On a recent expedition, restoration experts deployed artificial substrates deeper than 200 ft to help restore mesophotic corals in the Gulf as part of a long-term effort to restore deep-sea habitats injured by the Deepwater Horizon oil spill. These dome-shaped concrete structures, which were specially designed to support coral growth and provide habitat for other small marine animals, represent the most recent phase of testing coral propagation at depth. Future missions will involve technical divers revisiting the domes to outplant coral fragments.
The team deployed six custom-designed domes off the northern Gulf coast of Florida on an expedition aboard the RV Point Sur in June 2025. They used the ship’s A-frame crane to lower each 60-pound concrete dome to the seafloor. The remotely operated vehicle (ROV) Beagle then guided the domes into position near natural coral colonies at sites 65 meters below the surface. Placement locations were carefully selected to maximize proximity and access to large numbers of live corals. The domes were accompanied by temperature loggers embedded within current meters for long-term monitoring of environmental conditions. Following their placement on the seafloor, each structure was photographed from multiple angles for future comparison.
The domes, designed by Marine Applied Research and Exploration in collaboration with the Mesophotic and Deep Benthic Communities (MDBC) Coral Propagation Technique Development (CPT) project, have a realistic rocky structure that provides microhabitats for animals who live on and around coral, also known as coral associates. The domes also have pre-drilled holes designed for quick and efficient outplanting of coral fragments, and stainless steel hardware for easy lifting and movement. The holes are plugged using 3D printed structures that divers will remove to access the holes as attachment points for coral fragments.
This deployment builds on findings from a recent NOAA-led report–the first review of the development and selection of artificial substrates for mesophotic and deep-sea coral restoration. The report highlights the importance of testing materials, design, and placement strategies before large-scale deployment. It also notes that concrete, the material used in the new domes, is an accessible, low-cost, and versatile substrate that could have great potential for coral propagation.
This work within the CPT project is part of the MDBC portfolio, approved to help restore resources injured by the Deepwater Horizon oil spill. After the spill, federal and state agencies formed the Deepwater Horizon Natural Resource Damage Assessment Trustee Council to assess the impacts and implement actions to restore injured habitats, species, and the services they provide. In 2019, the Open Ocean Trustees selected four MDBC restoration projects, one of which was CPT.
The lessons learned from monitoring these domes, combined with additional long-term monitoring data from landers and autonomous reef monitoring structures (ARMS), will help scientists better understand how artificial substrates could supplement coral growth and provide habitat for coral associates. This is part of a larger effort to test many different substrate types, at different depths, and with different coral species, to more effectively implement coral restoration.
This work is being implemented in accordance with the Oil Pollution Act of 1990, which designates the federal and state natural resource trustee agencies that are responsible for representing the public’s interest and acting on behalf of the public to assess and address injuries to natural resources. Funding for this restoration work is mandated by the 2016 legal settlement between British Petroleum and the federal government and Gulf states following the 2010 Deepwater Horizon oil spill in the Gulf of America.
Related links:
- https://www.fisheries.noaa.gov/southeast/habitat-conservation/mesophotic-and-deep-benthic-communities-restoration
- https://storymaps.arcgis.com/stories/908a2d2000894c2b8a6daafb8163a357
- https://coastalscience.noaa.gov/news/spawning-success-scientists-witness-rare-mesophotic-coral-reproduction-in-captivity/