Artificial Reefs: A Solution For Biodiversity In The Mediterranean?

Divers in the sea setting up an artificial reef in Algeria
15-38 Méditerranée
Marseille, France
Artificial Reefs: A Solution For Biodiversity In The Mediterranean?

Off the Prado beach in Marseille, a new count took place in September 2022. For the professional divers brought together by the Marseille city council on a voluntary basis after the summer heat wave, the challenge was to measure the effects of the increase in temperature under the sea on marine species, especially in the protected area around the artificial reefs installed 14 years ago. Hervé Menchon, elected representative for the sea and biodiversity in the city of Marseille, is waiting for the results of the count with some concern. 

This particular and symbolic area has seen its biomass increase by 264% after 10 years of implementation according to the scientists in charge of monitoring the project. On the sandy seabed of the Prado, which had become almost deserted, life has returned over the years since the implementation of what is now the largest artificial reef project in Europe and the Mediterranean. In 2008, the RECIFS PRADO program (Ecological, Concerted and Innovative Rehabilitation of Sandy Bottoms by the Installation of Diversified and Optimized Artificial Reefs) allows the installation of more than 400 concrete structures imitating coral habitats at a depth of 25 m, between the harbor of Endoume and the Frioul islands. Concrete in the form of cubes, chains or metal structures filled with blocks are arranged in six "villages" linked together over a length of about 300 meters.


The alert was given this summer by diving associations and other actors of the sector: in some areas of the harbor of Marseille, while temperatures of 27 degrees were measured underwater, species such as Gorgonians are threatened with extinction, and, conversely, some invasive exotic species are making an appearance. 


Studies conducted between 2019 and 2021, after ten years of immersion, show that the number of fish present increased very rapidly the first year and then remained stable, with significant variations according to the season: "A peak occurs in October year after year, it is a time of diversity for the biomass," says Laurence Le Diréach, a member of the Scientific Interest Group for the Marine Environment, in charge of monitoring the reefs. Some fish have grown larger and bigger, and some predatory species at the top of the food chain have been able to replace other species that feed on plankton.

Installed to boost fishing activity in the area, the biomass of species particularly prized by fishermen has increased by a factor of 2.6 since the beginning of the monitoring. Conger (x7.6), sharp-snouted seabream (x22.9), mostelle (x18.1) and capon (x12.6) are the species with the largest increases in biomass since 2009.

infographics showing the evolution of biodiversity in the prac artificial reef
Evolution of the biomass of species in the artificial reefs of the Prado, in Marseille, in 2009 (2), 2013 (3) and 2020 (4). Each fish represents its category in the food chain. The boxes represent the evolution of the biomass. It can be seen that the biomass of carnivorous fish has increased. Source: Report of the Scientific Interest Group for the Marine Environment, 2022 / Graphic design credit: Louise Dib via Chimbo.




Improvement of biodiversity


These positive results are not limited to the Marseille experience. On the other side of the Mediterranean, divers from Annaba, in eastern Algeria, immersed four reefs of 3 or 4m3 in 2016. The initiative is an experiment of divers from an association of the city, Hippone Sub, associated with an Algerian network of protection of marine biodiversity, called Probiom. Here too, the first effects are rapid: "Within six months, algae had colonized the metal frame, squid and shellfish eggs were attached to the frame, and small damselfish could be seen. The first link of the trophic chain was there," reports Farid Derbal, teacher and researcher of the Department of Marine Sciences of the University of Annaba, but also diver and vice-president of the association Probiom. Five years later, and contrary to Marseille, the associations of Annaba were not able to make a scientific study on the impact of these artificial reefs, for lack of means. But the various dives carried out by Professor Derbal allow him to note an evolution.

