Scientists marked this West African coral reef as probably dead in the 1960s; underwater drones found it alive more than 50 metres below the sea. After identifying a deep-sea coral garden off West Africa in the 1960s, researchers thought it was dead so didn’t explore it – until now. A mixture of soft corals discovered more than 50 meters below the surface off West Africa’s Benin coast. A deep-ocean coral reef presumed dead for nearly 60 years off the coast of Benin was recently rediscovered and is teeming with life. The historical surveys had identified a possible reef more than 50 meters (164 feet) beneath the surface and declared that it was probably dead. Researches used underwater drones to rediscover that a coral reef in West Africa, once thought to be dead, is actually ‘teeming with life.’ One such deep-water reef off the coast of Benin was first identified in the 1960s. While studying fish diversity in the region to identify. A coral reef long presumed dead has been rediscovered “teeming with life” off the coast of West Africa. A deep-water coral reef off the coast of Benin, West Africa, which was presumed dead for 60 years, has been discovered alive and thriving. In a study published in Frontiers in Marine Science, researchers using advanced sonar and underwater drones revealed a healthy marine ecosystem teeming with life more than 50 metres beneath the ocean surface. A deep-water coral reef off the coast of West Africa that was believed to be dead for six decades has been discovered alive and thriving more than 50 metres below the ocean surface. The forgotten reef was first identified off the coast of Benin during surveys in the 1960s that were searching for good fishing areas. At the time, researchers believed the deep-water reef was dead and stopped investigating it.
A modern expedition by the Coral Reefs Rediscovering and Exploration project in Benin (COREB) returned to the site using sonar and deep-sea imaging technology. Instead of finding a lifeless reef, the team discovered a healthy marine ecosystem filled with fish and coral species, according to a study published in Frontiers in Marine Science.
High-tech breakthrough in the deep
Finding the forgotten reef required working in difficult conditions at sea. Researchers used sonar to scan an 11.5-kilometre section of the seabed where historical records suggested coral structures could be located. After the sonar detected two clear signals that could indicate rock or coral formations, the team deployed an underwater drone along with the National Geographic Exploration Technology Lab’s Deep Sea Camera System. These low-cost autonomous systems are equipped with high-definition cameras and lights inside strong glass pressure housings to capture clear images of the seafloor. Gérard Zinzindohoué, a researcher at the Institut de Recherches Halieutiques et Océanologiques du Bénin and the study’s lead author, described the moment the first video footage appeared.
“It was not an easy field campaign,” Zinzindohoué said. “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 that we were close.” “Next, we surveyed the structures with an underwater drone and the Deep Sea Camera System. That was a big moment for us, because suddenly we could actually see the seafloor,” he added. “I still remember seeing those first images. 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.”
A hidden home for marine life
The site is a mesophotic coral ecosystem, a type of reef that grows much deeper than typical shallow coral reefs. Although these corals still need sunlight to survive, they have adapted to the low-light conditions found far below the ocean surface.
“A mesophotic coral ecosystem lives deeper than the usual shallow coral reefs, in zones where light is much more limited,” Zinzindohoué explained. “Unlike typical shallow reefs, it does not always form a single continuous reef structure. Instead, it can appear as patchy or scattered coral communities spread across the seafloor.” Video footage confirmed that the reef is made up of scattered coral patches growing on rocky parts of the seabed. Researchers identified eight different coral types and eight fish species living within the habitat.
The marine life recorded includes golden African snappers, blackbar soldierfish, Guinean angelfish, West African goatfish, Monrovia doctorfish, three-banded butterflyfish, and two species of damselfish.
Unlocking the secrets of West Africa’s coast
The discovery is the first confirmed record of a living mesophotic coral ecosystem on the continental shelf of the Gulf of Guinea. Researchers believe there could be many more undocumented reefs hidden along the West African coastline. “To our knowledge, this is the first confirmed record of a living mesophotic coral ecosystem on the Gulf of Guinea continental shelf,” Zinzindohoué said. “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. If we were able to find this reef again after 60 years, how many others are still undocumented or simply forgotten? So yes, I do believe there are likely more coral systems out there that we have not documented yet. But we should not assume they are everywhere. Each discovery needs to be confirmed. Without going back into the field, we are really just guessing.”
Scientists have not yet collected physical coral samples, so confirming the exact species will require further testing. It also remains unknown whether the reef was actually dead in the 1960s and later recovered, or whether the original researchers simply misjudged its condition.
