After having spread well beyond the historic sites of the bay of Saint-Brieuc and bay of Lannion in the 1990s, the green algae blooms seem to have peaked in 2009. The extent of the problem meant that the government had to take emergency measures integrating the implementation of the ‘green algae plan’. Specifically, the goal of this plan was to reduce by 40% the nitrogen fluxes that fed into the eight most affected bays, primarily located on the northern and western coastlines of the peninsula. Besides the imbalances caused within ecosystems, the eutrophication of coastal waters can have significant economic impacts. In the case of Brittany, it was estimated that it cost more than one million euros to collect and put to good use the 2009 green algae alone. The losses incurred, especially in terms of tourist activities, also need to be taken into account.
The mixed results of the actions taken can be partly explained by the inertia of the environment. As a result, given the slow response time of hydrosystems to changes in practices, the measures undertaken must be carried out over the long term in order to truly restore Breton aquatic environments.