In the 1960s, scientists looking for potential fishing areas off the coast of Benin, West Africa, found what they thought was a deep-sea coral reef more than 50m below the surface. They assumed it must be dead so didn’t investigate further.
But when experts from the Coral Reefs Rediscovering and Exploration project in Benin (COREB) returned to the same site in 2025, they found that quite the opposite is true: this long-forgotten reef is thriving. The discovery is published in Frontiers in Marine Science.
The study’s lead author Gérard Zinzindohoué, a researcher at the Institut de Recherches Halieutiques et Océanologiques du Bénin, and colleagues set out to find this reef barrier because they wondered if it might be mesophotic coral. These are corals that need light to survive but live in deeper waters where there isn’t as much sunlight.
“Unlike typical shallow reefs, it does not always form a single continuous reef structure,” says Zinzindohoué in a statement. “Instead, it can appear as patchy or scattered coral communities spread across the seafloor.”
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In 2025, the researchers used sonar to survey an 11.5km area of seabed where the previous researchers had spotted the potential patches of coral. There, they saw what looked like possible reefs.
To get a clear picture, they used an underwater drone and the National Geographic Exploration Technology Lab’s Deep Sea Camera System. These are “low-cost autonomous systems [that] combine a high-definition camera and lights inside of a glass pressure housing, to capture high-quality imagery of biodiversity on the seafloor,” according to the National Geographic Society’s website.
“That was a big moment for us, because suddenly we could actually see the seafloor,” says Zinzindohoué.
That was a big moment for us, because suddenly we could actually see the seafloor
And sure enough, the reef appeared before them. “I still remember seeing those first images,” he says. “It was a mix of excitement and disbelief, because after all this time thinking about this reef, suddenly there was something real in front of us.”
“To our knowledge, this is the first confirmed record of a living mesophotic coral ecosystem on the Gulf of Guinea continental shelf,” says Zinzindohoué. “However, I think what we found is probably not an exception. It is more likely a reflection of how little we still know about coastal regions in West Africa and elsewhere.”
Although humans had next to no idea it was there, this coral garden – which experts had assumed was dead in the 1960s – was healthy and full of life. The researchers recorded eight different types of coral and eight species of fish, including types of damselfish, butterflyfish, snappers, soldierfish, angelfish and goatfish.
Zinzindohoué thinks there could be more like it, waiting to be discovered. “If we were able to find this reef again after 60 years, how many others are still undocumented or simply forgotten?” he adds. “I do believe there are likely more coral systems out there that we have not documented yet.” To find out, the researchers will need to keep looking in other areas.
If we were able to find this reef again after 60 years, how many others are still undocumented or simply forgotten?
They also want to learn more about these corals by surveying a larger area (they were only able to investigate a small part of the barrier from the historical reports) and taking samples of the corals to confirm which species they are.
“If I had all the grant money in the world, the first thing I would do is return to the site with a proper scientific diving and sampling programme,” he says. “These are ecosystems that are still poorly known in this part of the world, and every additional piece of information matters.”
Zinzindohoué is excited about what they have yet to discover about these corals and their history, saying: “It feels like we have only just started to read an archive that has been there for a very long time.”
Image and video credit: Gérard Zinzindohoué, with thanks to support from the National Geographic Society and the National Geographic Exploration Technology Lab
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