L’Office français de la biodiversité manages le Parc naturel marin du Bassin d’Arcachon.
Created on June 5, 2014, the Arcachon Bay Marine Nature Park covers an area of 435 km² of marine space, between a semi-enclosed lagoon and the ocean coast. It includes the inner-basin area and the Atlantic waters up to 3 nautical miles offshore (approximately 5.5 km).
The Marine Nature Park borders 10 municipalities and encompasses 144 km of coastline. Its boundaries border those of Lège-Cap Ferret to the north and La Teste-de-Buch to the south.
Marine Park Map ©️ L’Office français de la biodiversité.
Our shared vision
The Seagrass Consortium works to support the vision for seagrass restoration as set out by the management board of Le Parc naturel marin du Bassin d’Arcachon in the governing document Le Plan de gestion du Parc naturel marin du Bassin d’Arcachon.
Specifically, we seek to support the marine park with the restoration of both Zostera marina and Zostera noltii meadows to their target of ‘a similar surface area and density as observed in the early 2000s’. This is directly in line with the vision set out by the marine park on Page 40 of Le Plan de gestion).
Historical context
| Year | Zostera marina | Zostera noltii | Source |
| 1989 | 381ha | 6846ha | Auby (1991) |
| 2008 | 104ha | 4569ha | Plus et al. (2010) |
| 2012 | 4259ha | Lafon et al. (2013) | |
| 2016 | 56.2ha | Trut et al. (2018) | |
| 2019 | 3856ha | Rigouin et al. (2019) | |
| 2024 | 80.1ha | Rigouin et al. (2024) | |
| 2026 | TBC | TBC | |
| Compared to our ‘baseline’ ; the largest known seagrass meadow surface area. | -79% | –44% |
Since the creation of Le Parc naturel marin du Bassin d’Arcachon in 2014, a great deal of work has been done both by the marine park at its partners to reduce the environmental pressures on the marine ecosystems. Recent WFD mapping (Zostera marina in 2024, Zostera noltii in 2025) show that these ongoing restoration efforts are working, with recent mapping by Ifremer Station d’Arcachon showing a positive trajectory for both Zostera noltii and Zostera marina (~25ha restored passively between 2016 and 2024).
Restoration in numbers – the data.
Key Performance Indicators and milestones we’ve achieved since 2023.
22,500
Zostera noltii seeds planted
L’Office français de la biodiversité initiated seed-based Zostera noltii restoration within le Parc naturel marin du Bassin d’Arcachon in 2022 following their first Zostera noltii seed collection in 2021.
Seed-based Zostera noltii restoration has since been undertaken every year, utilising the seeds that collected by the annual seed collections (‘Chantier participatif‘s) which are organised by the L’Office français de la biodiversité every summer on the Île aux Oiseaux. Le Parc naturel marin du Bassin d’Arcachon had already planted
2,000
Zostera marina seeds planted
In 2024 l’Office français de la biodiversité initiated seed-based Zostera marina restoration within le Parc naturel marin du Bassin d’Arcachon following their first Zostera marina seed collection.
In 2025, following the 2024 restoration pilot, Zostera marina has been recorded growing for the first time in both the north and the east of the Bassin d’Arcachon since the loss of the meadows in the early 2000s.
6,613
Zostera noltii sods transplanted
Sod-based Zostera noltii restoration is achieved by utilising 10cm ⌀ cores for moving plants between donor meadows and restoration sites.
Sods of 10cm ⌀, and around 10-12cm depth are collected from healthy donor meadows (where there is lots of seagrass) and are transplanted onto bare mid flats (where there was previously seagrass, but where it is no longer present).
The exact design of the transplant ‘restoration plots/stations’ varies depending on the characteristics of the site.
2023 – 1026
2024 – 2286
2025 – 3301
30
Zostera marina sods planted
In 2024 l’Office français de la biodiversité also trialed small-scale sod-based Zostera marina restoration.
This initial pilot revealed mixed results, and so priority is now on exploring the the potential for growing Zostera marina seagrass in confined conditions (a seagrass nursery) which could then be used for restoration outplanting trials.
