Are artificial reefs really effective? Students answer with the video "In search of reefs".
For over a year, students in their final year of a Master's degree at Montpellier's Faculty of Science have been carrying out a scientific study of artificial reefs, structures submerged in the sea to recreate natural habitats. The students asked themselves: are these modules effective? What impact do they have on fishermen, divers and other users? The group of five examined data on the subject from around the world, and interviewed local stakeholders in Agde, a town with artificial reefs. The Mediterranean team reports its findings.
Natural reefs are among the world's most diverse and productive marine ecosystems. They provide essential habitats for numerous marine species, notably teleosts (the majority of today's fish species). However, these ecosystems are under heavy anthropogenic pressure (overfishing, pollution, habitat destruction), leading to a loss of biodiversity. To remedy this situation, solutions have been found, such as the creation of Marine Protected Areas (MPAs) or artificial reefs. The students' study aims to assess the effects of artificial reefs on teleost communities.
MPAs and artificial reefs: complementary solutions
MPAs are delimited areas at sea that meet protection objectives and promote the sustainable management of maritime activities. According to the report on the status of MPAs published in 2023 by MedPAN, only 18% of them have confirmed that they have an active management plan. As a result, complementary development solutions are being considered, such as artificial reefs. Submerged on bare soil, these structures are set up to reproduce certain characteristics of a natural reef, recreating biodiversity hotspots (species-rich areas) and fulfilling ecological functions (refuge, nursery).
The importance of natural reefs is not only linked to biological diversity, but also to economic functions, since 997 million people depend on these ecosystems for food or work. The integration of coastal users is essential if economic activities are to be reconciled with ecological objectives. With this in mind, the students devoted part of their research to this subject.
Underwater shot in September 2022 of the main module of the Recif'lab, a complex of artificial reefs printed in 3D concrete, submerged in Agde. Credits: E. Chéré - AMP côte agathoise
An analysis of global data
The Mediterranean 2025 Team is made up of 5 Master 2 students from different courses, all from the B2E (Biodiversity, Ecology and Evolution) specialization. Together, they have carried out a meta-analysis, compiling and analyzing elements from studies around the world that compare artificial and natural reefs on several criteria: biomass, density, diversity and richness of fish communities (see below). They also conducted interviews and micro-trotters in Agde (Hérault), a port town that has been participating in an artificial reef immersion program for several years now.
Explanations of the different metrics: "Biomass" represents the total mass of the individuals studied (here teleosts) present in a given area, in this case an artificial reef or a natural reef. Specific richness" indicates the number of different species, while "density" gives an idea of fish abundance, since it corresponds to the number of fish per unit area. The students also took into account "diversity", which takes into account the specific richness and relative abundance of each species, making it possible to highlight whether a species is dominant in the environment or not.
Photo of data analysis by Équipe Méditerranée using RStudio statistical software. Credits: Équipe Méditerranée, 2025.
Artificial reefs are home to teleost communities similar to those found on natural reefs!
Their findings? Their meta-analysis reveals that artificial reefs have a higher species richness and fish density than natural reefs. However, diversity and biomass remain similar, indicating that the two types of reef are equivalent. These observations mean that synthetic installations are fulfilling their ecological restoration objectives, with indicators close to, or even higher than, those observed on natural reefs.
What's more, these conclusions are perceived by local stakeholders, demonstrating a socio-economic link in the immersion of these modules, all of whom are in favor of setting up artificial reefs in their area of activity.
Conducting a scientific study is no easy task, and the budding young biologists have decided to document their adventure on video. An original way of presenting the scientific research process, and the scope of the work involved in such a project. The video is available at the end of this article.
A complementary tool, not a substitute
The concept of artificial reefs has evolved over the last 30 years. While a few years ago, any submerged object was considered as such (car wrecks from garbage dumps, for example), the practice is now much more regulated. Complementary studies by the students show that the composition of the modules has an impact on their effectiveness, with metal and rock having a more positive effect on communities than tires.
Although the Mediterranean Team's meta-analysis confirms a positive effect of artificial reefs on teleost communities, they are no substitute for natural reefs. Conservation efforts must continue, with artificial modules seen as a complementary tool.
This project was funded by the Faculty of Science - Department of Biology and Ecology, as part of the FIRE (Formation Innovante par la Recherche) project. The Mediterranean team benefited from the support of the Aire Marine Protégée (AMP) de la côte agathoise and Seaboost, and was supervised by Johann Mourier (teacher-researcher at the University of Montpellier and biologist at the MARBEC Unit).
Article written by l'Équipe Méditerranée, 2025 - BOURHIM Célia, DETAMBEL Théo, LAYADI Emma, MARCHAND Anthony, TERRASSE Nafi