In their search for the cause of the mass deaths of fish in the Oder, the researchers are also looking at a toxic species of algae that has developed rapidly in the river. In the meantime, the microalgae with the name Prymnesium parvum has been identified, said the water ecologist Christian Wolter of the German Press Agency on Wednesday. “The species is known to occasionally cause fish kills.”
It is still unclear whether the toxin of the algae is the reason for the fish deaths in the Oder. The researcher at the Berlin Leibniz Institute for Freshwater Ecology and Inland Fisheries emphasized whether it produced toxins in this case. He spoke of a massive algal bloom with 200 micrograms per liter and more than 100,000 cells per milliliter of water. However, the toxin of the algae is harmless to humans.
The type of algae actually lives in brackish water, Wolter described. This typically occurs at estuaries where fresh and salt water mix. But in a saline environment, they can grow well, said the aquatic ecologist. In addition, the algae need high pH values. “As a brackish water species, it would otherwise not form a mass development in the Oder”.
For the expert there is a clear connection between the introduction of salt and the development of algae. He personally does not believe in an accident, said Wolter. Initially, several media reported about the algae, including rbb and t-online.
The Brandenburg state government still assumes that the fish kills are not only due to natural causes. “We can safely rule that out, otherwise the high PH values ​​and the increased oxygen content and much more would not explain themselves,” said Prime Minister Dietmar Woidke (SPD) on Wednesday in Beelitz. You still don’t know what happened. “All we know is that something must have happened.”
At the same time, Woidke renewed his criticism of communication with the Polish side. “It is a fact that six days before fish died here, fish died in Poland – and we were not informed.” Therefore he is “deeply disappointed” by the Polish government. Due to international treaties, Poland would have been obliged to provide information at an early stage.
According to the head of government, in the search for the cause of the great fish kill, Brandenburg is also getting support from business and research institutions, including the chemical company BASF at the Schwarzheide site, the Brandenburg Technical University Cottbus-Senftenberg (BTU) and institutes that deal with water quality. “We have concentrated everything we know in the country on this task,” said Woidke. This is so important because all other questions depend on it – such as the time of the regeneration of the Oder, the fishing and the relief efforts to collect the fish to protect people’s health.
The Polish public prosecutor’s office has so far heard 228 witnesses as part of their investigation into possible causes. The investigators, together with witnesses, also made twelve site visits to different sections of the river, said Deputy Attorney General Krzysztof Sierak on Wednesday. “It is not clear from previous activities what caused the massive fish kill.”