"We have counted more than sixty different species of fish present in the reefs. In 2021, we were able to observe a school of silts, predatory fish: this means that a reef can attract fish. We also noticed that the reef was occupied by scorpion fish, wrasses (a family of carnivorous fish) and damselfish, and that octopus and groupers were sometimes observed. If we cannot measure the evolution of the biomass, it is clear that in terms of species diversity, it is an improvement."


drawing and inforgraphics of a triangle shaped artificial reef in the sea
Artificial reefs have three main uses. By increasing the quantity and diversity of species present, they can increase the resources for fishing and generate interest in recreational diving, thus boosting this tourism sector. Finally, their structure can also act as a protection, by delimiting a fishing area or a protected area and by preventing the vessels from advancing, or also by deflecting the currents. Source: F. Derbal, University of Annaba / Graphic design credit: Louise Dib via Chimbo.


At the beginning of 2021, the divers of Hippone Sub and the Probiom network will immerse an extension of the artificial reefs. This time, two large metal structures of 33 and 66m3 in the shape of pyramids are installed. They include metal chains and a series of earthenware jars. "From the 2016 experience, we know that metal is the most efficient material. The jars were given to us by a craftsman and we knew that Tunisian fishermen use it to develop the presence of octopus," explains Emir Berkane, doctor, environmental activist and president of the Probiom Foundation (a network of Algerian associations for the defense of the environment). The initiative is seen as a first response to a loss of biodiversity: "At the local level, some species are disappearing, and others are losing density," says Samir Grimes, lecturer at the Algiers National Marine Science and Coastal Management School (ENSSMAL) and national coordinator of the Algerian database on biodiversity. The researcher underlines the erosion of biodiversity at the scale of the Mediterranean basin. 

Divers prepare the immersion of the pyramid structure off Annaba, Algeria
Divers prepare the immersion of the pyramid structure off Annaba, Algeria. 2021 / Credit: Probiom.


One in five species is threatened


The Mediterranean harbors more than 17,000 marine species, or 18% of the world's known marine species, while its surface area represents only 0.83% of the planet's waters, according to UN organizations. Among these species, more than a third are endemic species, that is to say that they exist nowhere else on the planet. However, this ecosystem is in danger. 32% of threatened marine habitats in Europe are in the Mediterranean Sea, with 21% considered vulnerable and 11% endangered, according to the Mediterranean Experts Network on Climate and Environmental Change (MedECC). This threat includes several valuable and unique habitats (seagrass beds and coralligenous), home to a great biodiversity. One species out of five would be on the way to extinction, according to a study conducted by the Tour du Valat Institute and published in 2021.

"Unsustainable fishing practices, non-native species, warming, acidification and water pollution threaten marine food production and may affect species distribution and lead to local extinction of more than 20% of exploited marine fish and invertebrates by 2050," warns the Mediterranean Experts on Climate and Environmental Change (MedECC) in their first report for the 2020 region.


It is indeed human activity that is responsible for the situation. An anthropogenic responsibility highlighted in the Sixth Report of the Intergovernmental Panel on Climate Change (IPCC). In a report on maritime transport and climate change, the United Nations recalls that "the Mediterranean is one of the world's busiest seas, carrying 20% of world maritime trade, 10% of container transit and more than 200 million passengers.

Marseille is the leading port in France and the second largest in the Mediterranean in terms of cargo tonnage. The 57 kilometers of the harbor are particularly subjected to the pressure of human activity; fishing, wastewater discharge, tourist frequentation, noise pollution, the coastal ecosystem suffers and disappears little by little. Until the 2000s, some studies estimate that the fish biomass has decreased by 80 to 90%. To reverse the trend, the restoration of degraded ecosystems is one of the avenues presented in a report by Ifremer (French Research Institute for Exploitation of the Sea). The reef project off the Prado is therefore essential to restore the ecosystem. In this area, diving, fishing and swimming are prohibited by an order of the prefecture until 2024, for the time being.


But this solution seems difficult to implement in the whole region because maritime traffic is transit traffic: "The Mediterranean allows primarily the exchange of manufactured goods between Europe and Asia and the supply of energy products to Europe from the Gulf countries," according to a report by the Urban Planning Agency of the Marseille agglomeration. 


Industrial port of Algiers
Merchant ships dock at the port of Algiers / Credit: Marie-Eve Brouet.


