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Dead fish are removed from the Oder river in Poland (pictured August 15)
Photo: Lisi Niesner / REUTERS
Toxic substances produced by algae could be the cause of the massive death of fish in the Oder - from the point of view of the Leibniz Institute for Aquatic Ecology, corresponding indications are increasing.
The strong growth of the alga, which actually thrives in brackish water, is in turn due to a salt input into the river, said researcher Tobias Goldhammer of the dpa.
»That is our currently most likely hypothesis.«
Last week, the Berlin institute pointed out the strong growth of the algae species Prymnesium parvum, which can form a poison that is deadly for fish.
At the weekend it was also said that this poison had actually been detected in the water of the Oder.
In addition, satellite data would have shown a massive algal bloom in the Oder.
Algal blooms are not natural events
Initial tests on fish eggs with the Oder water have now confirmed the deadly effect, said Goldhammer.
"In the chain of evidence, it is very likely that this algal bloom is the cause of this fish kill." However, this has not yet been definitively proven.
It is also important that the algal bloom is not a natural event, but is due to human influences, namely the increased salt load in the river water.
It is currently not possible to prove where the salt came from.
Other factors also likely played a role, including low water and increased water temperature, Goldhammer said.
Meanwhile, the dispute between Poland and Germany continues.
The federal government has rejected Polish allegations in connection with the fish kill.
"We regret that the Polish side came to this assessment," said a spokesman for the Federal Ministry for the Environment on Monday in Berlin, referring to the accusation from Warsaw that Germany was spreading "fake news".
The search for the causes of the fish kill in the Oder is still not complete.
Poland's government has also complained that German authorities have only set up a few oil barriers to catch the masses of fish that have died in the Oder.
"This really raises the question of why we have already been able to erect 29 oil booms on the Polish side, in which fish are caught, while only three such barriers have been erected on the German side, despite our requests," said Deputy Foreign Minister Szymon Szynkowski vel Sek on Monday the public broadcaster Polskie Radio.
The Polish fire brigade is also willing to borrow these barriers or set them up on the German side.
Boom booms are deployed in the river to catch and recover dead fish before they drift further downstream.
ani/dpa
