La Herradura restores 1,300 colonies of orange coral with a project unique in the world

Punta de la Mona is a museum unlike any other. This beach in La Herradura is home to an underwater art gallery that is unequalled in its diversity and also in need of repair.

Its orange coral (Astroides calycularis) is one of its greatest treasures, a species that two million years ago was widespread in the western Mediterranean, but is now found only in the Alboran Sea and some areas of France and Italy. The coral is included in Spain's national catalogue of endangered species with the category of vulnerable.

Despite Punta de la Mona seabed and cliffs being considered special areas of conservation (ZECs), these marine animals face numerous threats. They end up trapped by the nets and lines of fishermen. They become detached during storms. They are suffocated by the arrival of invasive species such as Asian algae. The increase in sea temperature weakens them to the point that they become white like skeletons... There are many dangers that threaten their survival in the sea. However, a pioneering programme in Spain and the world has managed to bring life back to the seabed with the implantation of at least 1,300 colonies, 60,000 coral units, in four artificial gardens of up to eight square metres underwater.

Asociación Hombre y Territorio (HyT), a non-profit organisation with 20 years of experience in the study and conservation of the natural environment, and the collaboration of Imagin, a platform promoted by CaixaBank, are behind this project that has brought life back to the reefs of the Costa Tropical.

The organisation rescues and transplants uprooted corals to other areas and has developed new techniques to reproduce the animals and generate small populations in an environment where they can survive.

Reporters from Granada newspaper Ideal accompanied the scientists reccently at the launch of the programme and their work to 'build' the reefs, with the help of oceanographer Gador Muntaner and underwater photographer Rafael Fernández. In a boat, the group of scientists and journalists set off from Marina del Este to the coves of Punta de la Mona to witness the 'planting' of corals in the underwater gardens.

Corals reproduce asexually; when they fragment they form cuttings that can continue to grow under optimal conditions. But they also reproduce sexually. There are polyps that produce male gametes and polyps that produce female gametes, which come together to form coral larvae. The larvae find a reef on which to settle to become polyps and form coral colonies that continue to grow.

The group of experts and marine biologists have been studying the behaviour of corals for years to 'assist their reproduction' and since January they have been transplanting and reproducing the coral, helping the larvae to settle in a suitable place, in the four artificial gardens they have created between 10 and 14 metres underwater, and to form colonies.

"What we do is capture and collect these larvae from the coral with pipette and we transport them to other areas to plant them on the reef. They are like seeds; these larvae have a greater potential to establish themselves in the spaces that we have conditioned," explain biologists Alexis Terrón and David León (MedCoral).

Corals reproduce sexually in a very short period coinciding with the first full moon in June. According to experts, they harbour a protein that signals their synchronised release so that they have a better chance of attaching. The larvae have many predators and these organisms have a massive reproductive system to ensure greater survival. When the temperature rises to between 18 and 20C, they prepare to release the larvae.

"By feeling the polyps and observing the coral we know if they are ready. Their activity is monitored day by day as the time approaches. When the larvae are in the tentacles, we take action," they say. This phase generally lasts two weeks, although it can last up to 20 days. "We usually have a team of at least four people, two collect the larvae and two others provide support," says Terrón.

The first signs of successful reproduction are soon evident. Under normal conditions, the larva, which is like an elongated orange grain of rice, searches for a suitable substrate and attaches itself.

When it finds its place, it sticks together like plasticine and forms an orange-coloured ring. In the first few days, the tentacles and polyps that form the colony are already visible, say the scientists. MedCoral saves the larvae the journey and inserts them into the artificial reef they have created at Punta de la Mona.

When the organisation arrived in 2020 at the La Herradura reef where they operate, there were two colonies. In January 2023, they began transplants and put their reproduction techniques into practice until they achieved these 1,400 coral colonies.

"The programme is infinite. Our way of life is making it worse and worse, if we do this right we, our children and grandchildren will be planting coral. We can no longer change our lifestyle, but we can change the way we impact our environment," says Terrón.

"All this stemmed from the research carried out at the Seville aquarium. It was the first step; we took the larvae from the Maro-Cerro Gordo site to study them in the laboratory because it is more complicated in the sea. The first colonies from these trials are now transplanted on the reef and it has been a success. With our harvesters and planters, everything is now planted under the sea in the same session without going through the aquarium," says the MedCoral team.

The genetic variety of the new animals and the gardens or artificial reefs in which they are forming help to prevent invasive algae, which have already settled on the seabed of the Costa Tropical in Granada province, from establishing themselves. The substrate of the artifical reef is hostile for them and they pass by.

Unfortunately, for the moment there is nothing more that experts can do to stop the advance of the invasive algae; it is hoped that the Mediterranean ecosystem will fight and regulate itself to adapt to this threat. The interest in this orange species of coral is not only related to supporting the survival of the species, but also to its characteristics as a driver of marine biodiversity. The colonies attract other animals and contribute to the richness of the ecosystem. In addition, corals have active ingredients for curing certain diseases and are an important part of scientific research.