A few nautical miles away, the French National Institute of Marine Sciences (Ifremer), a French public institution for research and innovation to protect and restore the oceans, is experimenting with solutions on 230m3 of submerged reefs in the Toulon harbor to restore biodiversity in areas that are still active. "From a pragmatic point of view, it is difficult to imagine being able to stop human activity wherever it has had an impact on the seabed," says Marc Bouchoucha, who monitors these projects for Ifremer. Today, 44% of the world's population lives less than 150 kilometers from the coast, the scientist reminds us. The artificialization of the coastline, which modifies and destroys the natural habitat, is one of the main causes of biodiversity loss.


In France, the first artificial reefs were implanted in the 1960s, sometimes by choosing tires or old cars that were eventually removed because of the pollution they caused. In Marseille, after feasibility studies, the city launched the RECIFS Prado project in 2000, in consultation with public, associative and scientific actors. "In Algeria, the initiative came from the associative movement, explains Professor Farid Derbal. Small experimental reefs have been set up based on the experience of diving clubs. The associations then reflect on the choice of suitable sites that would be a problem "neither for navigation, nor for fishermen, nor for the army". 

underwater photo of a pyramidal shaped artificial reef
The divers of the Hippone Sub association weld the elements of the artificial reefs under water. Annaba, 2021/ Credit: Probiom.


One of the conditions for the success of a reef is to vary the shapes, the sizes, the light "in order to reintroduce a multitude of natural functions", explains Thomas Paquereau, marine biologist and professional diver. "Structural complexity is the key to covering a wide range of species and individuals within a species," he details. Attention must also be paid to the materials used so as not to have a negative impact on the aquatic environment with elements that are released from the materials due to immersion: unpurified metro trains, concrete used and its adjuvants and chemical products, paints, etc. The company for which Thomas Paquereau works in Marseille has chosen to use simple metal structures without concrete. "Thanks to an electrolytic process (linked to a low voltage power supply), the metal immersed in water aggregates the surrounding sediments and mineral salts. The material formed has the objective of fighting against erosion and preserves marine biodiversity by recreating the habitat function," he says.


"In the end, the main challenge of a good reef is to create biomass in order to offset the carbon cost of the installation in a concerted environment; coastal development, fishing and tourist activities, etc.," says Thomas Paquereau. "Manufacturers and politicians should also think of adaptable reefs, adjustable in size according to the targeted species."

Artificial reefs in the sea
Artificial reefs in the port of La Seyne-sur-Mer, Ifremer. 2020 / Credit: Dugornay Olivier.


Ecological corridor 


Despite their usefulness, reefs do not work miracles everywhere. In the Calanque de Cortiou in Marseille, reefs were submerged in 2017. "Today, they allow the creation of shelters and feeding areas for certain species, but they have not created a sufficient ecological corridor," explains Hervé Menchon, the elected representative for the sea of the city of Marseille. The seabed of this cove, which has been subjected to industrial and wastewater discharges for many years, is severely damaged and the reversibility of the damage is uncertain.

"From an ecological point of view, the question of leaving the reefs in immersion arises, because the fish that feed on these reefs are in contact with the polluted funds and then join the food chain or will be fished and then consumed, "says the elected official. Today, the situation seems unsatisfactory and the reefs have not solved the more general problem related to the quality of fresh water that flows into the cove.


"The reefs have a positive psychological impact," said Samir Grimes, a lecturer at the National School of Marine Sciences and Coastal Management in Algiers (ENSSMAL). They create dynamics, and they are a solution on a micro scale."

"However, installing reefs should not send the message: We can still pollute. If there is marine pollution, it affects the populations of artificial reefs as well. The real solution to combat the erosion of marine biodiversity is to regulate fishing, fight against all forms of pollution and adapt to global warming," he believes.


In Marseilles, the cost of the reefs, in addition to the cost of their immersion (six million euros in the case of Prado, financed at 40% by the European Union, 30% by the RMC Water Agency, 10% by the Region and 20% by the City of Marseilles), is significant. The maintenance and monitoring of the program represents several million euros, including the establishment of a patrol dedicated to securing the area, or the replacement of some key materials of the structure. The elected representative for the sea decided to launch a study to determine whether projects like the Prado reefs would be renewed. Without denying the importance of this cost, Marc Bouchoucha, from Ifremer, reminds us that the installation of such facilities also represents economic benefits: maintenance of fishing activity, sales of diving and fishing equipment. 

