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It’s the return of green algae in Brittany, a rather rare phenomenon at this time of year, even if it already happened five years ago. In the bay of Saint-Brieuc, a beach completely invaded by these algae has been prohibited to the public for seven months, so how can this proliferation be explained?
Closing a beach is the last resort. That of the Hôtellerie, in the nature reserve of Saint-Brieuc (Côtes-d’Armor), has remained desperately prohibited since last July. The green alga, also called sea lettuce, proliferates, swarms, even in the middle of winter, because of the mild weather conditions, shallow water and a sheltered bay. The danger arises when these green algae decompose, releasing hydrogen sulphide, a gas with the smell of rotten eggs, which in high concentrations can prove fatal.
The current situation has mobilized environmental defense associations. For local residents, it has been exasperation for too many years. The heart of the problem of green algae would be the intensive practice of agriculture. Industrial farms, as in the pig industry, release a lot of nitrate into the soil and waterways. The efforts of some farmers have led to progress and the envelope allocated by the State to fight against the phenomenon has increased from 5 to 10 million euros.