– credit, Gérard Zinzindohoué via SWNS
A coral reef long presumed dead has been rediscovered “teeming with life” off the coast of West Africa.
Surveys conducted in the 1960s that were focused on identifying promising fishing areas, flagged a possible deep-water coral reef, but scientists at the time it assumed must be dead.
Now, using a modern sonar survey, scientists have found an apparently healthy reef—an amazing discovery that was described in the journal Frontiers in Marine Science.
After days of “difficult” field work, the sonar revealed structures which the team interpreted as a coral reef, and hopes were raised.
“It was a mix of long days at sea, technical problems, and a lot of uncertainty,” lead author Gérard Zinzindohoué said of the effort. “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.”
Mr. Zinzindohoué and his colleagues at the Institute of Halieutic and Oceanographic Research in Cotonou, Benin, 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, he explains.
“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 research team surveyed 7 miles of seabed with sonar. To investigate the most promising areas, the team used an underwater drone, and the Deep Sea Camera System, provided by the National Geographic Exploration Technology Lab.
The footage showed a seemingly healthy reef, with 8 different types of coral and 8 species of fish sheltering and feeding around the corals.
The fish included golden African snappers, blackbar soldierfish, Guinean angelfish, West African goatfish, the Monrovia doctorfish, three-banded butterflyfish, and two species of damselfish.
The reef doesn’t seem to be a continuous coral barrier, but patches of coral occupying rocky areas suitable for their growth, although researchers say 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. However, I think what we found is probably not an exception.”
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“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?”
The research team hasn’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 really dead in the 1960s and have since recovered. That would make them intriguing research targets as the study of coral resilience in a changing climate advances.
Mr. Zinzindohoué interprets the historical reports as potentially recording a continuous coral reef barrier extending roughly 40 kilometers, or 24 miles, parallel to the coast.
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“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,” he said.
“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.”
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