Three tons of dead fish in the Gliwice Canal. The services are sounding the alarm
Three tons of dead fish were fished out of the Gliwice Canal. The reason is toxic golden algae, and the services have introduced further bans.
About three tons of dead fish have been caught from the Gliwice Canal since Saturday, informed Polish Waters in Gliwice. On Wednesday alone, 947 kg of fish were removed from the 6th section of the canal, mainly bream, carp and crucian carp. No dead fish were found in other sections of the waterway. However, the services regularly check the canal and Dzierżno Duże.
The golden algae attacked. The concentration was 547 million cells
The direct cause of fish deaths is the golden algae, Prymnesium parvum. On Monday, its concentration in section VI of the Gliwice Canal was 547 million cells per liter of water.
Blooms of this algae can produce toxins that are dangerous to branch-eating organisms. Scientists identified the golden alga as the direct cause of the ecological disaster on the Oder in 2022. It also led to a mass fish kill in Dzierżno Duży in 2024.
Ban on using the Gliwice Canal. What must you not do?
The Silesian Voivode, Marek Wójcik, introduced a ban on using the 6th section of the Gliwice Canal. You are not allowed to enter the water there, swim, fish or eat fish. The ban also covers watering animals, watering, water sports and other activities requiring direct contact with water.
Polish Waters also banned navigation in section V. As explained, waves caused by the movement of vessels could lead to water containing golden algae entering Dzierżno Duży. The water flow from sections V and VI has been stopped. After rainfall and an increase in water level, the weir gates connecting the canal with the reservoir were also raised. This is intended to retain more water and limit the uncontrolled flow to Dzierżno Duże.
The services declare that they are ready to use hydrogen peroxide. During the experiment in Kłodnica in 2024, the substance reduced the number of golden algae by over 90%. There was no negative impact of the appropriately selected concentration on the flora and fauna of the river.
Why does golden algae grow in the Gliwice Canal?
The development of algae is favored by stagnation and heating of water during hot weather and its high salinity. According to the findings of the Supreme Audit Office, mines in the Silesian Voivodeship introduced an average of 183 million cubic meters of mine water annually into the Odra and Vistula river basins in 2020-2023. This meant approximately 1.5 million tons of chlorides and sulphates per year.
