how violent thunderstorms cause “fecal” pollution on the beaches

In summer, the bathing is an affordable leisure that pleases as many people as possible. Except that sometimes, after putting on the jersey and swollen the buoys, the bad news graves: the beach is closed.

This is the bad news that the inhabitants of Saint-Cyprien (Pyrénées-Orientales) had this Monday, July 21, 2025: The Lagune beach is closed due to an abnormal control of the Regional Health Agency (ARS), reports News Perpignan.

In the Var too, all the swimming sites in the city of Hyères have been closed, reports ACTU VAR.

And that comes as the South, like a good part of France, was struck by violent thunderstorms this weekend. Because yes, the two information has a report.

Bacteria of fecal origin

As the BAUNDE.SANT.GOUV.fr site recalls, dedicated to the quality of bathing water, the latter are regularly controlled by regional health agencies, whether freshwater or seawater sites.

If there are several factors which can justify a degradation of the quality of the water, one of them results directly from the heavy rain. This is the microbiological pollution. “Essentially of fecal origin”, this happens when wastewater is found in bathing waters.

Rain can also cause overflows of wastewater collection and treatment works or significant streams on soiled surfaces.

Which is not completely without risk for bathers, who can contract ” pathologies the oto-rhino laryngeal sphere, the digestive system (gastroenteritis) or eyes ”.

In Canet-en-Roussillon, in mid-June, the beach was closed because of this, reports News Perpignan: “A momentarily high rate ofIntestinal enterococcius Justified the swimming ban for two days. As Public Health France recalls, enterococci “are commensal bacteria of digestive flora hospital infections managers rare and not very severe ”.

This July 21, the municipality of Martigues (Bouches-du-Rhône) had thus decided to prevent its beaches preventively because “the rain threshold recorded” was too high and, faced with the risk of pollution, the city firm its beaches preventively, recalls Marseille news.

Pollution linked (indirectly) to global warming

However, it is not just microbiological pollution that can close a bathing site. And heavy rains are not the only climatic events either.

For example, the temperature increaseand the sunshine rate have an impact on the development ofMicroscopic algae whether in fresh waters or in sea water.

Beyond “coloring water”, these algae can have an impact on health, especially in fresh water, where algae can release toxins“Variable nature and intensity, such as acute gastroenteritis, even neurological damage”.

On the sea side, the toxicity of algae mainly concerns the shells which then become unfit for consumption.

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