Fish decomposing in Oder river after mass death event sparks pollution risk

Warsaw, Aug 17 (EFE).- The decomposition of thousands of dead fish and shellfish in the Oder river is threatening Poland’s second longest waterway which has been seriously polluted by the mysterious mass die-off, an expert warned Efe in an interview.

“The secondary effect of tissue decomposition is the release of hydrogen sulfites and ammonia that are toxic and can dilute in water but also pass into the air,” professor Robert Czerniawski, a hydrobiologist at the University of Szczecin, told Efe.

The toxic spill can constitute a risk for animals and humans and the decomposition of fish and shellfish can become a food source for algae, which can reproduce at great speed and limit the volume of oxygen in the water, the expert warned.

The first signs of the mass fish deaths were detected near Olawa (west) in mid-July, but until last week the Polish government downplayed the incident, which has also appeared on the German side of the river.

On Sunday, the Polish interior ministry reported that it had deployed 2,500 police and firefighters to remove the evidence of the environmental catastrophe, predominantly dead fish and other animals.

The commander of the fire service on Wednesday said that 80 tons of dead fish have been removed from the Oder since Friday.

Czerniawski, who is currently conducting field research in the river, told Efe that compared to last week, there were fewer dead fish on the banks but that many may have sunk to the bottom of the riverbed and are yet to float to the surface.

“Much of the effects of the catastrophe have yet to be seen, and will be felt for months and even years,” he added.

The exact cause of the phenomenon is unknown.

Initial probes carried out by the authorities of the German region of Brandenburg, bordering Poland, detected traces of mercury, prompting rumors a toxic spill from a Polish industrial plant could have been the trigger.

High levels of salinization have been identified in the water, which amid the ongoing drought could also have precipitated the die-off.

Czerniawski suspects a chain reaction caused by a toxic substance and the consequent death and decomposition of a certain number of fish could be taking place.

“I don’t think that a single substance can cause such a massive death. This is rather a sequel to the whole process,” he said.

What is clear is that the catastrophe is of human origin, the hydrobiologist concluded.EFE


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