Scientists have rediscovered a thriving deep-sea coral reef off the coast of Benin, long presumed dead, using advanced sonar and underwater drones, according to research published in Frontiers in Marine Science.
More than six decades after initial surveys hinted at a coral reef off Benin’s coast, researchers have confirmed its existence as a healthy mesophotic ecosystem, revealing a vibrant underwater world in the Gulf of Guinea. The discovery, led by Gérard Zinzindohoué of the Benin Fisheries and Oceanological Research Institute, challenges assumptions about marine biodiversity in the region and highlights the resilience of deep-sea coral systems.
Rediscovery of a Lost Ecosystem
The reef was first detected in the 1960s during fishing surveys, which noted coral fragments in nets but dismissed the site as dead due to limited technology and focus on shallow-water ecosystems. Decades later, Zinzindohoué and his team used high-resolution sonar, an underwater drone, and the National Geographic Exploration Technology Lab’s Deep Sea Camera System to locate and document the ecosystem. The first thing that gave us hope was our first deployment of the sonar. We were seeing nothing but sand and sediment, and suddenly we could see some rocky structure,
Zinzindohoué said, describing the moment of discovery.
Underwater imagery confirmed the presence of eight coral types and eight fish species, including golden African snappers and Monrovia doctorfish, thriving in the “twilight zone” of the ocean. Unlike shallow reefs, this mesophotic ecosystem is scattered across rocky outcrops rather than forming a continuous barrier. A mesophotic coral ecosystem is a type of coral habitat formed deeper than the usual shallow coral reef, in a zone where light is much more limited,
Zinzindohoué explained.
The findings, published in Frontiers in Marine Science, mark the first confirmed living mesophotic coral ecosystem on the Gulf of Guinea’s continental shelf. However, researchers caution that the reef’s history remains unclear—whether it has persisted since the 1960s or if it has waxed and waned over the years.
Challenges in the Search
The expedition faced significant logistical hurdles. Zinzindohoué secured a $20,000 National Geographic Explorers grant in January 2025, but nearly 80% of the budget was consumed by sonar equipment, and a European supplier initially refused to process payments from his African bank account. The fishermen’s boats are not used to going that far offshore, so it was risky for everyone,
he said, describing the reliance on local pirogues to transport gear. The team endured engine failures and months of fieldwork before detecting sonar signals from the seafloor.
Upon returning to land, the team analyzed footage from the Deep Sea Camera System, capturing the first visual evidence of the reef. We found it still alive, producing more fish for communities and supporting livelihoods,
Zinzindohoué recalled.
Significance of the Find
The reef’s survival offers critical insights into marine resilience. The site’s potential to inform climate history and coral adaptation is significant, given the global decline of coral reefs due to bleaching, overfishing, and warming oceans.
While no coral samples have been extracted yet, the team classified the site as a mesophotic coral ecosystem (MCE). Such systems, which exist at the lower limits of reef-building corals, remain underexplored despite their ecological and climatic importance.
Future Research and Conservation Efforts
Zinzindohoué emphasized the need for further research, including direct coral sampling and broader seafloor surveys. To our knowledge, this is the first confirmed record of a living mesophotic coral ecosystem on the Gulf of Guinea continental shelf,
he said. However, he cautioned that the reef’s full extent and historical context remain unknown.
The discovery also underscores the importance of marine conservation in West Africa, where ocean science and research infrastructure are underdeveloped. We hope that, through this result, people will start to look at the ocean differently,
Zinzindohoué said.
As climate change intensifies threats to coral reefs worldwide, the Benin reef’s survival offers a glimmer of hope. Researchers plan to return to the site with advanced sampling tools, while advocating for increased investment in marine science across the region.
The next steps include confirming the reef’s species diversity, studying its response to environmental stressors, and assessing its role in regional fisheries. For now, the rediscovery serves as a reminder of nature’s capacity to endure—and the urgent need to safeguard it.
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