Role of the colonization of marine infrastructures on the production of coastal ecosystems in the English Channel

The France – English Channel – England area is subject to increasing human activities, particularly with the development of renewable marine energies, leading to the growth of port areas which, combined with aggregate extraction, fishing, aquaculture, tourism, and maritime transport, further increase the already very high level of pressure in the English Channel.

This accumulation of activities exerts an ever-increasing pressure on the Channel’s marine ecosystem and causes modifications to marine habitats that affect biological diversity, the ecological and sanitary quality of marine habitats, which can potentially modify the services rendered to society by the Channel ecosystem by reducing natural resources. Conversely, the installation of new infrastructures, such as wind farms, can offer new marine habitats and modify the biodiversity and functioning of coastal ecosystems. Reef effects can thus increase the species richness and biomass of structures newly implanted at sea.

My study subject is part of a European project (Interreg Va MARINEFF), which proposes to enable new marine infrastructures to provide benefits as artificial habitats on ecosystem functioning and biological diversity. My work focuses on the colonization of marine infrastructures with the aim of characterizing the establishment of communities and major ecological functions, particularly the production function. The goal is to understand functional diversity and its evolution during the colonization process. The functionality of species is evaluated by analyzing life history traits. Thus, we characterize the redundancies and complementarities of functions and their dynamics over time, and we test different indices of functional diversity. The work takes place in the English Channel on different types of infrastructure made of various materials, on artificial reefs submerged for 5 years, and on natural habitats. Monitoring is primarily carried out by diving with laboratory exploitation of the follow-up samples.

We are interested in primary producer communities and the primary production function of the ecosystem. Photosynthesis measurements using different techniques (benthic chamber, PAM, ppCO2​, etc.) will allow for the performance of eco-physiological measurements indicative of adaptations and acclimatizations based on niches, and for the estimation of primary production balances of the system to quantify trophic transfers. Furthermore, we will carry out measurements of biodiversity, abundances, and biomasses of the main trophic groups. Finally, isotopic analyses will make it possible to specify the trophic level of organisms, from primary producers to top predators.

This study will enable the acquisition of new knowledge on the functioning of hard substrate habitats and, in particular, explore the “biodiversity / productivity” relationship during colonization processes; it will also allow for the implementation of innovative approaches to characterize the functioning of this type of habitat in the context of the development of numerous marine infrastructures present in the English Channel and in Europe. Finally, it will lead to the establishment of protocols and indicators requested by the project partners involved in the construction and management of these structures, in order to assess the negative or positive impacts of such developments at sea.