Close up photo underwater of a Cratena peregrina
Hervia caperine (Cratena peregrina) in an artificial reef, Ifremer. 2020 / Credit: Dugornay Olivier


In Annaba, Emir Berkane highlights a "certain administrative tenacity" to explain the success of the immersions, but also the financial means. "For this project, we had financial support from the United Nations Development Program (UNDP) which allowed us to build the pyramids and a special barge to transport the modules. I am sure that with funding, the artificial reef projects of Skikda, Algiers, Oran could have succeeded. However, the divers and welders worked voluntarily, the association Hippone Sub lent its boats and financed the fuel.

"If we put a price tag on diving and paying scientists for their work, the budgets would explode. These reefs should be government projects." says Emir Berkane. “Funding does not make projects successful," says Grimes.  This financing must be sustainable and involve all the players.

The Algerian divers have well understood the necessity of a large mobilization. The Probiom network, after having noted that the absence of legislation on artificial reefs was a hindrance, contacted the authorities and the press, to underline the need for a law. Their lobbying worked: a decree was adopted in 2017 and the law gave wilayas (the equivalent of prefectures) the power to issue permits for the immersion of artificial reefs. However, this does not solve all the problems and brings new ones.

"Almost no one has been able to go through with the process. The wilaya committee has 12 members representing the institutions. It's more complicated because for most of these people, artificial reefs are science fiction," says Emir Berkane. 

While they are immersing their pyramids, divided into 1m3 modules bolted together underwater, the Probiom network and the divers of Hippone Sub have another project: to immerse a hundred abandoned train cars. The project, entitled "The Wagons of the Sea", requires significant funding to ensure logistics, scientific monitoring over five years and the depollution of the wagons before their immersion. The national hydrocarbon company Sonatrach was willing to support them, while it wanted to develop offshore exploitation. But since a change of government in Algiers at the end of 2019 and the freezing of offshore projects, the associations have no news.

A diving association has built a special barge and a freight elevator to be able to submerge its artificial reefs
The Hippone diving association has built a special barge and a freight elevator to be able to submerge its artificial reefs. Annaba, 2021 / Credit: Probiom.


Essential political collaboration


If convincing the Algerian authorities to authorize the immersion of reefs seems to be an obstacle course, collaboration is essential to achieve political mobilization. The success of an artificial reef also depends on other environmental protection actions carried out before or in parallel.


In France, the installation of wastewater treatment plants on the coast, one of the first ecological restoration projects, has demonstrated its effects on biodiversity thanks to concerted actions: the restoration is total in certain sectors, such as Cap Sicié, a few kilometers from Toulon. Yesterday, devastated by wastewater discharges, the underwater bottoms of the area saw the return of anemones, starfish or sea urchins, witnesses of a good water balance. "This success is linked to the implementation of a real financing engineering and governance for its management with the water agencies," explains Marc Bouchoucha. "This is more complicated in terms of managing underwater biodiversity because the destruction is invisible and the areas are larger," he adds.


For the researcher, the most effective way to consider the restoration of a natural environment is first to remove the pressures, then to reintroduce ingenious species that will recreate the habitat, such as the flat oyster or the Posidonia meadow. According to him, reefs are only a third step. The greatest successes of restoration have taken place in contexts of passive restoration, as is the case for some Mediterranean lagoons. "We stop the various pressures and let the system return to its natural functions. In port areas, this is called active restoration by adding elements to restart the system. But it would be utopian to imagine not having a port anymore," insists Marc Bouchoucha.


"Reefs have an interest when the ecosystem is degraded and we try to replace it," summarizes Farid Derbal, professor at the University of Annaba. But reefs can not do everything, stress the Algerian associations. "We need marine protected areas. But we can't get them done. It takes money and the involvement of all the players," explains Emir Berkane. In Marseille, Laurence Le Diréach insists on the role of reefs "as a complementary tool" for biodiversity management. Marine protected areas, artificial reefs, the range of actions is wide and each tool has its role to play.

