena (5), Colacium (3), Monomorphina (3) and Menoideum (1). Among them, a total of 22 taxa including Colacium (1), Lepocinclis (8), Phacus (4), Strombomonas (4) and Trachelomonas (5) were reported for the first time in Korea, and 86 taxa including those new to Korea were first recorded in the Nakdong River. All the species are illustrated with photomicrographs, and new to Korean species briefly discussed with regard to their taxonomy together with photomicrographs.
Conclusions: The present study, a total of 22 taxa including one species of Colacium, 8 taxa of Lepocinclis, 4 taxa of Phacus, 4 taxa of Strombomonas and 5 taxa of Trachelomonas were reported for the first time in Korea, and 86 taxa including those new to Korea were first recorded in the Nakdong River.

Keywords: Euglenophytes, phytoplankton diversity, Nakdong River, photomicrographs