Massive occurrence of the alien invasive species Pleodorina indica (Volvocales, Chlorophyta) in a reservoir located in urban areas of Central Poland

Pleodorina indica (Iyengar) H. Nozaki is a rare species from the Volvocaceae family (Chlorophyta, Volvocales), which naturally occurs in aquatic ecosystems of the tropical climate zones. This is the first record of this species I in Poland in a flow-through man-made reservoir on the Olechówka River in Łódź. The sampling site of P. indica in Łódź is the northernmost site in Europe. Among other records, the species has been also reported from Austria in 1996 and the Czech Republic in 2003. During the summer of 2015, abundant occurrence of this species was observed at the sampling site, at extremely high air and water temperatures. Physical parameters in the reservoir and the duration of the P. indica bloom were measured. In addition, morphological features of the species were observed with the use of light and confocal microscopy.