The pieces of the puzzle are only slowly being put together as to how the massive fish kill in the Oder could have happened: researchers now have a microalgae with the name Prymnesium parvum in view, which is known to produce toxins under certain circumstances that are dangerous to fish. But there are still many unanswered questions. Including why the algae was suddenly able to multiply so much. Now there is evidence that a Polish ore mine discharged large volumes of highly saline water into the river.
»Prymnesium parvum is known for the occasional fish kill,” said the water ecologist Christian Wolter of the German Press Agency on Wednesday. The researcher at the Berlin Leibniz Institute for Freshwater Ecology and Inland Fisheries emphasized whether the algae actually 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.
Several striking changes in the water of the Oder
An algal bloom is a sudden, massive increase in algae or cyanobacteria in a body of water. As a result, the surface of the water turns green, sometimes blue or red, and the water becomes cloudy and “cloudy”. The cause is usually over-fertilization with phosphate or other nutrients. All of this matches the data from the measuring station for water quality in Frankfurt an der Oder. As the Science Media Center (SMC) writes, several noticeable changes were registered there on August 7, 2022: the oxygen content and turbidity of the water had increased significantly, the pH value and the amount of total chlorophyll had increased significantly, the absorption of UV light higher than normal. At the same time, the nitrate-nitrogen content dropped enormously and the electrical conductivity of the water shot up.