Posidonia Oceanica is a seegrass endemic to the Mediterranean Sea that belongs to the family Posidoniaceae . It forms underwater meadows with a remarkable ecologic significance, and constitutes the climax community of the Mediterranena Sea. Due to its important role in the protection of the coastline from erosion it is a specially protected species.
Posidonia hosts a large amount of animal and vegetable organisms which find in the meadows nourishment and shelter. It is considered as a reliable indicator of the quality of the coastline seawater.
The algae that remain at the shore of the beaches cannot be removed between the 1st of November and mid-March as they contribute to the protection of the dunes of the beaches. Once removed, they are collected during the summer months so that they can be brought back to the beaches on the 1st of November.
It has to be taken into account that its presence and its colour is not a sign of dirt, but the opposite: it reflects the good health of the beach and functions as a natural protective of the sand.
An interesting fact is that in 2006 a Posidonia plant of 8 km length was discovered in the Balearic Islands with a proximate age of 100, 000 years old. The identification of the plant was possible by means of genetic markers. The discovery was accidental as it is estimated that the meadow hosts one hundred million specimen of the same species. It is considered one of the largest and oldest living organisms in the world.