Cyanobacteria are bacteria present in the fresh water of certain rivers or swimming pools in the region. When they proliferate, they can present a danger to human and animal health.
These bacteria can sometimes grow in rivers and bodies of water. This phenomenon is not alarming but when their presence is significant, cyanobacteria can produce toxins presenting a risk to human and animal health. In some cases they can form a green efflorescence on the surface of the water, or attach to stones and form green/brown biofilms*, which can break off (floc*), float and accumulate on the edges. of banks.
What are cyanobacteria?
Cyanobacteria are called cyanophyceae, cyan (blue) and phyceae (algae), because they have a blue pigment. They are also called “blue-green algae”. Several factors favor their proliferation: nutrients, water temperature, sunlight, water turbidity, lack of predators, etc. Their number can become extremely high (several billion cells per liter of water) and impact the appearance of the water.
How to manage the risk of cyanobacteria?
Daily monitoring of the presence of characteristic foam or foam is carried out by the person in charge of the bathing site. Cyanobacteria in bodies of water (planktonic) are searched for on swimming sites for which it has been highlighted, in the swimming profile, a possibility of development of these micro-algae or in the presence of foam, moss or biofilm.
To avoid risks, it is important to know the common sense precautions to implement. Recognizing the symptoms of poisoning also allows you to adapt your behavior
In 2023, in Occitaniamonitoring has been put in place at all freshwater swimming sites.
6 sites had to be temporarily closed following threshold values being exceeded. On 7 other sites, the vigilance level was reached, information to the public was carried out. We will also note a progressive presence of floc on the Tarn from the end of June, until a generalization over the entire Tarn from the beginning of August, impacting the sites of this watercourse. Public information was reinforced by targeted displays.
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