Coral Reef Long Thought Dead Rediscovered Off West Africa — Deep Reef Found Teeming With Life

Researchers have rediscovered a coral formation off the coast of West Africa that was long assumed to be dead and found it "teeming with life." Using modern sonar, underwater drones and the National Geographic Deep Sea Camera System, the team located a mesophotic coral ecosystem more than 50 metres (164 feet) below the surface in the Gulf of Guinea.

The feature was flagged in surveys from the 1960s that were searching for promising fishing grounds and were later concluded to be lifeless. Revisiting those historical records, a research team led by Gérard Zinzindohoué of the Institute of Halieutic and Oceanographic Research in Cotonou, Benin, mounted a modern survey to confirm whether the structure might instead be a deeper, light-limited coral community.

Survey and discovery

Researchers used sonar and underwater drones to find the thriving ecosystem deep below the surface of the Gulf of Guinea. (Gérard Zinzindohoué via SWNS)

Guided by the old charts, the scientists surveyed roughly seven miles of seabed with high-resolution sonar and detected two strong signals consistent with reef structures. They then deployed an underwater drone and the Deep Sea Camera System from the National Geographic Exploration Technology Lab to obtain visual confirmation. The resulting footage revealed patchy coral communities across rocky substrate rather than a continuous shallow reef.

"It was a mix of long days at sea, technical problems, and a lot of uncertainty. But then we saw structures on the sonar that looked like they could be reef signatures, which gave us hope," said lead author Gérard Zinzindohoué. "Suddenly we could actually see the seafloor — it was a mix of excitement and disbelief."

What was observed

The team recorded what appears to be a healthy mesophotic reef hosting eight different types of coral and at least eight species of fish using the visual footage. Fish observed in the imagery included golden African snappers, blackbar soldierfish, Guinean angelfish, West African goatfish, Monrovia doctorfish, three-banded butterflyfish and two species of damselfish.

Surveys conducted in the 1960s, focused on identifying promising fishing areas, flagged a possible deep-water coral reef. But scientists at the time it assumed must be dead. (Gérard Zinzindohoué via SWNS)

Because the researchers were not able to collect coral samples on this expedition, species identifications remain provisional and require direct sampling and laboratory analysis to confirm. It is also unclear whether the formation was truly dead in the 1960s and later recovered, or whether earlier surveys lacked the tools to detect deeper, patchy mesophotic systems.

Implications and next steps

Zinzindohoué and colleagues note that, to their knowledge, this is the first confirmed record of a living mesophotic coral ecosystem on the Gulf of Guinea continental shelf. Historical reports had suggested the possibility of a continuous coral barrier extending roughly 40 kilometres parallel to the coast, but the recent expedition examined only a small section and carried out limited visual transects.

A coral reef long presumed dead has been rediscovered "teeming with life" off the coast of West Africa. (Gérard Zinzindohoué via SWNS)

The team calls for additional fieldwork: systematic mapping, scientific diving where possible, direct sampling and ecological monitoring to determine biodiversity, age, health and vulnerability of the reef. Further surveys may reveal more undocumented deep coastal coral systems in West Africa, underscoring how much remains unknown about these regions.

Publication

Details of the discovery and initial observations are described in the journal Frontiers in Marine Science.