In the search for the cause of the mass deaths of fish in the Oder River, on the German-Polish border, researchers are keeping an eye on a toxic species of algae that has developed rapidly in the river. Meanwhile, the microalgae by the name Prymnesium parvum has been identified, water ecologist Christian Wolter said Wednesday. “The species is known to occasionally cause fish deaths.” However, it is unclear whether the algae toxin is the reason for the fish’s death.
The researcher at the Leibniz Institute for Freshwater Ecology and Inland Fisheries in Berlin emphasized whether toxins were produced in this case. He spoke of massive algal blooms at 200 micrograms per liter and over 100,000 cells per milliliter of water. However, algae toxin is harmless to humans.
Usually found in brackish water
The type of algae actually lives in brackish water, Wolter described. This typically occurs in estuaries where fresh and salt water mix. But in a saline environment, they can grow well, said the aquatic ecologist. In addition, algae need high pH values. “As a brackish water species, it would not otherwise form a mass development in the Oder.”
For the expert, there is a clear link between the introduction of salt and the development of algae. He personally doesn’t believe in an accident, Wolter said. Initially, several media outlets reported on the algae, including rbb and t-online.