A deep-ocean coral reef that was assumed dead for almost 60 years was recently rediscovered off the coast of Benin and is teeming with life. A team of oceanographers led by Gérard Zinzindohoué at the Institut de Recherches Halieutiques et Oceanologiques du Bénin documented their findings in the journal Frontiers in marine scienceswhich highlights how much there is still to learn about West Africa’s underwater ecosystems.

Scientists first identified the possible location during the 1960s, while studying possible fishing grounds, but assumed that any reef residing along the seafloor was dead. After receiving a grant to revisit the area, Zinzindohoué and his colleagues spent days searching more than seven miles of the Gulf of Guinea using sonar equipment before finally detecting two signatures large enough to match possible reef debris.

“It was not an easy field campaign,” Zinzindohoué recalled in a statement. “It was a mix of long days at sea, technical problems and a lot of uncertainty.”

Zinzindohoué’s team then deployed an underwater drone and the National Geographic Exploration Technology Laboratory’s deep-sea camera system for a closer look. About 165 feet below the ocean’s surface, they saw the unexpected: The reef was far from dead.

“I still remember seeing those first images. It was a mix of excitement and disbelief, because after so much time thinking about this reef, suddenly there was something real in front of us,” Zinzindohoué said.

Deep water reef near Benin

Based on the depth, the team determined that the formation was a mesophotic coral ecosystem. These ecosystems generally exist in much deeper waters than typical shallow coral reefs. With more limited sunlight, mesophotic coral does not necessarily grow as a single, continuous reef. Instead, it takes the form of more irregular or more intermittent colonies.

However, that does not mean that there is little activity in the mesophotic systems. The underwater study identified eight types of coral and eight different species of fish living among them, including the Guinea angelfish (african holacanthus), golden African snappers (Lutjanus fulgens), and the Monrovia doctor fish (Acanthurus monroviae).

Zinzindohoué believes his discovery is the first confirmed living mesophotic coral on the continental shelf of the Gulf of Guinea, but that doesn’t mean it’s the only one.

“I think what we found is probably not an exception. It is more a reflection of how little we still know about the coastal regions of West Africa and elsewhere,” he added.

At the same time, new visits are needed to better examine the delicate ecosystems and confirm their health, diversity and size. Historical data indicates that they only imaged a small portion of a continuous mesophotic reef that extends for almost 40 kilometers parallel to the coast of Benin.

“If I had all the grant money in the world, the first thing I would do is return to the site with a proper diving and scientific sampling program,” Zinzindohoué said. “These are ecosystems that are still poorly understood in this part of the world, and every additional piece of information is important.”

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