The National Oceanography Centre REDRESS team (Andrew Gates, Lisa Skein, Veerle Huvenne, Sara Driscoll) deployed 15 ecoreefs to encourage cold-water growth in a restoration experiment on coral ‘mini-mounds’ within The Canyons Marine Conservation Zone, south-west of the UK. The reefs were deployed on the RRS Discovery DY200 expedition between 22 September – 12 October 2025 and included 12 of the REDRESS project’s 3D-printed stacked designs, as well as three ecoreefs donated by the Life Lophelia project. The Canyons Marine Conservation Zone, in the far southwest of the UK EEZ, includes two branches of the Whittard submarine canyon system: the Dangeard Canyon and Explorer Canyon. The area is protected because these canyons support habitats of conservation importance, including cold-water corals, coral gardens, sea pens and burrowing megafauna. It has been closed to bottom contact fishing since June 2022. This makes it an ideal location for restoration efforts within Project REDRESS – fauna of restoration importance is known to be present but in a degraded state, it is protected from further impacts, and it is accessible through existing research and monitoring programmes. The NOC team successfully deployed 15 ecoreefs on ‘mini-mounds’ in shallower areas adjacent to the Dangeard and Explorer submarine canyons (interfluves). The mini-mounds are areas where coral reefs have existed in the recent past. Twelve ecoreefs were of the “wedding cake” type from the company D-shape funded by Project REDRESS and three were ‘star’ shaped donated by the Life Lophelia project (Figure 1).

Deployment sites were carefully selected using high-resolution bathymetry and side-scan sonar data collected with the Autosub5 AUV (Autonomous Underwater Vehicle). We used a stratified random design with 3 reefs of each type deployed on the Dangaerd interfluve, and 3 each of the D-shape reef models on the Explorer interfluve. Candidate mini-mounds for ecoreef deployment on the Dangaerd and Explorer interfluves were first identified using the AUV maps (Figures 2 and 3). Baseline imagery surveys were then conducted along transects over the candidate mini-mounds using a SeaSpyder tow-camera system to characterise current conditions and communities before reefs were deployed. The mini-mounds were specifically targeted as they indicate past coral growth and their height above the surrounding seafloor makes them better locations for promoting coral recruitment. The baseline imagery surveys also included comparable coral mounds where no ecoreefswere deployed, so that future studies can compare their benthic communities and the effects of such restoration efforts in the deep-sea. As part of the baseline characterisation the team also carried out CTD casts, took water samples for nutrient analysis and to characterise the carbonate system (total alkalinity and dissolved inorganic carbon).

The precise placement of ecoreefs onto the selected mini-mounds followed the deployment method developed by our colleagues at IFREMER. The 12 “wedding cake” type ecoreefs were prepared for deployment by routing 5m long, 6mm 7×19 galvanised steel lifting strops through the holes within the body of the reefs. This type of wire was chosen as it was the thinnest and therefore most flexible wire easily available that would be strong enough to lift the reefs whilst complying with lifting regulations. Both ends of the wire strops were attached to the acoustic release hook. One end of each strop was attached with 1.8mm polypropylene line to the shackle above the acoustic release to act as a weak link should a strop become snagged (Figure 4).

The setup for the “star” type reefs was similar except that a webbing strop was used instead of the steel wires as the risk of snagging was much less. The strop was routed through the lifting point, one end was attached to the acoustic release hook and the other end attached to the shackle connecting the acoustic release to the ships wire. The reefs were lowered to the seabed and released using acoustic release. A USBL beacon was clamped to the wire 20m up from the end to provide accurate deployment position information. When the reefs were lowered to ca. 10m above the seabed, small adjustments were made to their position by moving the ship on DP (Dynamic Positioning). Active heave compensation on the winch was used to ensure a gentle landing on the seafloor. All the reefs were successfully deployed, intact and with no hardware being left on the seabed, confirmed through a subsequent tow-camera survey (Figure 5).

The ecoreefs will now be left in situ and will be monitored in the coming years through a combination of opportunistic surveys (ad-hoc towed camera surveys on cruises of opportunity) and dedicated ROV-based surveys every 3 to 6 years, starting in 2028, as part of the NERC-funded National Capability programme AtlantiS and its successors.