EAccording to researchers, a type of toxic algae is responsible for the death of fish in the Oder. “There is no doubt that this toxin has been detected in all water samples, and in significant quantities,” said fish ecologist Christian Wolter of the FAZ on Monday. His colleague Elisabeth Varga from the University of Vienna specializes in the algae species Prymnesium parvum, which was detected in the Oder a few days ago. According to the researcher at the Leibniz Institute for Freshwater Ecology and Inland Fisheries, you have detected the poison. It is now necessary to research which subspecies it is and how effective the poison is under which conditions.
The algae does not necessarily develop toxins. According to researcher Varga, when this specific type of algae is present in very large amounts, a high concentration of the toxin occurs. Satellite images had confirmed a massive bloom of algae in the Oder on Saturday. Among other things, the poison attacks the gills of the fish, suffocating them. Which organisms could be affected in addition to fish and molluscs has not yet been finally clarified, nor is the danger to humans.
However, the researchers do not assume a purely natural cause. “This can happen more often if we continue to act irresponsibly,” said Wolter, referring to discharges and dams in the Oder. The proven type of algae needs saline water that is stagnant if possible in order to multiply. The electrical conductivity of the water, an indicator of salts in the water, had risen sharply at the Frankfurt (Oder) measuring point around August 7th. Between July 29 and August 10, a Polish company discharged large quantities of salt water from a retention basin into the Oder river near Głogów (Glogau) – with official approval. This may have exacerbated fish kills previously detected 170 kilometers upstream in Oława.
New fish kill near Stettin
According to Wolter, it is also possible that there is no direct connection between the two cases. There are currently problems in many rivers, not just in the Oder. According to the expert, non-toxic freshwater algae can also pose a threat to fish. As an alga grows, it uses up the nutrients in the water and then collapses. Bacteria decompose the algae, consuming oxygen in the process. There is then a massive lack of oxygen in the water locally, which can cause fish to die.
Polish media reported at the weekend about a new fish kill south of Szczecin in Siadło Dolne. The reason is a lack of oxygen in the river, said Michał Ruczyński, spokesman for the West Pomeranian Voivodeship, of the “Gazeta Wyborcza”. It was initially unclear what caused the lack of oxygen. In the part of the Oder that borders Mecklenburg-Western Pomerania, the water parameters are still unremarkable. “It doesn’t affect us yet,” said a spokeswoman on Monday.
