Seagrass and Macroalgae Imitations improve Marine Habitat Functions on the French Mediterranean coast

Seagrass meadows and macroalgal forests are known to create rich ecosystems, that provide numerous ecosystem services, for example food provisioning, carbon storage, and erosion control. The Mediterranean coast in France has undergone significant artificialization due to urbanization, tourism, and industrial activities. Coastal development has led to the construction of ports, marinas, coastal defenses, and urban infrastructure, which have impacted natural habitats, leading to biodiversity loss and changes in coastal dynamics. Efforts are being made to balance development with conservation through coastal management plans and regulations aimed at protecting and restoring natural habitats.

In this project new habitat was created at the Cape of Agde, on the Mediterranean French coast by deploying structures that resemble seagrass meadows and kelp forests, with the aim to prevent local erosion and enhance local fish abundance and diversity. This demonstration was settled in the frame of an experimental project aiming at eco-designing underwater cables and supporting sediment stability in their vicinity for risk mitigation concerns. The structures were deployed on sand at shallow depths and monitored for sediment movements, water currents, and biodiversity monthly over a 7-month duration (March-October 2024).

Results indicate a strong increase in fish abundance during the day, as well as an increase in cephalopods during the night. The structures both served as a hiding habitat and feeding ground, with slightly better results for the macroalgae imitation. Both structures showed colonization of different organisms, with Fucus settling on the seagrass meadow imitating structure and mussels growing on the macroalgae imitating structure.

Overall, the project can be considered as a successful eco-design project, since the presence of the structures have had positive effects on the biodiversity and fish abundance and have proven to provide a wide range of habitat functions. That kind of approach may be settled as an addition for marine or offshore project in order to tackle biodiversity impacts and support or restore local nursery and habitat ecological functions.

 

Keywords: Ecological Restoration, Marine Environment, Ecological Functionalities, Seagrass, Eco-design, Impact Mitigation, Nursery, Habitat