Invisible to the naked eye, l’Ostreopsis is an algae that can be toxic to humans, and which proliferates in theoretically warm and calm waters, near rocky coastlines. Although it has been known since the 1970s in the Mediterranean, this one appeared “consequentially on the Basque coast in summer 2021”we can read on the website of the urban community of Pays Basque. Its main route of exposure is the inhalation of sea spray. Indeed, according to the National Agency for Food and Health Safety (ANSES), “You only need to be a few meters from the sea to be intoxicated.” As revealed by France 3 Nouvelle Aquitaine, this marine algae is back, and led to the closure of the Port Vieux de Biarritz on July 21 following reports made by swimmers.
What is this hard-to-detect toxic algae?
According to ANSES, “Ostreopsis can accumulate on the water surface to form blooms.” Water blooms, which can create brown patches that can reach several square meters. However, “these can disappear quickly and it is not because they are not visible that there is no risk”. This is why ANSES emphasizes in its press release from last year that the only distinctive sign of the presence of the micro-algae is the sensation of a metallic taste in the mouth, even if it has only been inhaled and not ingested. A distinctive sign that had been reported by bathers at the Port Vieux beach in Biarritz. Indeed, the head of beaches at the Biarritz town hall, Jean-Philippe Oustalet, stated in the columns of France 3 Nouvelle Aquitaine that “Swimming people arrived at the viewpoint: they complained to the lifeguards about having breathing problems and reported that the water had a metallic taste”. This is why, as a precautionary measure, the closure of the beach has been decided.
Ostreopsis poisoning: what are the symptoms?
According to the website of the Basque Country urban community, “People exposed to the microalgae Ostreopsis, through swimming or inhalation of sea spray, may experience various symptoms,” such as :
- cough or sore throat ;
- runny nose and eyes;
- nosebleeds;
- breathing difficulties;
- fever, tremors and muscle pain;
- of the headachenausea;
- or even skin rashes.
Symptoms that can occur within 6 hours after exposure, even occasional, and which generally disappear within 3 to 4 days, without complications. As Carole Catastini, who coordinated the expertise, explains in a press release from Anses, these are: “People with respiratory problems are at greatest risk of developing symptoms. Therefore, they should avoid being near the coast when there is an Ostreopsis bloom.” As a reminder, More than 900 cases of poisoning on the Basque coast have been reported since 2021. Therefore, it is also advisable to wash your body and hair after swimming in the ocean, so as not to let this seaweed ruin your vacation.
“If it gets really hot in the next few days, there is a risk of algae blooms and we could potentially relive what we experienced in 2021,” said Doctor Guillaume Barucq, a doctor in Biarritz, to France 3 Nouvelle Aquitaine.
Sources :
- Preventing Ostreopsis poisoning on the Basque coast – the National Agency for Food and Health Safety (ANSES) – June 20, 2023
- Monitoring of the Ostreopsis algae – Basque Country urban community –
- Closed beaches, difficulty breathing: the toxic microalgae ostreopsis could well ruin your vacation on the Basque coast – France 3 Nouvelle Aquitaine – July 22, 2024
