Millions of fossil whale bones found in deep-ocean ‘necropolis’

Fossils including possible baleen-whale ribs found at a depth of 5656 metres in the Indian Ocean Global TREnD, IDSSE The world’s deepest known whale graveyard has been discovered in the southern Indian Ocean at a depth of 7 kilometres. The remains found there include a new species of extinct beaked whale and other fossils that are over 5 million years old. In early 2023, Peng Zhou at the Chinese Academy of Sciences and his colleagues undertook 32 dives in a crewed submersible along 1200 kilometres of the seafloor, in an area known as the Diamantina Zone. Orcas have begun wearing salmon hats again – and we may soon know why The expedition was part of the Global Hadal Exploration Programme, an effort led ’s oceans, which range from 6000 to 11,000 metres below the surface. At these depths there is no light, and life must survive on what falls from the surface or generate its own energy from chemicals – known as chemosynthesis. The first fossil whales were found at a depth of 7002 metres in a part of the Diamantina Zone known as the Dordrecht Deep, which is over 1100 kilometres south-west of Perth, Western Australia. “With the sub’s powerful lighting system, we could see tens of metres around us on the otherwise pitch-dark seafloor,” says Zhou. What they saw was “a little scary, but also incredibly fascinating”, he says. The researchers estimated there were up to 760 individual whales per square kilometre, including both ancient and recent carcasses, constituting what they have called a “whale necropolis” and a “deep-sea fossil megasite”. The recently fallen carcasses, which included a 5-metre long Antarctic minke whale (Balaenoptera bonaerensis), provide food to a thriving ecosystem of invertebrates – such as bone-eating worms and brittle stars – many thought to be new species, found in densities of up to 2800 individuals per square metre. “It felt profoundly special,” says Zhou. “We were looking at the final resting place of millions of whales – some over 5 million years old – a deep time archive of evolution and deep-sea life. It was humbling and awe-inspiring, and we treated the site with the respect it deserves.” The manipulator arm of the submersible Fendouzhe collected whale fossil bones on the deep seafloor Global TREnD, IDSSE Altogether, the team found 485 active whale-fall and fossil-whale sites during their expedition. Using the submersible’s robotic arms, they collected 43 fossil specimens that were dated to between 120,000 and 5.26 million years old. Among the younger fossils, most were beaked whales belonging to two living species, Andrews’ beaked whale (Mesoplodon bowdoini) and the strap-toothed whale (Mesoplodon layardii).