Historical records suggest the full coral reef may stretch for about 40 kilometres parallel to the coastline, meaning the team has explored only a small part of the entire structure. “This is still an initial exploration,” Zinzindohoué said. “The historical reports suggested that this could be a continuous coral reef barrier extending roughly 40 kilometers parallel to the coast. We only surveyed a small section of this area and we had a limited number of visual transects. 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 program. These are ecosystems that are still poorly known in this part of the world, and every additional piece of information matters.”
Zinzindohoué said the greatest importance of the discovery is what it could reveal about the region’s ancient oceans.
“For me, the most exciting part is about understanding the reef’s history, and what it can tell us about how the ocean in this region has changed over time,” he said. “It feels like we have only just started to read an archive that has been there for a very long time.”
Key Details of the Discovery
- The Location: Found on the continental shelf of the Gulf of Guinea off the coast of Benin.
Mesophotic coral ecosystems (MCE) remain poorly documented along the West African coastline, particularly on the continental shelf of the Gulf of Guinea. Coral reef barriers were reported off the coast of Benin during studies conducted in 1963-1964, but their ecological status remained unknown and they were presumed dead. Between April and December 2025, exploratory marine surveys combining side-scan sonar mapping and underwater video exploration were conducted to re-evaluate these historical data. Over a surveyed west-east extent of approximately 7 km, side-scan sonar data revealed two spatially distinct zones of elevated acoustic backscatter, interpreted as consolidated hard-bottom structures. Visual observations conducted at selected sonar targets documented living coral communities at depths of 54 m on rocky substrate at discrete locations within the surveyed area along the Benin continental shelf. The assemblage was dominated by octocorals, forming a mesophotic coral garden rather than a structuring scleractinian reef. At least six octocoral morphotypes and two black coral taxa, and eight associated reef fish species were observed from imagery. These observations provide the first confirmed visual evidence of living mesophotic coral communities off Benin and, to our knowledge, the first documented occurrence on the Gulf of Guinea continental shelf. More broadly, this study contributes baseline information for a region where mesophotic ecosystems remain largely unexplored and highlights the need for broader acoustic mapping, quantitative surveys, and physical sampling to better understand the extent and ecological significance of these habitats. Mesophotic coral ecosystems (MCEs) are light-dependent communities typically occurring at depths beyond those commonly accessible through standard recreational diving and extend to the lower limits of reef-building corals constrained by light availability and temperature. This depth, commonly reaching approximately 150 m in clear tropical waters, defines the lower photic zone where reef growth remains possible. Ecologically, MCEs function as transitional systems between shallow reefs and deeper benthic habitats, often harboring distinct species assemblages and environmental conditions compared to shallow-water counterparts. Particularly in the Gulf of Guinea, coral reef research across both shallow and deep habitats is extremely limited, and mesophotic coral communities remain largely undocumented. This region therefore represents a major knowledge gap in global coral reef science, despite its location within the tropical Atlantic.
Coral reefs along the Benin – Togo continental shelf were first identified during surveys conducted in 1963–1964 by the Office de la Recherche Scientifique et Technique des Territoires Outre-Mer (ORSTOM, now Institut de Recherche pour le Développement). These surveys, carried out at the request of the governments of Dahomey (now Benin) and Togo, aimed primarily to map trawlable seabed and document fish diversity. During these surveys, a coral reef barrier was observed at depths of 52–56 m.
Historical Oversight: First identified in the 1960s by fishing surveyors, researchers at the time wrote it off as a lifeless, dead formation and abandoned further investigation. The Thriving Coral Reef That ‘Defeated Time’ in West Africa 60-year mystery has been solved as researchers discover a coral ecosystem on the Benin-Togo continental shelf that is still teeming with marine life. In the 1960s, fishing surveyors off West Africa’s Benin coast hauled up heads of coral in their nets. Employed by local governments to assess fish diversity and discover potentially trawlable seabeds in the sandy-bottomed Gulf of Guinea, the researchers shrugged off the discovery at the time, burying the find in a brief paragraph in a 130-something-page report.
With no surveys since, the scientists who followed had lost track of exactly where the reefs might lie. And as mass bleaching events and overfishing slashed the world’s coral reef area by the 1950s, local oceanographers had written off any remnants of a possible reef as dead.More than six decades on, the mystery has been solved as a team of Beninese scientists rediscovered the healthy reef teeming with marine life. At least eight coral types and eight fish species have formed a thriving ecosystem on this long-forgotten site. A hope that sometimes there are species or ecosystems which kind of defeat time, or are trying to resist it,” said Gérard Zinzindohoué, the project lead for Coral Reefs Rediscovering & Exploration in Benin (COREB).
