What is Posidonia seagrass?

Posidonia oceanica is a seagrass species found growing in the Mediterranean Sea in depths of up to 40 metres (131 feet). It is one of the oldest living beings on earth, living up to 100,000 years.

Known as the ‘lung of the Mediterranean’, Posidonia forms large underwater meadows and is paramount to the underwater ecosystems by providing important sources of oxygen. Posidonia has a very high carbon absorption capacity, being able to soak up 15 times more carbon dioxide every year than a similar sized piece of the Amazon rainforest. It also protects beaches from erosion by decreasing the power of swell by 20%. Additionally, Posidonia houses over 400 plant species and over 1,000 animal species.

Anchoring and Posidonia

The Posidonia meadows are declining in many parts of the Mediterranean due to pollution, coastal development (such as urban and harbour infrastructure) and fishing activities. The overall decline has been measured as approximately 10% over the last 100 years, but a recent analysis indicates a 34% decline in the past 50 years.

However, the main cause of Posidonia demolition is the mooring of yachts. When a deadweight anchor is dropped, the seagrass meadows are heavily damaged. While the Mediterranean Sea attracts many yachts from 20m to 180m (65ft to 590ft) between May and September every year, the over frequentation of yachts in a concentrated marine environment can be particularly harmful to wildlife, like seagrass, if not properly managed.

Posidonia grows only a few centimetres per year, but hundreds of hectares are ravaged by anchoring each year. Once destroyed, Posidonia cannot be restored.

The protection of Posidonia

Anchoring restrictions

The anchoring of yachts along the French Riviera and Corsica is strictly regulated. Local regulations have been implemented since 2016 to restrict yachts from anchoring in certain locations.

There are serious penalties for captains who do not adhere to the anchoring regulations around Posidonia. Captains can face imprisonment, fines of up to €150,000 (dollars equivalent) and bans from navigating in French Mediterranean waters if these laws are broken.

Discover the anchoring laws for superyachts in the South of France.

Mooring buoys

Various mooring buoys have been implemented across the French Riviera in order to minimise the negative effects of anchoring. Captains can find and book the buoys via the DONIA mobile app.

Find out more about the mooring buoys and how you can book them.

Mediterranean Posidonia Network

The Mediterranean Basin is concerned by the impact of anchoring on Posidonia seagrass. The Mediterranean Posidonia Network was created in order to gather different stakeholders (authorities, marine protected areas, socio-professionals, scientists, associations, etc.) from different countries to find collective solutions to enable eco-friendly mooring along the Mediterranean coast.

Find out more about the Mediterranean Posidonia Network.

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The Yachting Pages website has lots of relevant information for captains about Posidonia seagrass. Visit our Posidonia articles section to find out more.