2nd European Seagrass Restoration Workshop
Long-term vision
Key Performance Indicators and milestones we’ve achieved since 2023.
2
Large-scale restoration sites
Within le Parc naturel marin du Bassin d’Arcachon two ‘large-scale’ (1ha+ restoration sites) have been identified so far. These are locations where either seed-based or sod based restoration is proving successful.
To this end we are now actively transplanting and seeding seagrass at two restoration sites “Salines” and “Gaillard”.
200+
Test stations
Since 2021 le Parc naturel marin du Bassin d’Arcachon have transplanted Zostera noltii at over 200 test stations across the Bassin d’Arcachon. This pilot work is enabling us to narrow down suitable restoration sites for active restoration.
Discover the Vibrant Restoration Site Gallery
This section features a carefully selected array of images capturing the ‘day-to-day’ actions and the progress of our seagrass restoration efforts.
Local Partners and Initiatives
The seagrass restoration in le Parc naturel marin du Bassin d’Arcachon relies on a close collaboration with, and the expertise of, a number of local partners and initiatives.
Ifremer station d’Arcachon
Le laboratoire côtier d’Arcachon is responsible for the ongoing monitoring and data collection missions on the quality of the coastal marine environment. The station d’Arcachon team provides both expertise and decision-making support to local and regional institutional partners; particularly in the areas of seagrass ecology, hydrodynamics, water quality and aerial remote sensing.
Scientific collaborations
What if we could shield young seagrass plants germinating from seed by transplanting older plants around them? This European collaboration is testing whether an outer barrier (a U shaped ‘hug’) of seagrass helps seedlings of either the same or different species grow better inside.
Similar experiments are being replicated at several sites across Europe including in the Étang de Berre, Bay of Santander, in Mallorca and in the UK.
Science, collaboration, and restoration, all wrapped into one hug.
Seagrass Nursery
In collaboration with the Lycée de la mer Gujan le Parc naturel marin du Bassin d’Arcachon is exploring the viability of a seagrass nursery. This will be an opportunity to experiment with seagrass and potentially produce seagrass seeds and propagules in semi-controlled conditions. The long term aim is to maximise germination success rates and seedling survival to support the seagrass restoration programme.
Oyster Malines
It is known that the presence of seagrass helps oysters by improving shell growth. However there is also a growing body of evidence to show that seagrasses filter pathogens in marine waters.
In situ research is now requested to quantitatively establish whether the seagrasses of the Bassin d’Arcachon (both Zostera marina and Zostera noltii), and particularly those seagrass meadows present in the Oyster Malines, are filtering pathogens from the water and reducing the pathogen load on the commercially important Pacific Oyster (Magallana gigas).
Genetics and Morphometrics
In 2025 a PhD candidate at the Rijksuniversiteit Groningen has been running a climate change mesocosm experiment utilising seagrass from the Bassin d’Arcachon. She has collected data on relative germination success, the above and below ground biomass of the succesfully germinated plants and their associated genetics.
This data is being collected to help inform decisions around climate proofing restoration into the future.
Chantiers participatifs
Since 2021, le Parc naturel marin du Bassin d’Arcachon has been calling on citizens every summer to collect a large number of Zostera noltii seeds. These seeds are then sown in the autumn and spring to attempt to recolonise areas of the Bassin d’Arcachon from where they have disappeared.
Espace pédagogique
Le Parc naturel marin du Bassin d’Arcachon celebrated its 10th anniversary in 2024, and with a view to enhancing public awareness of both the productivity, but also the fragility of the Bassin d’Arcachons marine ecosystems, the park opened a new educational space in Gujan-Mestras, on the port of Larros.
Restoration Overview
Discover the detailed restoration phases, providing insight into site-specific actions and progress monitoring led by the Seagrass Consortium.
Phase One: Site Assessment
Initial evaluation of site conditions and ecological factors critical for planning effective seagrass restoration efforts.
Phase Two: Restoration Implementation
Execution of restoration activities including planting, habitat enhancement, and continuous site management.
Phase Three: Monitoring & Reporting
Ongoing monitoring to assess seagrass recovery, ensuring the restoration goals are met and informing future improvements.