Conservationists say that toxic seaweed has now spread to more than 200 sites along the Atlantic coast from southern Brittany to the beaches of Normandy.
Bays popular with Britons from La Baule, a top summer beach destination in southern Brittany, to Granville in the Cotentin are now struggling to dispose of thousands of tons of Ulva lactuca – more commonly known as sea lettuce.
Experts have warned that the algae poses a health risk as when it rots it produces hydrogen sylphide, which if trapped under a seaweed crust and suddenly released can prove as deadly as cyanide.
Anses, the French Agency for Food, Environmental and Occupational Health and Safety, has just issued guidelines for dealing with the green sludge, saying it must be picked up within 48 hours of reaching the beach before it can start producing gas. If not, in the worst cases, it can cause "loss of consciousness with cardiac arrest or coma".
The seaweed has been multiplying abnormally fast due to the use of huge amounts of nitrates in intensive pig and poultry farming that seep into the region's rivers and water tables and end up in the sea. Source