“When you ask people what is under the sea, many imagine sand, rocks, fish, but it's hard for them to think of a forest or a meadow,” points out Aurora Ricart, also a researcher at ICM-CSIC and junior group leader at La Caixa.Under the coastal waters, between the shore and about 20 meters deep, seagrass meadows extend. A few meters further down, macroalgae forests begin to appear, which can reach up to 40 or 50 meters. And from 15 or 20 meters deep and up to more than 100, it is when these animal forests emerge, full of color, with corals, gorgonians, sponges, bryozoans.All three, despite being different coastal ecosystems, share a fundamental characteristic: they build the architecture of the sea. “If these structural species disappear, all the species associated with them vanish,” warns Ricart, who reiterates: “It's like removing buildings in a city or trees in a forest.”
The guardians of the underwater forests to the rescue of the Mediterranean
Catalan scientists drive pioneering projects to restore the biodiversity of the seabed that sustains coastal life
This browser does not support the video element.
Even in the middle of the morning, activity at the fishermen's guild of Blanes is frantic: a coming and going of boxes full of anchovies and sardines, and mullets and other fish, arriving at this Girona fish market for auction. Unaware of this bustle and sheltered under the piers, about forty individuals rest, impassive, in enormous water tanks. Some have been there recently and are recovering, waiting for their moment to come. Others are already prepared and will return to the sea soon.
Most are gorgonians, beautiful colored sea fans that resemble trees; there are also other species of corals, sponges, some curious sea feather, and bryozoans. Not long ago, all these invertebrate animals lay at the bottom of the Mediterranean, at depths of tens of meters, forming part of veritable three-dimensional underwater forests, where fish and crustaceans find refuge, food, and places to reproduce.
Accidentally, however, at some point they became trapped in fishing nets, which tore them from the seabed. Years ago, they would have ended up dead on the dock or thrown back into the sea without any possibility of survival. Today, however, their fate is, fortunately, different.
La Marina takes an example from the first water tank, a kind of saltwater ICU at 13°C. Very carefully, she observes it, admires it, and places it on a slate with a ruler drawn on it. “It is an Eunicella cavolini, an orange gorgonian, very delicate. If we keep it out of the water for too long, it turns black,” she explains. Sofia nods, takes a photo of it, and enters it into the registry of recovered species. Quickly, they put it back in the aquarium. It is one of the last individuals brought by the fishermen of Blanes. “When they catch one, they notify us through a WhatsApp group we have, and they bring it here, to the aquarium,” they tell us.
Both Marina and Sofia are doctoral students at the Institute of Marine Sciences (ICM-CSIC) and have been visiting fishing cooperatives along the Catalan coast for three days. They started in Llançà, then visited those in Port de la Selva, Cadaqués, Roses, Palamós, and Sant Feliu de Guíxols, and today they have arrived at the one in Blanes. End of the journey. In two weeks they will start again, doing the same route. Meanwhile, another team from the University of Barcelona will be in charge of the animals in the aquariums installed in the fishing cooperatives of Arenys de Mar and Vilanova i la Geltrú.
Once these organisms have been recovered, they are attached with a special resin to pebbles to ensure that, when they are thrown back into the sea, they will remain upright. They have named it the badminton method and this, Sofia and Marina assure, contributes to their survival, because "if they are left overturned they suffocate". When fishermen go out to fish, they take them and return them to some of the fishing grounds distributed along the Catalan coast. When they do, they send them a photo and GPS coordinates, so that scientists can track them.
First conserve, then restore
This scene, of recovering accidentally captured animals, taking care of them to then return them to their habitat with the necessary conditions to guarantee their survival, summarizes a profound paradigm shift in marine conservation. Because if for decades efforts were concentrated on protecting ecosystems to prevent them from degrading due to human action, scientists now assume that this is no longer enough and are working against the clock to rebuild them. The titanic challenge is how to do it.
In fact, this is what the European project Life ECOREST, coordinated by the ICM-CSIC, which since its launch in 2022 has already managed to return around 10,000 animals to the Mediterranean in collaboration with Catalan fishermen. The aquariums we have just visited in Blanes are part of it.
“We carry out monitoring campaigns of these actions that have allowed us to know that more than 90% of the animals we reintroduce survive and that the habitats we restore act again as a refuge for biodiversity”, points out with satisfaction Jordi Grinyó, Beatriu de Pinós postdoctoral researcher at ICM, at the head of this initiative.
The final objective of Life Ecorest, which will conclude next year, is to restore nearly 30,000 hectares of vulnerable deep marine habitats on the Catalan coast.
This idea, in fact, began to take shape more than 30 years ago, when the fishermen themselves realized how various fishing stocks on the country's coast were on the verge of collapse or in accelerated decline. And even then, in collaboration with ICM researchers, they decided to establish the first enclosures, areas completely protected from fishing.
“It is a rather unique fact in the entire Mediterranean, because it has not been an imposition by the administration, but the result of a consensual process with the fishing sector,” assures Grinyó, who highlights that in our country “we have one of the highest densities of reserves”.
The first trials in Roses, where a 50 km² enclosure was established, showed that in just two years fishing recovered. “The biomass of juvenile hake, for example, increased 10 times compared to outside the reserve in two years", says the marine ecologist, who points to the explanation: “It is giving species a space to reproduce and live without pressure”.
The idea of establishing more enclosures along the Catalan coast began to take shape. However, the exploration of those protected reserves with underwater robots showed that sessile fauna, the kind that lives attached to the seabed, which forms true forests that are home to biodiversity, was not recovering at the same rate as some commercial species that had been evaluated. This led to the launch of Life Ecorest, in which 8 Catalan confraternities currently participate.