Image of a Sabella a type of worms living in a tube buried vertically in the sand, from which emerges a plume of feathery gills. It is observed here in the artificial reefs of the port of La Seyne-sur-Mer
A sabella in the artificial reefs of the port of La Seyne-sur-Mer / Credit: Ifremer


Marine Protected Areas and insufficient regulation 


"While marine protected areas cannot stop climate change and its consequences, such as ocean acidification, they are an important tool for improving the resilience and adaptive capacity of ecosystems," the Mediterranean Experts on Climate and Environmental Change (MedECC) also state. Marine protected areas do exist in the Mediterranean: in 2020, 8.33% of the Mediterranean Sea was under protected status, according to the MedPan association, responsible for promoting the creation, perpetuation and operation of a Mediterranean network of Marine Protected Areas. 


However, according to a study by the Centre for Insular Research and Environmental Observatories (a team led by the CNRS), 95% of these areas are "lacking sufficient regulations" to "reduce human impacts on biodiversity". According to these researchers, only 0.23% of the basin is actually protected. "Due to a lack of human and financial resources, many MPAs created in the Mediterranean are not effective and do not meet their objective of preserving marine environments," says the MedPan association, which is launching a financial support program worth $40 million for 20 official marine protected areas and those being created. The objective is to protect 220,000 hectares across Albania, Algeria, Lebanon, Morocco, Montenegro and Tunisia.


In Algeria, there are two official marine protected areas, off Oran, in the west of the country: The Habibas Islands and the Plane Island. Procedures are underway to extend the status of National Park to the marine part of the national parks of El Kala (east of the country) and Gouraya (near Bejaia, in the center of the country). "Algeria had already identified a dozen sites to be protected in 1997, recalls Samir Grimes. What is missing is the establishment of effective management structures that guarantee funding. It is a political issue. Management difficulties in European MPAs are also highlighted in a report by the European Union's Court of Auditors in 2020: according to the institution, the MPA network is "failing" to provide protection. 


Towards more efficient cooperation 

Increasing the impact of these policies seems to require international cooperation. "The countries of the northern shore have experience in managing marine protected areas. This experience can save us time. Any action on the southern shore will have an impact on the northern shore, in the same way that pollution in Spain has an impact on the French coast, or that protected areas in Corsica have a positive impact in Italy. We need to think in terms of common biomass," says Emir Berkane, President of Probiom.


"Exchanges of experience exist in the Mediterranean, but not in a concerted manner, rather by opportunity," says Hervé Menchon, the elected representative of the City of Marseille. On the Algerian side, the associations have asked the French Development Agency for support in creating a twinning with Prado. At the UN Oceans Conference in June 2022, participating countries commit to "improve cooperation" and find "innovative financing solutions.

"We need to rethink international cooperation on the issue of marine biodiversity preservation," warns Samir Grimes. "There is a lot of funding, but the cooperation is not done strategically enough: organizations work in a project logic, which involves workshops and deliverables, but we do not ensure the sustainability of these deliverables," he laments.

In Lisbon, in the face of the discussion on the constraints to be put in place from an international point of view, several countries put forward the fact that their responsibility in the degradation of the oceans is very limited. the responsibility is shared," says Grimes. The IPCC Special Report on Seas and Oceans proves the link between climate biodegradation and the degradation of seas and oceans. This translates, for example, into a warming of the Mediterranean Sea which causes the installation of exotic marine species in ecosystems, and massive mortality of species. Seen from this angle, the countries that have degraded the climate are responsible. However, this should not absolve countries of their national responsibilities: overfishing, the use of non-conventional fishing gear, the lack of control of pollution on land are the responsibility of each country.



This story was produced with support from Internews' Earth Journalism Network. It was first published in 15-38 Mediterranée on 22 October 2022 in French. It has been translated to English and lightly edited for length and clarity. 

Banner image: In Annaba, divers from the Hippone Sub association submerge the structure of the artificial reef. Annaba, Algeria 2021 / Credit: Probiom.

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