This weekend, holidaymakers on the Basque coast had the unfortunate surprise of seeing the beaches closed.

The cause of the problem: a tiny algae the size of a seed, potentially toxic to humans.

While awaiting the results of the analysis laboratories, local elected officials are taking measures to monitor this new scourge.

REPORTAGE

On the Basque coast, swimming takes place under very close surveillance.

A potentially toxic algae appeared on the beaches of the coast this weekend.

Consequence of global warming: it normally evolves in much warmer waters.

Access to the sea was suspended from Sunday in Biarritz, Bidart and Saint-Jean-de-Luz before being authorized again by the Regional Health Agency on Monday at midday.

Several swimmers already have symptoms

This seaweed dispersed in the waves of the Basque coast is no bigger than a grain of watermelon.

It clings to the rocks, hides discreetly on the fine sand… but it leaves traces.

In Biarritz, brown and sticky clumps form on the surface of the water with, as a bonus, a foul odor.

What to frighten swimmers and other surfers, even to make them sick.

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Since Sunday, several vacationers have triggered symptoms: malaise, vomiting, flu-like condition or skin irritation ... And even if the analyzes show that this algae from tropical waters does not represent at this stage a serious danger for humans, the mayor of Biarritz, Maider Arostéguy, remains on alert.

"We are going to have an update every day with the ARS and the Pyrénées-Atlantiques prefecture," she says on Europe 1.

"Everything is done for the safety of swimmers"

To monitor the phenomenon, the town hall alerted rescuers so that they could "spot any packages of algae".

General practitioners are also in contact with the city to "report directly a possible increase in the number of cases".

"Everything is done for the safety of swimmers", assures Maider Arostéguy.

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Samples taken on the entire Basque coast, between Anglet and Hendaye, are being analyzed.

Faced with this threat of a new kind, the mayor of Biarritz insists: if the danger is proven, she will not hesitate to evacuate once again the beaches, crowded with people in this mid-summer.