Étang de Thau: an experimental project to clean up and restore biodiversity in the Bordelaise area

Un des employés d'Ulysse aidant à retirer une épave de l'eau. Midi Libre – KELMAN MARTI

Ce mardi 13 février, Sète agglopôle Méditerranée a présenté un projet expérimental de dépollution et de restauration écologique sur la zone de la Bordelaise, à Frontignan.

For decades, the seabed of the Thau lagoon has seen disused pleasure boats (BPHU) and macro-waste (tyres, various plastics, etc.)  pile up one after the other. On the site of the Bordelaise pontoon in Frontignan, this Tuesday, some were visible from polluted banks thanks to the sun's rays illuminating very clear water.

From reporting to action

In total, around thirty wrecks are found in this sector of the Natura 2000 network, classified as a Marine Protected Area (MPA). Some for the better, serving and sheltering ecosystems for underwater flora and fauna. Others (almost) for the worse, by simply polluting a diving spot recognized throughout the world for its exceptional biodiversity of seahorses, mother-of-pearl shells or sea slugs.

So much so that Sète agglopôle Méditerranée, the Syndicat Mixte du Bassin de Thau (SMBT), supported by the Biotope design office, launched a project two years ago to restore the funds degraded, after "reports from divers observing these wrecks having nothing to do there", explains Camille Pfleger, project manager Natura 2000.

Continue awareness work

"Biodiversityé of the Thau pond is magnificent. The boats must therefore not be abandoned in this area of ​​Bordeaux", comments François Commeinhes, mayor of Sète and preè resident of SAM. To avoid this problem "which has persisted for a very long time, it is important to continue to raise awareness".&nbsp ;The Blue Brigade takes on this role. "We raise awareness among fishermen, boaters, but also among the youngest in éschools", emphasizes Samir El Mokkedem, head of the organization. "It is always important to remind owners not to abandon their boat, but to entrust them to their owners. APER (the organization responsible for the treatment of waste from boats, Editor's note) which deconstructs them and then enhances them. Çavoids polluting the environment", insists Camille Pfleger.

Experimental project

This Tuesday, on this sweet day, the unifying project, benefiting from the support of the Maritime Prefecture, the Direction
Departmental Territory and Sea (DDTM), the Regional Directorate for the Environment, Planning and Housing Occitanie Region (DREAL), the City of Frontignan, the Waterways of France and local diving clubs, was finally presented by the Agglopôle.

At a cost of nearly 70,000 euros, the National Biodiversity Office (OFB) finances 80% within the framework of Life MarHa. Being one of the first ecological restoration projects, a whole methodology had to be created to decide on the actions to be carried out. Thus, Biotope has designed an analysis grid to "allow the identification of wrecks to be extracted and those to be left in the water" , indicates the design office. The parameters leading to evacuation or not: the size, condition and sinking into the mud of the BPHU, if an ecosystem (seagrass, mother-of-pearl, seahorses, etc.) s& #39;is built and in what proportions, the risks of degrading the environment by removing them…

In total, 15 wrecks, mainly located along the bank and along the pontoon, will leave the pond by next Friday. "We have removed nearly ten since February 9, two this Tuesday morning", list Guy Gradit, from Ulysse maritime services, in diving gear, who took care of strapping them before a 76 m crane lifted them and placed them on the land. After draining, these will then be dismantled and treated.

During the fortnight of work, an order from the Maritime Prefect prohibited the docking of boats. The same goes for land access to the Bordelaise site.

A scientific follow-up

But the work of restoring biodiversity is not limited to the evacuation of 15 wrecks. "During the whole year, in association with diving clubs, volunteer divers will bring macro-waste to the surface", announces Michel Garcia, vice-president of SAM and SMBT.

"In addition, they will conduct scientific monitoring over time to describe the evolution of biodiversity around the boats", adds Nicole Boulay, president of the French Federation of Underwater Studies and Sports. For it to work, "we have to live with the environment, not against it", concludes Michel Garcia.

A project soon to be national in scale ?

After the presentation of this project for depollution and restoration of biodiversity, the question already arises: the question of the future of the new methodology implemented in the Bordelaise area. "The Biotope analysis grid is a good way to decide whether or not to remove wrecks. We will follow the development of the project with great attention", declares Camille Pfleger, Natura project manager 2000 and biodiversity at SMBT.

"This experimentation is necessary to decide the future of the wrecks. This question of the future obviously does not only arise in the Bordelaise area, but on all the edges of the pond and even on the coast. quot;, estimates François Commeinhes.

The future of methodology even seems established. despite the logical lack of results at the moment. The help grid & the decision made by the Biotope studies office will be "deployed on Natura 2000 sites on the Atlantic façade in the course of 2024 in order to test its replicability, indicates the Agglo in a press release ;. "This will allow us to begin thinking about the the nationalization of this method."

In parallel with this national ambition, the Agglo has not forgotten the Thau basin: "The r& The success of this pilot project and the results of ecological monitoring on the lagoon after cleaning will make it possible to assess the interest the effect of the continuation of depollution operations on the Bordelaise site and more generally to establish a new strategy ;gie to address the management of BPHU in sensitive sectors such as the Thau lagoon."

I subscribe to read more