“We see how many species use these restored organisms to lay their eggs. We have seen gorgonians that we had returned to the sea completely covered in catshark eggs, egg masses of cephalopods, and juveniles of other species among the branches,” the ICM-CSIC researcher adds, summarizing four years of the project's operation.
The success of the Life Ecorest experience is proof that restoration can recover not only organisms but also the ecological functions of the system. And it has already inspired similar actions in other parts of the State, such as the Balearic Islands, Valencia, and Galicia, and they will now launch a similar project in Cadiz. In the Azores and Mexico, they are applying the same methodology but at greater depths, of 400 meters.
For a good part of the 20th century, the main problem for Mediterranean forests was water pollution. The construction of treatment plants allowed the stabilization of many seagrass meadows that had been receding since the 1960s. Now the challenge is different: “Every year we break temperature records”. Marine heatwaves have become a growing threat to organisms that cannot move to seek cooler waters.Aurora Ricart, junior group leader 'la Caixa' at the Institute of Marine Sciences (ICM-CSIC), investigates how human action and the warming of the Mediterranean affect these coastal ecosystems. In aquariums at the ICM, located in front of Barceloneta beach, they conduct experiments with macroalgae to find out how they will respond to future climate situations.“Species have survival thresholds and when certain temperatures are exceeded they cannot survive,” she states, giving the example of the heatwave that between 2014 and 2016 killed 90% of the population of giant kelp forests in some areas of California.In the Mediterranean, researchers already detect local mortality and know, thanks to laboratory experiments, that many species are approaching their physiological limits. Posidonia, for example, begins to show signs of stress when the water temperature exceeds 26 °C, a value that is already commonly reached during the hottest summers.Furthermore, to this invisible enemy we must add other old acquaintances: pollution, bottom trawling, boat and ship anchors, and port construction, which involve physical alteration of the space.
Restore the ecosystem
The aquariums distributed by Catalan fishermen's guilds will not on their own reverse decades of Mediterranean degradation, but they symbolize a major challenge. “For many years we thought that conserving was enough. But we were wrong,” states marine biologist Emma Cebrian from the Blanes Advanced Studies Center (CEAB-CSIC), one of the pioneers in restoration, emphatically. “No one questions that after a fire a forest needs to be restored. With the sea, we must begin to think the same way”.
However, restoring, Cebrian insists, goes far beyond replanting. "It involves improving water quality, to have few invasive species, managing moorings and fishing, among other things. Planting is the last action and must be done strategically".
It is in this sense that Cebrian began working 15 years ago on macroalgae forests, which are her specialty. With her research group, she managed to restore Cala Teurela, in the bay of Maó, in Mallorca, a forest of cystoseira algae at a point where it was documented to have existed at the beginning of the last century and which had disappeared due to pollution. It was a years-long project with which they managed to recover biodiversity, and the processes of oxygen production and carbon capture. An extraordinary feat, because once forests, whether of corals, gorgonians, or macroalgae, are lost, it is extremely difficult to recover them.
Unfortunately, it remains, for the moment, the only successful example. “Planting organisms where they have been lost does not guarantee the recovery of an ecosystem and its ecological functioning,” emphasizes the researcher.
And it is that these coastal ecosystems are not just underwater landscapes, but natural infrastructures that sustain a large part of marine life. They oxygenate the water, fix sediments, and help protect beaches from erosion. They act as a refuge and breeding ground for numerous species, including many fish and crustaceans that form the basis of artisanal and commercial fishing. In addition, they concentrate a large part of Mediterranean biodiversity.
That is why, insists Cebrian, “restoring the sea is not an aesthetic issue or an obsession of biologists. It is an investment in quality of life”.
A national plan for marine conservation
Now this marine biologist coordinates the first restoration plan for marine habitats in Catalonia, the Peremcat, a pioneering project in the Mediterranean with an investment of over three million euros from the Department of Maritime Policy and Sustainable Fishing of the Generalitat, which aims to first identify which marine habitats exist, their condition, and the threats they face, in order to then decide on the actions to be taken in each case. "We could not start restoring without a national plan, it would be like starting to build roads and highways without a mobility plan," argues Cebrian.
For the moment, they have divided the Catalan coast into 31 water masses, from Les Cases d’Alcanar to Cap de Creus, and they have already drawn up a map of the existing habitats and their health status. “We have discovered macroalgae forests that we didn't even know existed in Catalonia, which are in very good condition and, therefore, we can still act to maintain them,” states this marine biologist.
They are now working to identify the threats each one faces. “It’s common sense: before restoring, you must eliminate the cause of degradation. It’s useless to replant seagrass in spots where boats continue to anchor, nor to return gorgonians if they will be uprooted again later,” considers the CEAB marine biologist. Each habitat needs a different strategy and priorities will have to be set.
Once what causes degradation has been stopped, one can opt for the system to recover on its own or to carry out an active intervention by reintroducing organisms. “Restoring is not simply planting, but achieving an ecosystem that functions again,” says Cebrián.
This paradigm shift is no longer just scientific, but also a legal obligation. The European Union has approved the Nature Restoration Law, which obliges member states to promote the recovery of degraded ecosystems. Among the objectives is to recover at least 20% of terrestrial and marine habitats of Community interest before 2030. Catalonia is already moving towards this goal. For decades we have tried to prevent the Mediterranean from continuing to degrade. Now it’s time to start rebuilding it.