L’archipel des Glénan et ses fonds de maërl : un trésor marin de Bretagne
What makes this archipelago so fascinating are its rich and varied marine resources, especially the maerl beds, a unique and fragile marine habitat. The Glénan archipelago, located in the heart of Brittany, is a natural treasure trove that attracts lovers of the sea and biodiversity. This collection of islands, often referred to as the “paradisiacal islands” of Brittany, is famous for its turquoise waters and its landscapes to keep you cool.
The maërl: a unique marine habitat
The maërl is a red calcareous algae that develops on the marine fonds. It is mainly composed of several species of calcareous algae, including lithothamnium. These algae, which have been developing for millions of years, form submarine banks that are among the most ancient living habitats known. The maerl is particularly present in the Glénan archipelago, where it plays a crucial role in the marine ecosystem.
One can observe three main maërl gisements around the Glénan: one extending from Concarneau to the tip of Trévignon, a second to the north of the island of the Moutons, and a third to the north of the archipelago. The bancs de maërl to the north of the île des moutons and the large bancs de Concarneau à Trévignon are bancs de maërl vivants en surface, while those to the north of the archipelago are mainly composed of maërl mort.
An exceptional biodiversity
The fauna and flora associated with the maerl are exceptionally rich. Around 800 species of animals and more than 100 species of algae can live and reproduce there, making this habitat one of the richest in terms of marine biodiversity. The species there are protected from super predators, which allows this ecosystem to thrive.
The maerl provides a shelter and a source of nourishment for many marine species. It also contributes to the clarity of the waters of the archipelago, as its composition contributes to the whiteness of the sable. This characteristic attracts many plongeurs and snorkelling enthusiasts who admire the beauty of the Glénan’s underwater world.
La protection du maërl
Due to its fragility and ecological importance, the maerl is protected by strict environmental regulations. The exploitation of the maerl has been prohibited since 2011 in the Glénan archipelago to protect this unique habitat. This measure aims to limit the impact of human activities, such as dragging, which can damage these beds.
Conservation efforts are essential to maintain biodiversity and the ecological functions associated with these marine ecosystems. The French Ministry responsible for the environment emphasises the importance of finding substitutes for oil, such as calcareous marine sediments and coquilles of marine molluscs, to reduce the pressure on these fragile habitats.
The Glénan archipelago: a Natura 2000 site
In 2004, the islands of the Glénan archipelago were classified as a Natura 2000 site, recognising their importance for the conservation of biodiversity. This classification aims to protect natural habitats and species of plants and birds threatened with extinction in Europe. In 2007, the initial perimeter of the site was extended to the sea in order to also protect marine birds and mammals, as well as the richness of marine life, including the maerl beds.
The Natura 2000 site now covers around 500 km² of marine and island habitats, offering enhanced protection to this unique ecosystem. The zostères, the laminar forests and the maerl beds are just some of the marine habitats that benefit from this protection.
Visiting the Glénan, we are reminded of the importance of protecting these fragile ecosystems for future generations. The beauty and richness of this archipelago are a testimony to the need to protect our natural heritage so that everyone can benefit from and enjoy the splendour of nature.
