Hydrogen peroxide, a chemical previously associated with hair bleaching, was pumped into the Kudnitsa River, a tributary of the Oder, to stop the return of golden algae – also known as Prymnesium parvum – which was once again killing tons of fish.
Poland is not alone in facing this challenge. According to Research published last year in the scientific journal NatureAlgal blooms around the world have increased significantly in frequency and intensity.
What are algae blooms and why do they occur?
Algae are microscopic organisms found in oceans, lakes and rivers. They are essential to aquatic ecosystems. However, when their blooms get out of control, some species – such as those found in the Oder and Kłodnica rivers – produce toxins that can be harmful to fish, humans and other elements of the ecosystem.
Algal blooms are caused by a combination of environmental factors, including warmer temperatures, more light, and increased nutrients in the water from agricultural waste and sewage systems. Some research suggests that algal blooms are likely to increase as temperatures rise due to climate change.
However, the 2022 Audra fish kill has been dubbed a “man-made environmental disaster,” with scientists finding that the main factor causing the golden algae bloom was the high salinity of the water caused by discharge from coal mines and other industries into the river.
Parmenium does not produce visible flowers. The first sign that something is wrong may be a crazed or dead fish.
What impact can hydrogen peroxide have on the environment?
According to the Polish Ministry of Climate and Environment, hydrogen peroxide has killed 90% of the golden algae at the junction of the Gliwice and Kłodnica canals.
This is not the first time this bleach has been used to combat microorganisms: its effectiveness was also proven in 2017. British testsHowever, according to Christian Wolter, a scientist at the Leibniz Institute for Aquatic Ecology and Inland Fisheries in Berlin (Leibniz Institute for Freshwater Ecology and Inland Fisheries)It was first used by Polish authorities in the river, not in still water.
The lesser of two evils?
The impact of the chemical on the environment is not yet fully understood, says Jacek Engel, head of the Green Mind Foundation, a Polish environmental NGO. Engel adds that his colleagues are researching the effects of hydrogen peroxide on other parts of the ecosystem, such as plankton, tiny organisms that are a major food source in water bodies.
In his opinion, the local impact on the ecosystem that the use of this chemical could have must be weighed against the greater evil that could be the spread of golden algae, “because of course it will not just kill Parmencium parvum. It kills everything… but it still kills the organisms in one specific place to save the entire Oder ecosystem,” explains Walter.
Walter added that Polish authorities have set up several monitoring points to measure how quickly hydrogen peroxide disappears and its impact on invertebrates, algae and fish.
As Elisabeth Varga, a scientist at the University of Veterinary Medicine in Vienna, explains, in order to avoid harming other organisms, it is necessary to get the right concentration of the chemical. “You have to find a concentration that is high enough to destroy the microalgae and prevent their growth, but not so high that it affects all the other animals,” she points out.
According to British research, hydrogen peroxide decomposes after a short period and soon becomes harmless. Tests also showed that “fish and large invertebrates were not harmed by the experiment.”
“mutation management”
“Hydrogen peroxide is a temporary measure,” says Juliusz Konczow, an ecotoxicologist from Greenpeace Germany. “But this is not a solution to the problem we are facing in the Odra River.” The Polish Ministry of Climate Change has also confirmed that the use of hydrogen peroxide is a measure to be used in crisis situations. According to the German toxicologist, the main solution would be to lower the current threshold values of wastewater discharged into the river by coal mines and other companies, as this significantly increases the salinity of the water.
It removes the effects, not the causes.
Walter believes that using hydrogen peroxide is an example of combating the symptoms, but it is not the root of the problem. – We know that Primnesium parvum is a brackish aquatic algae, and the main reason for its presence in the Oder is its salt content.
According to research by Greenpeace Polska published last year, many tributaries of the Oder, which receive wastewater from numerous hard coal mines, have water salinity higher than the Baltic Sea. Environmentalists described this finding as “shocking” because the Oder is a freshwater river while the Baltic Sea is a saltwater sea.
“I would say that the situation is similar to what we saw last year, and in some points worse than in 2022,” says Konczow, referring to the level of salt in the river. The Polish government has already announced plans to build desalination plants to improve the water quality of the Odra River.
Environmentalists: Leave the Odder to Nature
But the German environmental group BUND and other organizations in Poland argue that protecting the Oder should go beyond measures to control and stop salt discharge, and include keeping it as wild as possible, rather than treating it as a waterway for barges and tourist traffic.
There are many EU regulations on rivers, says Walter. “The problem is their implementation.” This applies not only to Poland, but also to other member states. Wolter says that 60% of rivers across Europe are not in good ecological condition, adding that most German rivers do not meet the goals of the EU’s Water Framework Directive, which was designed to improve water quality in European water bodies.
while International Commission for the Protection of the Oder River from Pollution – A joint agreement between the Czech Republic, Germany and Poland – has become more involved in monitoring the river since the disaster in 2022, and could be allowed to take more action, Walter believes.
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