Golden algae (“killer algae”) as a threat to Poland’s economy and nature

The unprecedented bloom of golden algae Prymnesium parvum in the Oder in 2022 has been the worst ecological disaster in Poland and Germany since decades. In 2023, the penetration of those “killer algae” from the Gliwice Canal, as well as from the Czernica and Januszkowice reservoirs into the mainstream of the Oder was stopped by the State Water Holding – Polish Waters. The article presents the current state of knowledge on this disaster and draws conclusions from pioneering tests conducted in Poland on methods to mitigate blooms in flowing waters (in the Gliwice Canal). Additionally, this work compiles and presents foreign methods of eradicating golden algae in fish ponds, in areas of great natural, sailing and fishing values, as well as fauna restoration (including mussels of family Unionidae, significant for both the economy and nature protection) following the massive bloom of P. parvum. Key words: golden algae, Prymnesium parvum, prymnesins, algal bloom, harmful algal bloom (HAB), ecological disaster, Oder, Gliwice Canal, oxbow lakes, CuSO4, H2O2, Phoslock, Lanthanum, La, coagulant PIX111, barley biostabiliser