Scientists placed 23 3D-printed reefs up to 1,100 metres underwater to test whether damaged coral habitats can recover |

Researchers are installing 3D-printed artificial reefs on the deep seabed to see whether damaged cold-water coral habitats can be restored. Twenty-three of these structures have been placed off the south-west Porcupine Bank, off Ireland’s west coast, and in the Bay of Biscay, France. The work forms part of the Horizon Europe project REDRESS, which stands for Restoration of deep-sea habitats to rebuild European Seas. According to the University of Galway, researchers are part of the international team behind the effort. The team wants to learn whether the structures can give corals a place to settle and grow in areas harmed by bottom trawling.

How are scientists testing 3D-printed reefs underwater

The twenty-three artificial reefs were installed as a contribution to REDRESS. The current campaign is part of a three-year mission known as REDECOR, short for REstauration DEs CORaux d’eau froide. It involves collaboration between researchers from the University of Galway, Ifremer and the Sorbonne University in France.The university states that the expedition took place on board L’Atalante, a vessel of the French Oceanographic Fleet, during August. Reefs were placed at depths between 900 and 1,100m off the Porcupine Bank and in the Guilvinec Canyon, Bay of Biscay, where other reefs installed during the 2025 expedition were also monitored. Monitoring of both Irish and French restoration sites is planned next year on board an Irish research vessel.

Why are cold-water coral reefs important for deep-sea biodiversity

Cold-water coral reefs are regarded as less well known than their tropical cousins, but they provide important habitats for marine life and support biodiversity in the deep sea, including fish. The corals are quite fragile and easily damaged by deep-sea trawling. The university notes that recent fisheries and conservation regulations prohibit trawling in many areas where corals are found, and that the issue now is how to return damaged areas to full health.Dr Anthony Grehan, a deep-sea ecologist at University of Galway and co-leader of the mission to the Porcupine Bank, said: “These deep-sea coral reefs provide vital habitat for a diversity of marine life, but many have been damaged over many years. Because these corals grow by only a few millimetres each year, natural recovery of lost reefs can take decades to centuries.”Marie-Claire Fabri, a research engineer in deep-sea benthic ecology at Ifremer and co-leader of the Bay of Biscay region expedition, said: “Preserving these areas alone is not enough; the active restoration of cold-water corals is urgently needed.”

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How are the 3D-printed reefs designed to support coral growth

The artificial reefs are eco-designed cylinders made from low-carbon concrete incorporating volcanic material. Each 3D-printed structure is approximately 80cm high and 100cm in diameter, weighing around 600kg. They provide structurally complex physical microhabitats, including tunnels, ledges and overhangs, that offer shelter and provide surfaces for corals and other marine life to colonise. The reefs are placed individually on the seabed.The university explains that different approaches are being tested. Some reefs were equipped with oyster shells, ceramic plates and tiles to encourage coral larvae to settle naturally, while others were fitted with fragments, known as nubbins, of living coral. These fragments were collected from the ocean at depths of around 950 metres and kept in seawater tanks under conditions designed to replicate their natural environment. Small branches were then taken from the colonies and attached to oyster shells before being anchored on the artificial reefs. The team is focusing on the two principal reef-forming species of cold-water coral, Lophelia pertusa and Madrepora oculata.

What marine species have colonised the artificial reefs

Researchers found that the coral nubbins placed on the artificial reefs during the REDECOR 2025 mission are still alive. The reefs have also been colonised by a range of marine species, including sea urchins, fish, crabs and crinoids. Researchers will monitor the sites over the coming years through photography, video and 3D mapping, and will also monitor seawater conditions, sediment and chemical contaminants. The university says this will help improve understanding of the conditions needed for healthy coral growth and assess the potential impact of climate change and ocean acidification on restoration efforts.Dr Grehan said: “The early results are very encouraging, and if we can show that these approaches work, it could open up new possibilities to scale up the restoration of damaged coral reefs elsewhere in the Atlantic and beyond.” According to the university, both restoration sites are now protected from bottom trawling. The SW Porcupine Bank site is protected under the European Common Fisheries Policy, where trawling is prohibited at depths greater than 800 metres, and the Guilvinec Canyon is a Natura 2000 site where trawling is also prohibited. REDRESS brings together 27 partners from 15 countries, and partners from the UK, Iceland and Italy have installed the same reef modules in their own restoration sites. The researchers expect the results to help inform implementation of the new European Nature Restoration Law.