Fresh off seeing coral for the first time in Cape Verde in 2021, Zinzindohoué asked himself a simple question: Do we have any reefs in Benin?
After a colleague passed on the original 1960s report—which mapped out a potential 24-mile-long coral reef barrier along Benin’s coastline—Zinzindohoué recognized a gap in the scientific knowledge: “I realized how little we know about our own coastal environment.”
But in the years that followed, a string of failed grant applications halted progress on solving the mystery.
When he secured a $20,000 National Geographic Explorers grant in January 2025, the project finally ignited. Yet getting the gear was also challenging. The sonar equipment swallowed up almost 80 percent of the grant budget and nearly stalled entirely when the European supplier refused to accept payment from Zinzindohoué’s African bank account.
To complicate matters further, Benin doesn’t have a permanent research vessel. Zinzindohoué therefore had no choice but to seek the help of local fishermen to ferry the team to the suspected site 14 miles offshore and jury-rig the pirogue to accommodate towing the high-tech sonar device.
“The fishermen’s boats are not used to going that far offshore, so it was risky for everyone,” said Zinzindohoué, whose team battled repeated engine failures and months of nausea-filled fieldwork before finally locating two strong sonar echoes pinging from the depths below. National Geographic—whom Zinzindohoué credits with the success of the project—then dispatched a high-resolution Deep Sea Camera System from their Exploration Technology Lab to investigate the sonar results.
While their wooden pirogue bounced atop the offshore swell, the team filmed the seafloor below but had to wait until they returned to dry land to scour the footage. What they had captured was a wealth of marine life: Six types of soft coral; two black corals; and eight species of sheltering fish, from golden African snappers to the Monrovia doctorfish.
When the first images came through, Zinzindohoué texted Houangninan Midinoudewa, an oceanographic researcher at the Benin Marine Conservation Club and the same friend who first told Zinzindohoué of the 1960s report.
Midinoudewa remembers the moment: “I said, ‘Bro, 60 years later we are now discovering exactly what we have in our water.’ We found it still alive, producing more fish for communities and supporting livelihoods. I was really joyful and really overwhelmed.” While no coral samples have yet been extracted, researchers have classified the site as a mesophotic coral ecosystem (MCE). Such systems are light-dependent communities existing at the lower limits of reef-building corals. At more than 175 feet below the surface, the coral garden they discovered appears patchily scattered on a rocky substrate.
Bridging the gap between shallow reefs and deeper benthic habitats, MCEs are home to distinct species and unique environmental conditions. While scientists are increasingly recognizing their ecological and climatic importance, they remain among the least explored elements of tropical and subtropical marine biodiversity. And this one has real potential to unlock new information about coral history.
“Since it’s an undisturbed marine ecosystem, it can help through carbon dating or paleoclimatic study to tell us which kind of climate system has occurred here in the past,” said Zinzindohoué. “It’s better to know the past to help explain the present, and help know which kind of direction we can take in the future.”Footage from the National Geographic Exploration Technology Lab’s Deep Sea Camera System captures a sea floor rich with marine life. In addition to the blackbar soldierfish, West African goatfish and Guinean angelfish filmed darting through the reef, the discovery presents potential conservation claims for other marine life.
“We will be advocating for its full protection, perhaps by setting up a marine protected area around it,” said Midinoudewa, who specializes in elasmobranchs—the study of sharks, rays and skates.
Midinoudewa is currently submitting an application to designate the area as an Important Shark and Ray Area with the International Union for Conservation of Nature. Based on the knowledge of local fishermen, Midinoudewa is confident the reef is home to sawback angel sharks, silky sharks, brown skates and marbled stingrays.
The team behind the discovery hopes this will spark a wave of similar discoveries in the waters off West Africa, an area of the world underserved by scientific research projects
“I hope the Gulf of Guinea will be a hub for research because we know our resources are being exploited and people [need to] know exactly what we have and why we should care,” said Midinoudewa.
Zinzindohoué agrees: “We don’t need to wait for others to come to our country to show us what is under our sea. We are the ones who must take responsibility.” Underwater drones discover coral reefs off Benin, long presumed dead, teeming with life in search of coral reef barriers which had been detected but not investigated in the 1960s, and were thought to be dead, discovered an apparently thriving ecosystem of deep-water corals. Using sonar surveys to narrow down their search areas and then an underwater drone and trail cameras to investigate, they identified a mesophotic coral garden teeming with species of reef-loving fish and multiple different varieties of coral. The researchers suspect that other as-yet undiscovered reef ecosystems could still be out there.
