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What role do Posidonia meadows play?

An ecosystem on its own

Posidonia meadows offer support, shelter, spawning grounds and nurseries for many species.  More than 400 different plant species and several thousand animal species live there, impressive figures if we consider that Posidonia meadows cover less than 1% of the Mediterranean seabed!  In addition, most of the plant material produced is stored and degraded in the matte or ends up in other ecosystems, such as the deep sea or beaches, in the form of dead leaves, which is a real carbon sink.

An ecological and economic interest

A small part of this material forms the basis of the diet for several species of herbivores such as certain sea urchins or salema, the main herbivorous fish of the Mediterranean.

Thanks to their entangled rhizomes, Posidonia meadows stabilize the seabed. They also trap sediments enhancing water transparency.

As a result, the economic value of Posidonia meadows per hectare per year has been estimated at 3 times that of coral reefs, 10 times that of a rainforest and 100 times that of a terrestrial meadow.

Indicator of water quality

Posidonia is considered to be an indicator of the overall quality of coastal waters.  Regular monitoring of the evolution of Posidonia meadows in the medium or long term allows us to obtain information on the quality of the waters.  Indeed, the plant regresses rapidly in the presence of pollutants or mechanical stressors.

In summary, Posidonia plays a role in:

  • Natural protection against beach erosion.  Posidonia banquettes lessen wave energy.
  • Posidonia hosts a multitude of small plants and animals growing on its leaves (called epiphytes), becoming the base of the food chain.
  • Unique biodiversity hotspot, providing shelter, spawning grounds (breeding grounds) or nurseries for many species.
  • Stabilizer of the seabed, thanks to the entangled rhizomes.
  • A carbon sink, producing a significant amount of organic material.
  • Oxygen producer, releasing approximately 14 liters of oxygen per day per m².
  • Indicator of pollution and the overall quality of the environment.  Posidonia provides information on water transparency, hydrodynamics, sedimentation rate, pollutants, and the amount of organic material.