Posidonia is not a species of algae but a flowering plant, one which plays a huge role in the Mediterranean ecosystem. It is native to the Mediterranean and lives between the surface and up to 40 metres deep, creating a lush underwater forest.
Posidonia plants attach themselves to the sea bed by their roots, called rhizomes, either creeping or straight, which grow extremely slowly: about a metre every hundred years!
They provide shelter to a multitude of marine organisms: from algae and small invertebrates which attach to their leaves to small fish threatened by larger species.
Posidonia plants also act as a nursery, housing the larvae of many fish species, but are also a source of food for herbivores such as saupes and urchins.
These aquatic forests also act like the Mediterranean's lungs, producing almost 14 litres of oxygen per square metre per day.
Unfortunately, posidonia plants are threatened by coastal urbanisation, pollution and boat moorings. The plants are closely monitored in the Mediterranean for the crucial role they play in the marine ecosystem.
