A rich coral ecosystem has been discovered in an area that was deemed a 'dead coral reef' 60 years ago.
A survey conducted in the early 1960s concluded that structures believed to be coral reefs off the coast of Benin in West Africa were 'dead,' but a re-examination using the latest technology has confirmed a rich ecosystem inhabited by diverse corals and fish.
Rediscovery of mesophotic coral ecosystems on the continental shelf of the Gulf of Guinea (Benin, West Africa) after 60 years | Frontiers in Marine Science
Coral Reefs Presumed Dead Have Been Found Teeming With Life | ScienceAlert
https://www.sciencealert.com/coral-reefs-presumed-dead-have-been-found-teeming-with-life
The area studied was the seabed approximately 54 meters below the surface off the coast of Benin in West Africa. When fisheries surveys were conducted in this area in the 1960s, only dredging surveys, which involved removing sediment from the seabed, and early sonar observations were available, and researchers concluded that 'coral reefs exist but have already died.' For the next 60 years, no detailed surveys had been conducted in this area.
A research team led by Gérard Zanzandoue of the Benin Marine Fisheries Institute created a map of the seabed using the latest 'side-scan sonar' between April and December 2025. Side-scan sonar is a device that uses sound waves to visualize seabed topography over a wide area, allowing researchers to understand the relative divisions of seabed sediments and the distribution of artificial reefs over a wide area.
The investigation revealed two promising locations believed to be reefs, and the research team used underwater cameras and remotely operated drones to survey the sites. This led to the discovery of a living coral reef ecosystem.
The research team identified at least six different morphologies of
According to the research team, this coral reef is the first living mesophotic coral ecosystem found in the dimly lit waters at depths of 30 to 150 meters on the continental shelf of the Gulf of Guinea. Furthermore, survey records from the 1960s suggested the possibility of a coral reef extending approximately 40 km along the coastline, but only a portion of it was surveyed this time. Therefore, the research team believes there may be even more undiscovered coral reefs in the surrounding waters.
Zanzandowe said, 'I still vividly remember the first time I saw that footage. I was filled with a mix of excitement and disbelief. I had been thinking about this coral reef for a long time, and suddenly it appeared before my eyes as a reality.'
According to Zanzandowe, much of West Africa's underwater biodiversity remains under-documented compared to regions like Australia, the Caribbean, and Brazil. Therefore, Zanzandowe argues that this discovery is not exceptional, but rather suggests that there may be many undiscovered and unexplored coral reefs in West Africa and other coastal areas.
On the other hand, due to budgetary and logistical constraints, only one of the two coral reef areas identified by sonar could be visually surveyed during this investigation. Furthermore, the research team explained that since no coral samples were collected during this survey, the species identification is provisional and based on the images. They also stated that while the coral reefs in this area were deemed 'dead reefs' in the 1960s, likely due to the limited observation tools available at the time, it is currently impossible to determine whether the coral reefs confirmed this time have been alive since then or whether they have recovered after a period of decline.
The research team emphasizes the need to include mesophotoreal habitats in regional assessments and marine spatial planning, and states that future research should combine more extensive acoustic mapping, systematic video transects, and physical sampling to focus on the spatial extent, structure, and origin of discovered coral reefs.
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