Deep Diving and Innovation to Restore the Gulf's Mesophotic Corals

Deep in the Gulf of America lies a vital but little-known habitat. In the "mesophotic" (middle light) zone are coral ecosystems that are essential to the Gulf's food web. In 2010, the Deepwater Horizon oil spill injured extensive areas of this delicate environment. Today, scientists across federal agencies and partner organizations are working together to restore these foundational habitats.

In the spring of 2026, a mission on board NOAA Ship Nancy Foster set out to achieve ambitious restoration goals. The team focused on planting propagated corals of species Swiftia exserta, Muricea pendula, and Thesea nivea , and collecting samples to better understand the seafloor and local water quality. Some of the corals were planted on new dome-shaped concrete structures . They were specially designed by Marine Applied Research and Exploration to support coral growth and provide habitat for other small marine animals.

New Innovations to Streamline Outplanting

Getting the corals safely down to the bottom is a challenge. In the past, scientists used " coral elevators ." These large, weighted platforms can be lowered from the ship to the seafloor where a remotely operated vehicle can then move the corals into place. However, these were cumbersome to maneuver, and met significant resistance as they moved through the water. Plus, it's hard for an ROV, or remotely operated vehicle, to precisely place individual coral fragments on the new dome structures. This challenge called for a new way to transport the corals from the surface down to the bottom, and required the use of human divers to plant them precisely in their intended place.

This mission saw the debut of the "coral torpedo," an invention by Chris Gardner, fisheries biologist with NOAA's Southeast Fisheries Science Center. Designed with a streamlined shape, it travels quickly through the water column. It acts much like the pneumatic tubes at a drive-through bank teller window to deliver precious coral cargo to the seafloor efficiently and safely.

"We were looking for a way to rapidly get corals to the bottom without a lot of water mixing," explains Gardner. "The key is to land them in a very precise location. The corals coming from the lab have little bases on them, so we can just pop them in the tube, then at depth the divers have it set up like a little coral buffet that they can pull from and place on the seafloor. This was definitely a prototype, and I have to say it worked even better than expected."

The new equipment worked flawlessly-safely delivering the delicate specimens down to the divers below. There, the divers made quick work of placing these corals at the designated restoration site.

The Art of Deep-Sea Diving

Divers transition from the Nancy Foster to a smaller support vessel for deployment. This boat's enhanced maneuverability simplifies the process of getting the dive team into the water and onto the site. Once they've navigated to their target location, the divers don their gear and flip backwards over the gunnel and down into the water. The journey to the bottom is quick, unlike the ascent that awaits them at the end of their dive. The trip back up takes a long time, as divers have to stop at multiple depths for several minutes at a time. This allows their body tissues to off-gas, removing nitrogen from the body to prevent decompression sickness.

Reaching these depths is most safely accomplished by specialized technical diving using closed circuit rebreathers, which allows divers to stay down longer. Rebreathers recycle the divers' breathing gas, scrubbing out the carbon dioxide and adding small amounts of pure oxygen to maintain safe breathing mixtures. This system maximizes bottom time and minimizes risks to the divers. It is a demanding discipline that requires extensive training and precise safety protocols overseen by NOAA's Diving Program . On this immensely collaborative mission, technical divers physically navigated the seafloor to carefully place corals into their new homes. To ensure safety at these limits, the team included a hyperbaric physician to monitor the health of the divers once back on board the ship.

Technical divers from the following organizations assisted with this mission:

• NOAA Diving Program
• Moody Gardens
• NOAA Office of Habitat Conservation
• NOAA Southwest Fisheries Science Center
• Florida Atlantic University

A Highly Successful Mission

This combination of advanced technology and skilled diving resulted in several important milestones for the project. This was the first time divers outplanted lab-reared mesophotic corals, and the first time rebreather divers propagated corals in the water.

Mission achievements included:

• Successfully completed decompression dives reaching 72.5 meters (237 feet)
• Successfully outplanted 26 mesophotic corals onto artificial domes at 66 meters
• Relocated 16 coral fragments in the field to start new colonies on domes
• Collected 48 sediment cores to analyze the biology and chemistry of the habitat
• Gathered 51 live biological samples for ongoing study of coral genetics and reproduction
• Sampled 11 coral colonies using non-extractive methods to calculate age and growth rates
• Mapped more than 14 square nautical miles of the seafloor using multibeam sonar
• Engaged the public via livestream events , with a record-breaking audience of more than 100 concurrent viewers
• Collected nine bottles of water samples to analyze for organic matter and environmental DNA
• Deployed and recovered three hydrophones to see how habitat sounds may correlate with coral settlement
• Used diver-deployed stereo cameras to record a video survey of coral sizes in the field-data from which can be compared to lab samples to estimate age and reproduction capacity of the coral communities

While this mission is complete, the restoration work is still ongoing. The team plans to return to continue monitoring the corals' growth and continue supporting the recovery of this deep, complex ecosystem. This successful mission is a prime example of how collaboration and creativity can come together to further restoration of vital mesophotic coral habitats.

This expedition was part of the Deepwater Horizon Mesophotic and Deep Benthic Communities Restoration projects , which are being led by NOAA on behalf of the Deepwater Horizon Open Ocean Trustee Implementation Group to restore injuries caused by the Deepwater Horizon oil spill .