Vast whale graveyard discovered in Indian Ocean

Chinese-led researchers have discovered the largest known whale graveyard on Earth, a 1,200-kilometer stretch of bones and carcasses deep in the south-eastern Indian Ocean that includes fossils dating back 5.3 million years.

The site lies as deep as 7 kilometers in the Diamantina Zone, also described as the Diamantina fracture zone, west of Australia. Researchers found nearly 500 whale-fossil sites and active whale falls during 32 dives in 2023 by the Chinese submersible Fendouzhe, which carried up to three people and used robotic arms to collect fossil samples.

The findings, published Wednesday in the journal Nature, describe the deepest and oldest known whale graveyard and a thriving deep-sea habitat supported by the remains of whales. Many of the organisms observed there may be new to science, the journal reported.

“Discovering a necropolis of this scale was completely unexpected,” said Xiaotong Peng of the Chinese Academy of Sciences, the study’s lead author. “The size of distribution, the depth and the age range were far beyond anything we had imagined.”

When whales die, their bodies can sink to the seafloor, creating “whale falls” that provide food and habitat for deep-sea animals. At the Diamantina site, researchers saw jellyfish, brittle stars, bone-boring worms, bivalves and crustaceans living among the bones and carcasses. Study co-author Peng Zhou said witnessing the graveyard “was a truly incredible experience.”

“The vibrant ecosystems we saw offered a completely different perspective on this otherwise dark and cold ocean floor,” Zhou said.

Most of the 485 fossils catalogued by the scientists were from different species of beaked whales. The BBC reported that the remains included a five-meter-long Antarctic minke whale carcass, the largest discovery made at the site, and a fossilized skull identified as the 5.3-million-year-old beaked whale Pterocetus benguelae. Researchers also identified a new extinct whale species, which the BBC reported the team named Pterocetus diamantinae after the site.

Scientists believe whales may have died in large numbers in the area because it is a popular foraging habitat and because a V-shaped trench helps funnel carcasses to the seafloor. Based on the number of bones found, the research team estimated that more than 10 million carcasses could be spread across the area.

Xiaotong Peng said the soft tissue and lipids in that many carcasses would amount to roughly 6.7 million tonnes of sequestered carbon. The study said the carcasses provide a major source of sustenance in the deep ocean, in a way comparable to hydrothermal vents that support their own ecosystems.

Some animals observed at the site also live around hydrothermal vents and cold seeps, suggesting whale falls may help connect deep-sea communities. The study’s authors wrote that the results support the idea that deep-sea whale falls act as “evolutionary hotspots and biogeographic stepping stones for sulfide-dependent fauna in the deep ocean.”

Xikun Song, a biologist at the Chinese Academy of Sciences’ Institute of Deep-sea Science and Engineering who was involved in the find, told The Associated Press that a whale’s size and the chemistry of its bones help create these underwater communities. “At the same time, the very nature of the deep ocean makes these sites exceptionally difficult for scientists to locate,” Song wrote in an email.

Outside researchers called the discovery significant. University of Hawaii oceanographer Craig Smith, who discovered the first whale fall in 1987 and was not involved in the new work, told AFP it was “extremely exciting.” Stephen J. Godfrey of the Calvert Marine Museum wrote in Nature that the find was “a truly unique discovery” and could inspire more submersible dives in similar environments. “I hope that there will be many more of these blockbusters to come,” he wrote.