Posidonia

Posidonia: A Key Marine Plant in the Mediterranean

Posidonia: a key underwater plant in the Mediterranean ecosystem

Posidonia (Posidonia oceanica) is a flowering marine plant often mistaken for a seaweed. It is made up of bundles of leaves attached to rhizomes, underground stems that anchor themselves to the seabed.

It forms vast underwater meadows between the surface and 40 metres below the surface, particularly along the coast of southern Corsica. This species is endemic to the Mediterranean, meaning that it is found nowhere else.

Although it only covers 1 to 2% of the seabed, Posidonia plays a central role in Mediterranean biodiversity: its beds are home to almost 25% of the area's marine species.

A seagrass bed with multiple functions

The Posidonia meadow is a major indicator of the quality of the marine environment and contributes actively to the ecological balance of the coastline:

Natural habitat: it provides a refuge and breeding ground for numerous animal and plant species.

Environmental role: its sensitivity to pollution makes it a good indicator of the quality of coastal waters.

Protection against erosion: its rhizomes bind sediment, the leaves reduce the effects of swell, and the Posidonia banks (natural deposits on beaches) limit storm damage.