Not chemical waste, but toxic substances that excrete algae were the cause of massive fish deaths in the Oder. That is what the German research agency IGB suspects based on measurements in the river on the border with Poland. However, that does not mean that the fish died of natural causes, the researchers write.
The algae species Prymnesium parvum, which produces strong toxins, is common in the water, according to the researchers, although they have yet to confirm this with DNA research. It is remarkable that this alga lives in brackish water, between fresh and salty water, which normally does not occur in the affected part of the Oder. A combination of warm low tides from drought and industrial salt discharges may have created the conditions for the toxic alga to thrive.
At the end of July, thousands of dead fish were floating in the Oder. At that time, discharges of chemical substances, such as the poisonous mesitylene, were soon thought of. German politicians asked for clarification from Poland, which only shared information sparsely. The research by the Leibniz Institute for Freshwater Ecology and Inland Fisheries (IGB) is still ongoing, but due to all the public attention, the research institute is now coming up with preliminary results.
Also read the question: Massive fish kill in the Oder, but what’s the culprit?