Out of control phenomenon? Cyanobacteria pollution in lakes and rivers at record levels

You've probably heard of them before. Cyanobacteria are the very origin of life on Earth. However, if present in excessive quantities, this organism in water can be fatal to flora, fish, and pets . They are also called "blue-green algae."

And humans are not immune to this threat either, as it can cause nausea, headaches, and even breathing difficulties. The topic is being discussed because since the beginning of the year, 330 natural sites have already detected or suspected the massive presence of cyanobacteria, according to an environmental association.

"We're heading towards a record year," its president worried on RMC. Locally, some elected officials are also beginning to worry about the impact of bathing area closures on tourism .

And what scientists are noticing is the speed at which cyanobacteria are proliferating. “It's happening even faster than I could have imagined,” warns a scientist specializing in these microbes. Citing the example of Limousin, where in 40 years, the cyanobacteria rate has increased from 3% in contaminated bathing areas to 80% today.

According to the Occitanie Regional Health Agency , several factors favor their proliferation: nutrients, water temperature, sunshine, precipitation, high turbidity (water cloudiness) and the lack of predators.

But intensive agriculture and the discharge of more or less well-treated wastewater also play a role in the proliferation. They supply bodies of water with phosphorus, the main food of cyanobacteria.

This situation could even worsen with global warming. According to some scientists, rising temperatures could further promote the proliferation of these bacteria.