Dead fish in the Oder River near Schwedt, Germany, August 2022 dpa picture alliance/alamy
Blue-green algae, which killed hundreds of thousands of fish in the Oder river between Germany and Poland in 2022, could reappear this summer with devastating consequences, scientists warn. are doing.
Between July and August last year, about 360 tonnes of dead fish were hauled from the Oder River, which flows 840 kilometers along the German-Polish border. small primnesium.
The European Commission described it as “one of the greatest ecological disasters in recent European river history”.
small primnesium Usually found in brackish waters of estuaries. Scientists still don’t know how the flower got to the Gliwice Canal in Poland, a tributary of the Oder river hundreds of kilometers from the coast.
But seaweed is now in the water, and scientists fear that new flowers could bloom in the Oder and nearby rivers if the conditions are right.
“That’s one of the main concerns we have. Not only will it recur in this river, but it could also spread to other polluted rivers.” 2022 fish deaths in the Oder.
Due to the poor water quality of the river, we were offered an ‘ideal soup’. small primnesium flowering, Flea and his colleagues concluded.
The Oder was already suffering from excessive levels of nitrogen and phosphorus due to emissions from agricultural and wastewater sites. This is the nutrient that enables algae flower growth.
The problem was exacerbated by a heatwave and prolonged drought that lasted through July and August 2022, lowering water levels across rivers and concentrating pollution.
Later, the discharge of salty wastewater from industrial sites near the Gliwice Canal caused the salinity of the river to spike and algae to flourish. It’s unclear whether the discharge was illegal or within the limits allowed under the permit, Free says. Polish records show that at least 34 facilities in the Oder catchment are licensed to discharge saline waste.
According to the JRC report, poor communication between German and Polish authorities exacerbated ecological damage, and “late and incomplete” information exchange slowed response efforts.
A spokesman for Germany’s environment ministry said in a statement that authorities were notified of the incident on August 11, but that the fish had already washed up downstream within the border and died. It said it was being revised, adding: “In the future, it will be even clearer that events such as fish die-off, for example, will also result in timely cross-border warnings being issued.” Polish Waters, Poland’s national water management agency, has been contacted for comment.
The accident not only killed a large number of fish, but also severely affected invertebrate populations such as mussels and snails, said Dietrich Borchardt of Germany’s Helmholtz Center for Environmental Research. These filter feeders typically help control algae blooms, so when their numbers decline, he says, the river becomes more susceptible to another bloom this summer and in the future.
“I think the rivers are likely to be in a much more fragile state than they were last spring, with the loss of invertebrates, which are less noticeable than fish but certainly present,” says Borchart.
According to a study by Germany’s Leibniz Institute for Freshwater Ecology and Inland Fisheries, further blooms could threaten river ecosystems as research suggests that the river’s fish stocks have already halved since the first incident. It can devastate.
Institute’s Jan Koehler has just begun a study to investigate the impact small primnesium It affects the survival and efficiency of filter feeders like mussels. “We fear that reduced filtration activity will favor mass development in the future. primnesium’ he says.
Oders need to undergo “intensive care” to prevent further flowering, Free said, and urgent work is needed to tackle industrial pollution along rivers and reduce nutrient loads. The JRC recommends that authorities should be able to suspend industrial discharges of salt-containing waste if the risk of occurrence is high.
Others believe that major changes in regulations governing industrial wastewater will be needed to protect the health of rivers in the future, especially as European summers become hotter and drier under climate change. The testimony needs to be rewritten with climate change impacts in mind, Borchardt said. “We need to ask whether permits, for example for wastewater discharge, are sufficient in the context of climate change,” he says. “My guess is not.”
reference: JRC Publications Repository, DOI: 10.2760/067386
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