Emblematic of the Mediterranean and essential to the marine ecosystem, Posidonia oceanica (Mediterranean tapeweed) is under threat from large recreational craft when they moor. The weight of these vessels’ chains and anchors and the way they drag through tapeweed meadows are responsible for often irreversible damage. The Fondation de la Mer, supported by Almayuda, is participating in a project to transplant and restore Mediterranean tapeweed in a degraded site now transformed into a pilot experimental lab.
‘For over fifteen years, Mediterranean tapeweed has had to cope with a new threat: the repeated anchoring of large recreational craft. There are 1,700 of these vessels, each more than 24 metres long, that drop their anchors up and own the French Mediterranean coastline. The larger they are, the heavier their anchors and the worse their impact on the sea bottom. They leave huge scars on the tapeweed meadows. These large vessels’ anchors sink and then rip up the leaves and tufts. The roots are exposed in the form of blocks. Any damage done will not be reversed over the course of a human lifespan: in a single night, one ship can inflict wounds that will not heal for more than a century. When the anchor is raised, the sea bottom is ploughed up. Currents of water make the most of the channels opened up by the anchors, rushing in and widening the gashes in the tapeweed meadow. The sediment is then stirred up and the water becomes murky. It is our natural heritage that is disappearing before our eyes…’
These words are taken from a video (https://www.youtube.com/watch?v=ui_Z0389jD0) posted on YouTube by marine biologists working with Andromède Océanologie, with the support of a number of institutional partners, among them the Office de l’Environnement de la Corse. The biologists use powerful images in the video to illustrate the problem of yachts mooring in the Mediterranean, the second pleasure-sailing area in the world after the Caribbean.
What functions does Mediterranean tapeweed serve?
Mediterranean tapeweed is not a type of seaweed but an underwater plant found solely in the sea from which it takes its name. The Mediterranean is already under significant attack and the environmental stakes are high in its threatened ecosystem.
Meadows of Mediterranean tapeweed provide a nursery for underwater fauna, which colonises them at every level. Like forests, these meadows are a refuge for a wide biodiversity of plants and animal life.
Mediterranean tapeweed protects the coastline against erosion. Though swimmers might complain because they do not like to feel underwater seagrasses brushing against them, the tapeweed is kept deliberately close to the shore as it prevents sand being carried away by waves, which would lead to beaches gradually disappearing.
It produces oxygen and is one of the most important carbon sinks in the Mediterranean. This role is even more essential in relation to the acidification of seawater caused by CO2, which in the long term can stop seashells from forming and even damage the skeleton of plankton and hence threaten their very existence. If they were to go extinct or become scarce, it would be a disaster for fish and more generally an environmental catastrophe.
Dragging and ploughing
Mediterranean tapeweed is a plant that has roots and flowers. To reproduce, it needs sunlight. Photosynthesis takes place between 0 and 40 metres, a depth that matches the mooring zones of large recreational craft.
The chains and above all the anchors of these vessels crush everything and then, when they are raised, they drag, leaving the sea bottom deeply furrowed. Over time, everything is ripped out and uprooted and nothing will grow. The turbidity that permeates the depths stops photosynthesis and the root system can no longer play its part as a water purifier. Channels are dug where the tapeweed has been torn out and water currents flow in, accelerating the erosion.
Viewed from Corsica, these phenomena clearly affect the entire Mediterranean coast. To remedy the situation, mooring sites need to be regulated, for example by creating ZMELs (Mooring and Light Equipment Zones). However, efforts must also be made to restore and replant Mediterranean tapeweed in places where it has been eradicated.
This is precisely the mission of the Mediterranean Tapeweed Transplant project, which is supported by the Fondation de la Mer, with the Région Sud, Agence de l’Eau and the Office Français de la Biodiversité as its principal partners.
Transplanting and restoration
The Fondation de la Mer was set up in 2015 ‘at the service of all those working towards an ocean that is sustainably protected and exploited with care and wisdom.’
The foundation aids local actors in implementing their own programmes to protect marine biodiversity, to combat pollution of the sea, to support research, to encourage innovation, to educate and to raise the public’s awareness, in particular among young people.
The particular project that Almayuda is lending its support to consists of restoring and repopulating an experimentation site with Mediterranean tapeweed. This site will be a ravaged area that is now a regulated, ‘organised’ mooring of the ZMEL type.
In this area criss-crossed with scars caused by anchors and covered with a dead mat of once living meadow, scientists and experts from the laboratories of the Institut Méditerranéen d’Océanologie (MIO) of Aix-Marseille Université and Equipe Ecosystèmes Littoraux (EqEL) of the Université de Corse will be replanting Mediterranean tapeweed.
They will also be attempting to get it to root and grow on hard surfaces such as mooring facilities and buoys. In short, this is an environmental engineering mission involving both natural and manmade surfaces.
The Almayuda Foundation is pleased to participate in this programme expected to last three years that will result in innovations in protecting and restoring one of the marine ecosystems that are a priority for Corsica and the entire Mediterranean. Also in Corsica, the Almayuda is at the same time supporting the U Riparu research project related to preventing plastic waste at sea.
Photos : DR
Useful links: https://www.fondationdelamer.org/
https://www.youtube.com/watch?v=ui_Z0389jD0