Off Gulf coast of Florida, giant concrete domes were dropped more than 200 feet underwater to help restore corals and sea life. All corals outplanted in 2025 survived and even grew

What looks like an unusual underwater construction project is actually part of a long-term attempt to bring damaged coral habitats back to life. Off Florida’s northern Gulf coast, scientists have been placing specially designed concrete domes more than 200 feet below the surface, creating new foundations where corals and other marine life can settle. The experiment is already showing encouraging results. In a 2026 follow-up mission, researchers found that all of the corals outplanted at one Gulf site in 2025 had survived and even grown.

Why are scientists putting concrete domes on the seafloor?

The project targets mesophotic corals, which live in the ocean’s “twilight zone”, where sunlight becomes increasingly limited. These deep-water communities were among the habitats affected by the 2010 Deepwater Horizon oil spill. NOAA says the spill injured more than 770 square miles of seafloor habitat in the Gulf. The restoration programme is now testing ways to help these ecosystems recover.

In June 2025, scientists aboard the RV Point Sur deployed six custom-made concrete domes off Florida’s northern Gulf coast. Each dome weighed about 60 pounds and was lowered to the seafloor at a depth of approximately 65 metres (213 feet). A remotely operated vehicle then guided each structure into position near naturally occurring coral colonies.

The domes are designed to become new marine homes

The dome structures were designed to resemble rocky terrain and contain small spaces that can provide shelter for animals living around coral. They also have pre-drilled holes where coral fragments can later be attached. Stainless-steel hardware allows the structures to be lifted and repositioned, while temporary 3D-printed plugs cover the attachment points until divers are ready to use them. NOAA said concrete was selected because it is an “accessible, low-cost, and versatile substrate” with potential for coral propagation. That could be important if scientists eventually determine that artificial structures can be deployed more widely without harming surrounding habitats.

Scientists get an encouraging sign from 2025 coral outplants

The biggest breakthrough came not from the domes alone, but from monitoring corals that had already been returned to the seafloor. In 2025, researchers outplanted 24 coral colonies from a laboratory in Galveston, Texas. The team returned in 2026 to check how the colonies were doing. At a site north of Geyer Bank, the results were particularly promising: every coral placed there in 2025 survived and grew. The finding is significant because mesophotic corals are slow-growing organisms and restoring them in their deep-water environment presents major logistical challenges.

How scientists get corals more than 200 feet below the surface

Working at these depths requires specialised equipment and carefully planned dives. During the 2026 restoration work, NOAA and its partners used remotely operated vehicles, technical divers and a specially designed “coral elevator” to transport coral fragments to the seafloor. NOAA Fisheries reported that the 2026 mission successfully placed 26 mesophotic corals on artificial domes at 66 metres, while 16 additional coral fragments were relocated to start new colonies. Scientists also collected sediment and biological samples and mapped more than 14 square nautical miles of seafloor. The work involves NOAA, the U.S. Geological Survey, the University of Rhode Island and Marine Applied Research and Exploration.

Long-term attempt to rebuild gulf’s hidden ecosystems

The successful coral survival is encouraging, but scientists are not presenting it as proof that the restoration challenge has been solved. The teams plan to keep returning to the sites to measure coral growth and monitor how artificial structures interact with the surrounding ecosystem. Researchers are also testing different substrates, depths and coral species to determine which approaches work best. The broader restoration programme began after the Deepwater Horizon disaster and is funded through the settlement reached between BP and the federal government and Gulf states.

For an ecosystem damaged more than a decade ago, the sight of laboratory-raised corals surviving and growing back on the Gulf seafloor offers a rare piece of good news. The concrete domes may be small compared with the scale of the ocean but scientists hope they can become the starting points for much larger underwater communities.