Breton beaches known for postcard views have acquired a far darker reputation, and Marta Zaraska of the Guardian traces how a slime problem turned lethal—and political. The culprit is vast mats of green seaweed, Ulva armoricana, fed by decades of intensive farming and nitrate runoff. When the algae piles up and rots, it can trap hydrogen sulfide gas at levels high enough to kill. That danger was long treated as theoretical. Then came a string of disturbing collapses involving joggers, tractor drivers, wild boar, and even a horse found in or near thick seaweed beds.
The article follows one family's 10-year fight to prove that 50-year-old runner Jean-René Auffray didn't simply suffer a heart attack in 2016. His wife, Rosy, initially buried him without an autopsy after authorities appeared uninterested in investigating further. But later testing at the estuary where he collapsed found hydrogen sulfide levels shooting off the scale after investigators pierced crusted seaweed beds. In 2025, a French appeals court finally ruled that toxic gas from the decaying algae killed him and found the state mostly responsible for failing to control nitrate pollution.
Yet the area's intensive livestock system remains largely intact despite years of lawsuits and government "seaweed plans." Farmers argue they are being unfairly blamed, while environmental advocates say officials have focused more on cleaning beaches than stopping pollution at its source. France is now on its third seaweed action plan, but a court recently called the measures inadequate. Meanwhile, the algae keeps spreading along Brittany's famous coastline. Read the full story.
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