Health Impacts:Â Â Â Â Â As algae decompose, they release hydrogen sulfide (HS), a toxic gas. Severe cases of intoxication, and even animal deaths, have been reported, raising increasing public health concerns.
Solutions Implemented and Their Results:
1. Agricultural Regulations: Reducing Nitrate Inputs
Since the 1990s, France has implemented several plans to reduce nitrate inputs into Brittany's rivers:
The EU Nitrates Directive (1991): This directive imposes strict limits on the use of nitrogen-based fertilizers. Vulnerable zones in Brittany are subject to strict rules to prevent nitrate runoff into rivers.
The Green Algae Action Plans (PLAV): Launched in 2010, these plans include specific measures such as reducing livestock density, creating vegetative buffer zones along rivers, and managing livestock effluents.
Results: Â Â Â
According to a report by the Loire-Brittany Water Agency (2022), average nitrate concentrations in Brittany's rivers decreased by 20% between 2000 and 2020, dropping from around 50 mg/L to 40 mg/L in critical areas. However, these levels remain above the EU threshold of 25 mg/L needed to prevent eutrophication.
Limits:
Farmers face high costs to adapt their practices, which slows compliance.
The effects of these measures, while visible, remain insufficient to completely eradicate green algae blooms.
2. Collecting and Treating Green Algae
