The Berlin institute last week pointed to the strong growth of the algae species Prymnesium parvum, which can form a poison that is deadly to fish. It added this weekend that the poison was found in the waters of the Oder. Satellite images would also have shown that there is an enormous amount of algae.
The first tests on fish eggs with the Oderwater had also shown that deadly effect, Goldhammer said. It is therefore very likely that the fish mortality is due to the algae, although this has not yet been definitively proven.
The algae bloom is not a natural occurrence. The increased presence of salt is caused by humans. It is not clear where the salt comes from and other factors probably also play a role, such as the low water level and an increased water temperature.
Poles and Germans living near the river have been worried for days about the massive fish kill in the Oder. About 200 tons of dead fish have already been recovered from the river.