A find which reveals a little-known ecosystem more than 5 million years old.
Nearly 7,000 meters below the surface of the Indian Ocean, researchers made an unexpected discovery: an immense necropolis of whales. They carried out 32 dives on the seabed to map the distribution and extent of carcasses and fossils, and to identify associated ecosystems. They identified 485 cetacean skeletons or fossils spread over nearly 1,200 kilometers of depth. “Dating indicates that whale carcasses formed in this region at least 5.3 million years ago” they share in the journal Nature. Never before has such a collection of whale remains been observed at such a depth.
Far from being simple abandoned bones, these carcasses are true “oasis of biodiversity on the seabed”. When a whale dies and sinks to the bottom of the ocean, its body nourishes for decades a whole procession of animals capable of surviving in an environment where food is extremely scarce. Scientists have observed serpentine sea stars, worms that burrow directly into bones. Around them gravitated shells, marine snails and bacteria capable of producing their energy without light, making each skeleton an ecosystem in its own right. Some species could even be completely unknown to science. This discovery pushes back the maximum depth known for this type of ecosystem by more than 2,500 meters.
One question remains: why so many whales in the same place? Researchers offer several explanations. According to them, this part of the Indian Ocean constitutes an important feeding area for beaked whales, cetaceans capable of diving more than 1,000 meters in search of squid. Some died during these dives. The V-shape of the submarine fault could then channel the carcasses towards its bottom, while the very low deposition of sediments would slow down their burial. Over millions of years, these conditions would have favored the accumulation and remarkable preservation of bones.
For researchers, this necropolis is a formidable time machine. It contains fossils of extinct species, but also of beaked whales still present today. As these cetaceans live very far from the coast and are rarely observed, their bones could make it possible to reconstruct their history, their evolution and the evolution of their populations over more than 5 million years. A wealth of information on animals that are among the most mysterious on the planet.
