The oceanic posidonia is not an algae, but an aquatic plant, that is, it has a root, stem and leaves. It is endemic to the Mediterranean and its importance lies in the fact that it is a key element to preserve marine ecosystems, prevent the erosion of coasts and to balance the presence of CO2 in the sea and in the atmosphere. 
It forms underwater meadows that have a fundamental role in the conservation and protection of beaches and dunes, zones of great fragility and ecological value, since they form natural breakwaters that attenuate the action of the waves. On the beaches, the dead leaves form barriers against the effects of erosion caused by winter storms, and between temporary and temporary these dead leaves are buried under the new contributions of sand, trapping and thus settling the beach.
As if it were forests, posidonia is essential for the ecological balance of the marine environment; it cleans and oxygenates coastal waters and hosts a multitude of fish and invertebrate species, which is why it is considered a good bioindicator of the quality of coastal marine waters.


Its green leaves are long and flattened, being able to measure up to one and a half meters, forming large meadows on the seabed. The average life of their outbreaks is about 30 years. It blooms in autumn (although not always) and gives some fruits called “olives of the sea”, some balls that, after detaching from the plant, float to the shore where they usually appear between May and June. Its role in the ecosystem is very important since many species find their nutrients and their habitat

s in the posidonia, such as several species of starfish and numerous sea urchins, octopi, cuttlefish, shrimp, crabs and small fish. This plant represents for them a large pantry and a place to reproduce and for the young to develop.


Maritime works, the pollution of coastal waters, the generation of artificial beaches, the warming of sea waters due to climate change, the removal of dead leaves that reach the beaches and the anchorage of vessels seriously threaten Posidonia ecosystems . It is a very slow growing plant and is considered a non-renewable resource / system, so the loss of posidonia is almost irreversible. 
The oceanic posidonia meadows are disappearing throughout the Mediterranean Sea, which is recognized and included in the European Union’s Habitats Directive as a protected priority habitat. In Menorca, Posidonia is protected in several areas, such as Es Grau, where you can see first-hand the benefits of this “miraculous” plant.

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