Brittany helpless in the face of the invasion of green algae

In Binic (Côtes-d’Armor), a tourist town of 7,000 inhabitants of the bay of Saint-Brieuc in Brittany, the situation is terrible on the five beaches. “Since 2009, we have never known such a year with so many strandings, laments the new unlabeled mayor, Paul Chauvin. The whole beach is covered, the beach is green. It’s been acres! “

And yet every morning since July, the city teams have been busy with construction machinery to collect these green algae because as they rot, they give off a foul odor and a potentially fatal gas.

“They remove everything they can. When they finish their collection, we have clean beaches. And then the next tide deposits algae again in the same day.”

Paul Chauvin, Mayor of Binic

to franceinfo

“From where an impression of work of titans, describes Paul Chauvin, and a total incomprehension of the inhabitants who come in the afternoon, see completely green beaches and ask what we do “. The observation is clear: since the beginning of the summer, 832 tonnes of green algae have been collected on the beaches of Binic, four times more than last year.

And other municipalities are obviously concerned such as Hillion, still near Saint-Brieuc where two beaches are currently closed.

Blame it on the weather. This year, it provided the perfect conditions for green algae to proliferate. “We arrived in April with the brightest spring we’ve had in years. Lots of sun, that’s a big growth at the start of the season., explains Sylvain Ballu, monitoring project manager at Ceva, the center for the study and valuation of algae. Normally she [l’algue] must start to stick my tongue out from the month of May or June, and there we had a resurgence with very intense rains. The equivalent of two and a half months of rain between June 15 and July 15. At that time, we give fertilizer to the green algae, which makes them grow again. “

According to the first data from CEVA, 2021 promises to be one of the record years in the Côtes d’Armor and northern Finistère. The areas covered by the layers of green algae could be at a level 50% higher than the average for nearly 20 years.

Green algae feed on nitrate. However, the agricultural world uses fertilizers rich in nitrate, part of which leaks to rivers and then to the sea. The rate has fallen in recent years because some farmers have changed their production method, but this is still not enough. To achieve this, the mayor of Binic believes that the state must support farmers much more. “This is what is not up to par today, which has not been able to bear fruit. We cannot ask professionals to embark on a path without having certainties of maintaining their returned.”

“The State promised them support that was not up to par. There are farmers who have committed to different productions who have still not received their subsidy.”

Paul Chauvin

to franceinfo

Faced with the problem, Paul Chauvin also had a motion voted on by his municipal council a month ago calling on the public authorities to assume their responsibilities, in particular with immediate measures to meet the challenges. “When there was in the past these phenomena of oil spill, the State immediately put in the means. We would like that for green tides, green algae there are the same means. The algae continue to proliferate on our sides and we do not care. It is unacceptable, it is disgust and anger “, the chosen one is in despair.

For his part, the Prefect of Brittany, Emmanuel Berthier, announced in September that the State would mobilize additional resources and notably propose “three-year contracts” to producers and agricultural cooperatives to encourage them to lower the nitrate level in the water. But changing farming methods could take years.

According to Sylvain Ballu, iThere are solutions, not to eradicate the problem, but at least to mitigate or help, such as, for example, new collection techniques. “For the moment, we only collect the algae which are in large bundles on the upper beach because they are the ones we manage to collect with public works tools, notes this monitoring project manager at Ceva.

“But with more suitable tools that will collect, for example, floating algae, we could try to target the periods when there is not much, suggests the researcher. We could help the system to get rid of its stocks by trying to remove biomass at key periods to avoid too much of it being present again in March-April when conditions become very favorable for growth. .

“It can be a way to get in the short term to remove some of the symptoms and maybe even to ensure that the green tide is not expressed in such a massive way as it is now.” For Sylvain Ballu, France is the European champion of green algae but other European countries are also affected such as the United Kingdom, Ireland and Italy.