A missing-presumed-dead coral reef has been found alive and well off the coast of Benin. 1960s surveys, focused on identifying promising fishing areas, flagged a possible deep-water coral reef but assumed it must be dead. Now, using a modern sonar survey and the Deep Sea Camera System provided by the National Geographic Exploration Technology Lab, scientists have found an apparently healthy reef.
“It was not an easy field campaign,” said Gérard Zinzindohoué of the Institut de Recherches Halieutiques et Océanologiques du Bénin
“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 that we were close.
“Next, we surveyed the structures with an underwater drone and the Deep Sea Camera System. That was a big moment for us, because suddenly we could actually see the seafloor. I still remember seeing those first images. 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.”
The unexpected survivor
The historical surveys had identified a possible reef more than 50 meters beneath the surface and declared that it was probably dead. Zinzindohoué and his colleagues reasoned that it could have been a mesophotic coral ecosystem.
“A mesophotic coral ecosystem lives deeper than the usual shallow coral reefs, in zones where light is much more limited,” explained Zinzindohoué. “Unlike typical shallow reefs, it does not always form a single continuous reef structure. Instead, it can appear as patchy or scattered coral communities spread across the seafloor.”
Using the historical surveys as a guide, the scientists surveyed 11.5 kilometers of seabed with sonar. This revealed two signals which could represent reefs. To investigate the most promising areas, the team used an underwater drone and the Deep Sea Camera System, like underwater trail cameras. The footage showed a seemingly healthy reef, with eight different types of coral and eight species of fish sheltering and feeding around the corals: golden African snappers, blackbar soldierfish, Guinean angelfish, West African goatfish, the Monrovia doctorfish, three-banded butterflyfish, and two species of damselfish.
This reef doesn’t seem to be a continuous coral barrier, but patches of coral occupying rocky areas suitable for their growth. However, it’s possible that further surveys will identify more reefs.
“To our knowledge, this is the first confirmed record of a living mesophotic coral ecosystem on the Gulf of Guinea continental shelf,” said 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. If we were able to find this reef again after 60 years, how many others are still undocumented or simply forgotten? So yes, I do believe there are likely more coral systems out there that we have not documented yet. But we should not assume they are everywhere. Each discovery needs to be confirmed. Without going back into the field, we are really just guessing.”
The scientists point out that they haven’t been able to sample the corals directly yet, which means that the species identifications still need to be confirmed. It’s also impossible to know, without more data, if the corals were dead in the 1960s and have since recovered. Much more research will be needed to learn about this reef and other possible reefs nearby.
“This is still an initial exploration,” said Zinzindohoué. “The historical reports suggested that this could be a continuous coral reef barrier extending roughly 40 kilometers parallel to the coast. We only surveyed a small section of this area and we had a limited number of visual transects. 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 program. These are ecosystems that are still poorly known in this part of the world, and every additional piece of information matters.
For me, the most exciting part is about understanding the reef’s history, and what it can tell us about how the ocean in this region has changed over time. It feels like we have only just started to read an archive that has been there for a very long time.”
The scientists point out that they haven’t been able to sample the corals directly yet, which means that the species identifications still need to be confirmed. It’s also impossible to know, without more data, if the corals were dead in the 1960s and have since recovered. Much more research will be needed to learn about this reef and other possible reefs nearby.
“This is still an initial exploration,” said Zinzindohoué. “The historical reports suggested that this could be a continuous coral reef barrier extending roughly 40 kilometers parallel to the coast. We only surveyed a small section of this area and we had a limited number of visual transects. 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 program. These are ecosystems that are still poorly known in this part of the world, and every additional piece of information matters.
For me, the most exciting part is about understanding the reef’s history, and what it can tell us about how the ocean in this region has changed over time. It feels like we have only just started to read an archive that has been there for a very long time.”
The Modern Expedition: The Coral Reefs Rediscovering and Exploration project in Benin (COREB) re-located the site using side-scan sonar mapping and the National Geographic Exploration Technology Lab’s Deep Sea Camera System.
- Corals: At least eight distinct coral types, heavily dominated by octocorals (soft corals) and black coral taxa.
- Fish Species: Eight different species of fish, including golden African snappers, Guinean angelfish, blackbar soldierfish, and the Monrovia doctorfish.
Why This Discovery Matters
This finding marks the first confirmed record of a living mesophotic reef on the Gulf of Guinea continental shelf. Because historical data suggests this coral barrier could span nearly 40 kilometres parallel to the coastline, scientists believe they have only scratched the surface of an enormous, climate-resilient underwater archive.
If you would like to explore this topic further, I can provide more details on how mesophotic corals survive in low-light environments or update you on future deep-sea mapping expeditions planned for the West African coast.
