Member states of the International Seabed Authority, meeting in Kingston, Jamaica, from July 25 to 28, fiercely debated the issue of deep-sea mining, without being able to agree on a common position. Scientists have been highlighting the risks of mineral extraction for the still little-known biodiversity of the seabed, which represents two-thirds of the planet's surface.

In the Clarion-Clipperton Zone in the Pacific, coveted by The Metals Company, the vast majority of species living there are completely unknown to us, according to research published at the end of May in the journal Current Biology. Using various records, a team of British, Norwegian and Swedish researchers, led by Muriel Rabone, a biologist at London's Natural History Museum, has counted 5,578 benthic (bottom-dwelling) species, most of which were unknown to science. Only 436 of these had already been named, and six had only recently been described: two sea cucumbers, a worm-like organism (Erebussau tenebricosu), a carnivorous sponge, a crinoid (Hyocrinus foelli) and the antipatharian coral.

The mystery of the biodiversity existing at depths of over 4,000 meters, with no light and little food, requires further research. "Baseline biodiversity knowledge of the region is crucial to effective management of environmental impact from potential deep-sea mining activities," the authors argue. They cite another of the rare statistics around deep-sea life, carried out in the Southern Ocean. There, 674 species of isopods (crustaceans) have been recorded, 87% of which are new to science. Such is the lack of knowledge about this deep universe, often referred to as the new frontier, that its geography is less well known than that of the Moon. Barely 25% of underwater landforms have been mapped in high resolution.

The French Research Institute for Exploitation of the Sea (IFREMER) has been observing this extraordinary world since 2010 from a scientific station comprising a range of ecological and geophysical measurement tools. The station is immersed in the Atlantic, at a depth of 1,700 meters, off the Azores. Each year, the Pourquoi Pas? ("Why Not?"), a vessel in the French oceanic fleet, visits the site above a field of hydrothermal vents known as Lucky Strike. Around 70 sailors, scientists, engineers and technicians take part in these month-long missions.

Biologists, ecologists and physicists take turns day and night to follow the images taken by the Victor robot. During its delicate dives, this submersible follows in the footsteps of the modioles – deep-sea mussels – giant shrimps, worms and white crabs that inhabit this cold, dark space. There's no room for laymen on board, except one: Writer David Wahl had the privilege of embarking on the Pourquoi Pas? in 2017. His story first gave rise to theatrical adaptations, then became the subject of a book (La Vie profonde. Une expédition dans les abysses, "Life in the Deep: An expedition into the abyss")

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