The Neptune grass, or Posidonia Oceanica - unlike what suggested by its name - is an endemic plant in the Mediterranean basin. It is not a seaweed, but a plant, consisting of ribbon-like leaves of bright green color, grouped in bundles, arranged in a fan shape, stems, flowers and rhizomes. Thanks to the photosynthesis it produces a large amount of organic substances, a source of food for many organisms, forming the starting point for a complex trophic net.

The Neptune grass areas play a key ecological role with respect to the coastal system. Neptune grass meadows are found on the seabed - up to 30-40 meters deep - and are an area of refuge for many marine species, giving rise to a complex food web. The Neptune grass play a key role in the containment and protection of coastlines from erosion caused by wave motion: they soften the force of the waves; its fallen leaves, transported by sea, and accumulated on the shore in winter, contrast the ´thinning’ of the shoreline by creating a natural barrier. In this way it becomes a new ecosystem that is home to organisms that feed on the life forms inhabiting the alive Neptune grass.

The posidonieto (Neptune grass area) is a priority habitat that is likely to disappear from the territory of the EU. The main factors that determine the degradation of meadows, in addition to the intrinsic fragility of this type of vegetation, are the wastes into the sea, the increased load of sediment, the phenomenon of trawling and installation of anchors.