The toll is getting heavier for this environmental disaster.
After an initial assessment of 100 tons of fish, the German government announced that it was finally 300 tons of dead fish that were extracted from the Oder.
"The Oder is currently the scene of an environmental disaster that will damage this precious ecosystem for a long time," German Environment Minister Steffi Lemke told The Pioneer news portal.
At the origin of this fatal disaster, the proliferation of a microalgae, also called “golden algae”.
The poisonous substance is common in estuaries and normally thrives in brackish waters with less salt content than the sea.
Chemicals may have played a role
If it was able to proliferate to such an extent in the fresh waters of the Oder, this indicates an abnormal salinity of the river, which could have industrial causes.
The precise causes of these mass disappearances remain to be determined, recalled the German environmental minister.
The disaster somewhat strained relations between Berlin and Warsaw.
Germany has thus accused Poland of having delayed informing it of the extent of the pollution.
Both sides suspected early on that chemicals played a role.
The Polish Minister of the Environment, Anna Moskwa, however, later clarified “that none of the samples tested so far” had “shown toxic substances”.
Of these 300 tonnes, approximately 100 tonnes were taken from the German side, in the Brandenburg region.
Dead fish are incinerated in specialized factories.
The first reports of mass fish kills in the Oder came from Polish locals and anglers as early as July 28.
In recent years, the Oder was known to be a relatively clean river, with around 40 species of fish living there.
