‘We cannot simply wait for them to recover on their own,’ says Ifremer expert Marie-Claire Fabri.

Scientists are hoping 3D-printed coral reefs can help revive deep-sea habitats destroyed by bottom trawling.

Researchers from the University of Galway, Sorbonne University and the French oceanographic institution Ifremer, are testing 23 artificial reefs placed on the seabed off the south-west Porcupine Bank – 200km off the west coast of Ireland – and in the Bay of Biscay, France.

The tests are a part of a three-year joint collaboration between the three institutions called Restauration Des Coraux d’eau froide (Redecor).

As part of the mission, scientists were deployed on an expedition aboard a vessel from the French Oceanographic Fleet this August, where they placed 3D-printed reefs at depths of between 900m and 1,100m off the Porcupine Bank and in the Guilvinec Canyon, Bay of Biscay.

Despite being considered lesser known than their tropical counterparts, cold-water coral reefs provide important habitats for marine life and support biodiversity in the deep sea. However, these coral reefs are easily damaged by deep sea trawling. And despite a ban on trawling in many coral-rich areas, the fragile habitat requires additional efforts to revive to full health.

“These deep-sea coral reefs provide vital habitat for a diversity of marine life, but many have been damaged over many years,” said Dr Anthony Grehan, a deep-sea ecologist at University of Galway and the co-leader of the mission to Porcupine Bank.

“Because these corals grow by only a few millimetres each year, natural recovery of lost reefs can take decades to centuries.

“With this project, we are testing whether we can actively accelerate that recovery by creating new starter structures for corals to grow on which also mimic reef structure to help re-establish functioning reef habitats.”

Testing artificial reefs as a viable method to revitalise sea life is one of the ways scientists in the bloc are attempting to tackle marine degradation as part of a four-year Horizon Europe project called ‘Restoration of deep-sea habitats to rebuild European Seas’, or Redress.

The artificial reefs are eco-designed cylinders made from low-carbon concrete incorporating volcanic material, University of Galway explained. They are placed individually on the seabed to form a single connected structure covering an area of about half a hectare.

Each 3D-printed structure is around 80cm high and 100cm in diameter and weighs around 600kg. It provides physical microhabitats such as tunnels, ledges and overhangs for corals and other marine life to colonise.

“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,” said Grehan.

The scientists are using different approaches to bring the seabed back to life as part of the research. Some of the seabeds being tested are equipped with oyster shells, ceramic plates and tiles to encourage coral larvae to settle naturally, while others were fitted with fragments of living coral.

These live coral fragments were collected from the ocean at a similar depth to the artificial ones 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 researchers found that the fragments placed on artificial reefs last year are alive and have been colonised by a range of marine species, including sea urchins, fish and crabs.

Both restoration sites are protected from any further damage by bottom trawling, but that is not enough, said Marie-Claire Fabri, a research engineer in deep-sea benthic ecology at Ifremer and the co-leader of the Bay of Biscay region expedition, who called for active restoration efforts.

“The ban on bottom trawling has helped stop the direct pressure on these habitats, but to go further – given the slow growth of these corals in the Atlantic – just a few millimetres per year – we cannot simply wait for them to recover on their own.”

Scientists will continue to monitor these sites over the coming years, and work on better understanding their exact marine conditions to help better replicate the lost habitats.

Redress brings 27 partner organisations from 15 countries to investigate the restoration of damaged deep-sea habitats across Europe. The EU-funded project also has similar artificial reef modules in restoration sites across the Atlantic and the Mediterranean.

Don’t miss out on the knowledge you need to succeed. Sign up for the Daily Brief, Silicon Republic’s digest of need-to-know sci-tech news.