In Belgrade, the Sava River has become covered with a thick layer of algae. According to Serbian scientists, such a large bloom is the result of high temperatures that persist in the city for most of the summer. Not only are the city's waters at risk, but also parks and gardens.
In early September, a section of the Sava River floodplain in Belgrade, the capital of Serbia, was covered with a thick green carpet. Boats and the swans broke through the thick layer of algae that tightly covered the water surface.
“This has never happened before”
As hydrologist Gordana Subakov Simic told Reuters, the particularly abundant bloom was fueled by high air temperatures and low rainfall. Belgrade has seen a record number of hot days and hot nights this summer. The warm water in the Sava provided an ideal environment for the algae.
– The amount of oxygen in the water decreases in direct proportion to the increase in water temperature. All these conditions are harmful to organisms inhabiting the riverbed, especially underwater plants – she explained.
Blossom on the Sava in BelgradePAP/EPA/ANDREJ CUKIC
The researcher noted that the drought also decimated urban vegetation. Unirrigated plants withered completely, and some trees in the Botanical Garden cracked. “This has never happened before. We are cutting down trees, and climate change will cause even greater destruction of our flora,” she said.
Another problem in the Sava is the over-fertilization of water. Municipal sewage that flows into the river is not treated sufficiently. Polluted waters are full of organic matter and minerals, which makes them an excellent breeding ground for algae and accelerates their multiplication. This process occurs particularly easily in slowly flowing water in backwaters, which is not driven by the main stream of the river, which prevents water mixing and sewage dilution.
Main image source: PAP/EPA/ANDREJ CUKIC