After the fish kill: The Oder is slowly recovering

AAgainst the background of the fish kill in the Oder, Foreign Minister Annalena Baerbock (Greens) has called for increased efforts to ensure that rivers are in good ecological condition. “We will have to rethink how we deal with our rivers,” said the Brandenburg member of the Bundestag on Thursday during a visit to Reitwein near Frankfurt an der Oder. The scale of the disaster is staggering.

The cause of the fish die-off, which has not yet been clarified, has led to considerable medium-term damage to the entire ecosystem, Baerbock said. The disaster was most likely caused by the combination of low water levels, high temperatures and discharges of sewage.

Climate change is forcing people and ecosystems to make adjustments, said Baerbock. The resilience of rivers must be strengthened. “For me, this is not just a German, but a European question. We have a shared responsibility for the river,” said the Greens politician. Water knows no borders. It is therefore crucial that Germany and Poland “not without, or even against, each other”, but jointly discuss the clarification of the environmental catastrophe and questions about the further use of the Oder.

Healthy fish species proven

Meanwhile, scientists have identified 19 healthy fish species in the Oder. According to the Institute for Inland Fisheries in Potsdam-Sacrow, the samples come from a stretch of river south of Frankfurt (Oder). The scientist Daniel Hühn told the German Press Agency that the 1,800 fish caught included everything from young fish to perennial fish.

Brandenburg’s Environment Minister Axel Vogel (Greens) said on Wednesday: “The acute crisis is over.” There have been “no dead fish recorded for a few days”. Even small water crabs that were released for control would no longer die.

According to data from the Brandenburg State Office for the Environment, the oxygen content and the pH value in the Oder are back to normal levels. Researchers had identified the so-called golden algae (Prymnesium parvum) in the river, which was able to grow, among other things, from the salt introduced and the toxin caused masses of fish to die. Scientists had detected both the alga and the toxin it produced in the river.

Algae bloom already at the beginning of August

According to the new findings of the scientists, an alga was already spreading near Wroclaw in Poland at the beginning of August. Evaluations of satellite data showed a sudden increase in chlorophyll concentrations in the entire course of the river from August 3rd to 4th, as the Leibniz Institute for Freshwater Ecology and Inland Fisheries announced on Thursday. These are considered indicators of algal blooms. These values ​​were also increased from July 19th to 20th.

Whether it is the so-called golden alga (Prymnesium parvum), which was detected by the scientists with data after August 6, cannot be said, said the aquatic ecologist at the institute, Christian Wolter, of the German Press Agency. “The satellite images do not differentiate between species. It could also have been other algae. You would need water samples from the area in question to be able to prove that.”

According to the researchers, it is not yet possible to conclusively assess whether the algal blooms in July and August are directly related. What is clearly recognizable, however, is the very rapid spread of the bloom that followed and which from August 10th covered almost the entire Oder.

According to the federal government, it is unclear when fishing will be possible again. Brandenburg is currently examining whether affected fishing companies can be compensated. As long as it has not been clarified what led to the death of fish in the Oder, no permission can be granted for fishing in the river, emphasized Brandenburg’s Consumer Protection Minister Ursula Nonnemacher (Greens). Further scientific studies would have to be awaited for this.