Poland is fighting to stop the spread of toxic golden algae

Polish authorities have recovered more than four metric tons of dead fish from a tributary of the Oder River in recent days. So far, the fish die-off has been limited to a section of the Gliwice Canal, a spokeswoman for the local water authority told the radio station Tok.fm.

The cause is a bloom of toxic golden algae, the authority reported. Currently, regular patrols on the water and on land are monitoring the situation, and the dead fish are being removed from the affected section of the canal. The operation of two locks has also been suspended until further notice. The goal is to prevent the golden algae from spreading to other sections of the canal. If this proves unsuccessful, the water authority is considering the controlled release of hydrogen peroxide, which destroys the cells of the golden algae.

Fish Die-off in the Summer of 2022

In the summer of 2022, a mass fish die-off occurred in the Oder River. Experts in Germany and Poland concluded that the fish deaths were most likely caused by the toxic effects of a bloom of the poisonous golden algae Prymnesium parvum.

The Gleiwitz Canal, which opened in 1939, is 41 kilometers long and connects the Upper Silesian city of Gleiwitz (Gliwice) with the Oder River. Most recently, a large number of dead fish were recovered there again in the summer of 2024. At that time, the authorities ordered the water to be oxygenated and introduced hydrogen peroxide.