Due to rising temperatures, rivers in Central Europe and America are holding less and less oxygen. This causes danger to the fish.
Oxygen levels in rivers in Central Europe and America are rapidly decreasing due to rising temperatures. This causes danger to the fish. Environmental scientist Li Li The University of Pennsylvania and his colleagues analyzed the oxygen and temperature levels of 796 rivers in the United States and Central Europe. They used measurement data from 1981 to 2019 obtained from various sources.
There is no database containing all relevant measurements of rivers. Therefore, Li and his colleagues had to combine different data sources to create a comprehensive daily dataset for hundreds of rivers. They looked at water temperature, oxygen levels, weather information and information about local soils. The results were published in the journal Natural climate change.
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Using their dataset, the researchers developed Machine learningThe model, a type of artificial intelligence, can calculate daily oxygen and temperature levels for 796 rivers.
Researchers found that 87 percent of rivers have warmed over the past four decades. It was also revealed that 70 percent of the rivers are now low in oxygen. “For any liquid, the ability to hold gases decreases as the liquid heats up,” says Li.
Urban rivers warmed considerably during this period. Nevertheless, rivers near agricultural areas lost oxygen rapidly. “I think agricultural rivers have more nutrients that consume oxygen,” Li says. These nutrients can end up in rivers through fertilizers spread on agricultural land.
Fish in danger
Loss of oxygen in rivers endangers fish. “When the oxygen level drops to a certain level, they suffocate,” says Li. Healthy rivers typically have dissolved oxygen levels above 8 milligrams per liter. Rivers below 3 milligrams per liter are considered hypoxic, they contain very little oxygen and pose a serious risk to fish.
The researchers used their model to predict the temperature and oxygen content of rivers up to the year 2100. They found that if temperatures rise by 2.7 degrees Celsius, rivers will lose oxygen 1.6 times faster. For example, the Brooker Creek River in Florida now has about 204 hypoxia days per year. Li and his colleagues’ model predicts this number will increase by 5.7 days per decade.
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