German experts consider the massive spread of a toxic alga to be the most likely cause of the massive fish kill found in the Oder in summer 2022. This emerges from a report by a national group of experts headed by the Federal Environment Agency, which the Federal Environment Ministry has published. The researchers thus confirm the previously suspected assumptions about the causes of the environmental catastrophe.
The analysis comes to the conclusion that introduced salt contributes to the mass proliferation of brackish water algae Prymnesium parvum have led. This in turn produced a toxic substance that led to the massive death of the fish and other organisms such as snails and mussels. According to the report, the researchers could not identify the cause of the salt discharge. The exact source of the salts, other elements and chemicals is unclear, it says.
Overall, the analyzes indicated “multi-causal mechanisms of action” that would have led to the massive deaths of the animals. High temperatures and low levels of precipitation have exacerbated the situation because the concentration of harmful substances has risen as a result. The experts also identified herbicides that were “highly likely to be industrial discharges.” The acute poisoning cannot be derived from this, it said.
The analysis of more than 1200 known substances and elements showed that the substances detected “typically came from discharges from industrial or municipal sewage treatment plants”. The report does not give any further details.
In order to prevent future disasters of this kind, the scientists recommend, among other things, further research into the spread of brackish water algae and improvement of the cross-border warning and reporting system. Existing permits for the discharge of substances into water should also be reviewed.
The massive fish kill was discovered on August 9th on the German side of the border river. According to government information, Polish authorities had the first indications of this at the end of July. Germany accused Poland of not reporting the events early. A German-Polish group of experts set up in mid-August did not submit a joint report. Instead, there are now two separate analyzes of the respective pages. Polish experts had presented their findings the day before and also identified the spread of the algae as the most likely cause of the fish kill.