Are artificial reefs really effective? Students answer this question with the video "In Search of Reefs."
For over a year, final-year master’s students at the Faculty of Sciences in Montpellier conducted a scientific study on 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 analyzed data from around the world on this topic and interviewed local stakeholders in Agde, a town equipped with artificial reefs. The Mediterranean team is presenting its findings.
Natural reefs are among the most diverse and productive marine ecosystems in the world. They provide essential habitats for many marine species, particularly teleosts (the majority of today’s fish species). However, these ecosystems face significant human-induced pressures (overfishing, pollution, habitat destruction), leading to a loss of biodiversity. To address this, solutions have emerged, such as the creation of Marine Protected Areas (MPAs) or artificial reefs. The study conducted by the students aims to assess the effects of artificial reefs on teleost communities.
AMP and artificial reefs: complementary solutions
MPAs are designated marine areas established to meet conservation objectives and promote the sustainable management of marine activities. According to the 2023 report on the status of MPAs published by MedPAN, only 18% of them have confirmed that they have an active management plan. As a result, complementary management solutions are being considered, such as artificial reefs. Submerged on bare seabed, these structures are designed to replicate certain characteristics of a natural reef, recreating biodiversity hotspots (areas rich in species) and serving ecological functions (refuge, nursery).
The importance of natural reefs extends beyond biodiversity; they also serve economic functions, as 997 million people depend on these ecosystems for food or employment. Engaging coastal users is essential to balancing economic activities with ecological goals, and based on this premise, the students devoted part of their research to this topic.
Underwater photo taken in September 2022 of the main module of Récif’lab, a complex of artificial reefs made of 3D-printed concrete, submerged off Agde. Photo credit: E. Chéré – Agde Coast Marine Protected Area
An analysis of global data
The Mediterranean 2025 Team consists of five Master’s 2 students from different academic tracks, all specializing in B2E (Biodiversity, Ecology, and Evolution). Together, they conducted a meta-analysis, compiling and analyzing data from studies around the world that compare artificial and natural reefs based on several criteria: biomass, density, diversity, and richness of fish communities (see below). They also conducted interviews and street surveys in Agde (Hérault), a port city 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 (in this case, teleosts) present in a given area, such as an artificial reef or a natural reef. “Species richness” refers to the number of different species, while “density” provides an indication of fish abundance, as it corresponds to the number of fish per unit area. The students also considered “diversity,” which takes into account species richness and the relative abundance of each species, allowing them to determine whether a species is dominant in the environment or not.
Photo showing the Mediterranean Team analyzing data using the statistical software RStudio. Credit: Mediterranean Team, 2025.
Artificial reefs are home to communities of teleosts similar to those found in natural reefs!
What were their findings? Their meta-analysis reveals that artificial reefs have higher species richness and fish density than natural reefs. However, diversity and biomass remain similar, indicating that the two types of reefs are equivalent. These observations suggest that synthetic structures effectively fulfill their ecological restoration objectives, with indicators that are comparable to, or even exceed, those observed on natural reefs.
Moreover, these findings are recognized by local stakeholders, clearly demonstrating the socioeconomic benefits of implementing these modules, all of whom support the creation of artificial reefs in their area of operation.
Conducting a scientific study is no easy task, and these budding young biologists decided to document their adventure on video. It’s a unique way to showcase the scientific research process and the scope of 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 past 30 years. Whereas a few years ago any submerged object was considered an artificial reef (such as a car wreck from a junkyard), the practice is now much more strictly regulated. Further studies by students show that the composition of the modules affects their effectiveness; metal and rock have a positive impact on marine communities compared to tires.
Although the Mediterranean Team’s meta-analysis confirms that artificial reefs have a positive effect on teleost communities, they cannot replace natural reefs. Conservation efforts must continue, and artificial modules should be viewed as a complementary tool.
This project was funded by the Faculty of Sciences – Department of Biology and Ecology, as part of the FIRE (Innovative Training through Research) project. The Mediterranean team received support from the Marine Protected Area (MPA) of the Agathois coast as well as from Seaboost, and was supervised by Johann Mourier (lecturer and researcher at the University of Montpellier and biologist at the MARBEC Unit).
Article written by the Mediterranean Team, 2025 – Célia Bourhim, Théo Detambel, Emma Layadi, Anthony Marchand, Nafi Terrasse