Saint Martin moves toward floating barrier system to reduce sargassum coast build-up

MARIGOT--The Collectivité de Saint-Martin is moving forward with plans to install floating sea barriers as part of its effort to reduce the accumulation of sargassum along the coastline. Two areas have been identified for the project: Cul de Sac Bay and Embouchure Bay.

The project is supported by an official decision of the Executive Council of the Collectivité de Saint-Martin dated September 29, 2025. In that decision, the Collectivité stated that, based on the “Mission Sargasses 2020” guidance by DEAL Martinique and CEREMA, as well as a feasibility study by DHI and GAÏA, it selected a scenario using floating barriers to protect Cul de Sac Bay and Embouchure Bay.

Following a call for bids, the Collectivité selected the Guadeloupe-based company Antilles Travaux Sous-Marins to carry out the project. The official decision states that the contract covers the supply, installation and maintenance of two sections of anti-sargassum floating barriers, as well as the management of the required regulatory authorizations for one year before transfer to the Collectivité.

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Plans call for four floating barriers in total, with two placed at each site. At Cul de Sac, the barriers would cover a combined length of 700 meters, while another 227 meters would be installed near the mouth of Etang aux Poissons. Installation, including anchoring and deployment of the nets, is expected to take between four and six weeks at Cul de Sac and between two and three weeks at Etang aux Poissons. No start date has been announced.

Once operational, Antilles Travaux Sous-Marins is expected to inspect the system three times during its first year of operation. Ongoing maintenance will be handled by another company under delegation from the Collectivité. In the event of severe weather, including winds above 30 knots and waves higher than two meters, the barriers would have to be removed. Sargassum collected by the barriers would be cleared by the Collectivité’s services.

Because of the environmental sensitivity of the areas involved, the project must follow strict administrative procedures. The barriers would be installed within three kilometers of four natural zones of ecological, faunistic and floristic interest, including areas such as Red Rock and Tintamare. Some sections would also be located near the perimeter of a biotope protection area, as well as within lagoon and marine zones connected to the Marine Reserve and the RAMSAR wetland and marine site.

The project could have effects on natural and marine environments, including the movement of sea turtles and their habitats. To reduce those risks, the company has proposed several safeguards, including carrying out work outside the boundaries of the Cul de Sac Reserve, avoiding ecologically sensitive areas where possible during anchor installation, using swing anchors where feasible and cleaning construction equipment off-site.

The application has been submitted for review to the regional health agency and the prefecture. It will not be subject to a full environmental assessment, although certain parts of the project may still be subject to specific environmental requirements under the Water Act. The project will also require a temporary occupation permit for use of the State’s public maritime domain.

The total cost for installing the system and inspecting it during the first year is estimated at 896,550 euros.

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