Deepest known whale graveyard found in Indian Ocean has been active for over five million years

Chinese deep-sea researchers have discovered what is believed to be Earth's deepest and most extensive known accumulation of whale fossils and carcasses, in the Diamantina Fracture Zone of the southeastern Indian Ocean. The study, published in the journal Nature, was led by scientists from the Chinese Academy of Sciences with researchers from the University of Pisa and Earth Sciences New Zealand.

When a dead whale sinks to the ocean floor, its carcass creates a localised ecosystem, known as a whale fall, that feeds a variety of deep-sea organisms. Most previously documented whale falls lay at depths of less than 4,000 metres, with the deepest on record at 4,204 metres. The newly discovered site spans roughly 1,200 kilometres of seafloor at depths of 4,200 to 7,002 metres, and includes an active whale-fall ecosystem at 6,789 metres, the deepest known example of its kind.

Researchers aboard the Chinese submersible Fendouzhe first identified whale falls and fossils in the area between February and March 2023, then conducted 32 more dives to map the remains. They documented 485 whale-fossil sites, including five active whale falls, and estimated that more than 10 million whale carcasses could exist across the broader area. Isotopic dating suggests the oldest fossils are about 5.3 million years old. Many belonged to deep-diving beaked whales, and the team formally named a previously unknown extinct species, Pterocetus diamantinae.

The scientists recorded 35 groups of larger organisms living on the remains, dominated by worms, crustaceans and molluscs, along with brittle stars and bone-eating worms; some may be new to science. The authors propose that natural mortality and the physical strain of deep diving — beaked whales regularly dive beyond 1,000 metres — may explain the accumulation, with the fracture zone's V-shaped topography funnelling sinking carcasses into one area. The largest whale fall documented was a five-metre Antarctic minke whale at 5,610 metres, identified through genetic analysis and its ear bones.