The largest whale graveyard on record has been found in the deep sea at a depth of 7,000 meters in the Indian Ocean. It was also confirmed to be the deepest and widest among whale graveyards found so far. Not only carcasses of whales that died recently but also fossils of whales from 5 million years ago that went extinct were found. In human terms, it is as if an enormous communal cemetery has been identified that spans from Australopithecus to modern humans.
Researchers at the Institute of Deep-sea Science and Engineering (IDSSE) of the Chinese Academy of Sciences said in the journal Nature on the 10th (local time) that they found five sites with carcasses of modern whales and 476 sites with fossils of extinct whales in the Diamantina fracture zone at depths of 4,616 to 7,001 meters. Teams from the University of Pisa in Italy and GNS Science in New Zealand also took part in the study.
The scientific community said whale carcass clusters are expected to greatly help understand the evolution and distribution of deep-sea ecosystems, not only because they sequester carbon dioxide that causes long-term warming in the deep sea, but also because they provide nutrients to other organisms. A treasure trove of ocean science that will reveal both the past and present of deep-sea ecosystems has been discovered.
◇An enormous communal cemetery spanning 1,200 kilometers
The international research team sailed to the Indian Ocean in 2023 aboard the Chinese oceanographic vessel Tansuo Yihao and conducted 32 surveys around the trench and ridge areas of the Diamantina fracture zone. A ridge is an undersea mountain range, and a trench is a valley deeper than 6,000 meters. This area was formed 60 million to 50 million years ago as the Australian continent and Antarctica drifted apart. The whale graveyard was found by the crewed submersible Fenduzhe. Developed independently by China, this three-person submersible can dive beyond 10,000 meters.
News about whale carcasses washing ashore appears from time to time, but whales sink to the seafloor when they die. This is the whale fall phenomenon. Bone graveyards formed by whale falls are not uncommon, but most have been found at depths of less than 4 kilometers. These graveyards reached depths of more than 7 kilometers and stretched 1,200 kilometers across the seafloor. It is the deepest and widest whale graveyard.
The team said whale numbers reached as many as 759.5 per square kilometer. Across the entire Diamantina fracture zone, more than 10 million whale carcasses are estimated to exist. This means the whale graveyard is an enormous carbon sink. Assuming the average body weight of the mainly found beaked whales is 2 tons and the lipid content is 25%, about 6.7 million tons of carbon would be sequestered in the deep sea, the team said.
Marine carbon sequestration mainly occurs as fragments of marine organisms living near the ocean surface slowly fall into the deep sea. Because this falling powder looks like snow, it is called marine snow. The team said the whale graveyard they found equals the amount of carbon input that would accumulate over about 4,700 years of marine snow.
◇Fossils of whales from 5 million years ago found as well
The largest whale carcass the team found was the skeleton of an Antarctic minke whale measuring 5 meters in length. It was found at a depth of 5,610 meters. Three beaked whale vertebrae were discovered at 6,789 meters. It set the record for the greatest depth at which modern whale carcasses have been found.
The whale carcasses were sustaining the deep-sea ecosystem. The team identified three species of basket stars found only on whale bones. Xyloplax, an echinoderm known to live on wood that has sunk to the deep sea, was found in the whale graveyard. Whale bones, in effect, played the role of wood.
Until now, deep-sea creatures have mainly been found around hydrothermal vents, which are the hot springs of the deep sea. At the whale graveyard, annelids such as tubeworms and Osedax that live at hydrothermal vents, as well as crustaceans and mollusks, were found. Osedax is a bristle worm that feeds on the bones of marine animals and is known as a zombie worm or bone-eating worm.
The team said the findings support the hypothesis that whale carcasses can serve as a source of deep-sea biological communities like hydrothermal vents do. Jon Copley of the University of Southampton said, "Species that thrive at hydrothermal vents use whale carcasses as food," adding, "Whale carcasses serve as island-like habitats for deep-sea organisms."
In particular, the team also found the skull of an extinct beaked whale called Pterocetus benguelae, estimated to be 5.3 million years old. They also identified a new extinct beaked whale species they named Pterocetus diamantinae. Radiometric dating showed the fossils were at least 5.3 million years old. In human terms, this was when Australopithecus was active.
How could a beaked whale skull fossil have been preserved despite being exposed to seawater for more than 5 million years? In a commentary published in Nature, Stephen Godfrey of the Calvert Marine Museum explained two reasons why the whale bones did not completely decompose. One is that whale bones are originally very dense and resist decomposition. In addition, mineral coating played a role. Godfrey said iron-manganese oxides in seawater adhered to the bones and prevented them from dissolving.
References
Nature (2026), DOI: https://doi.org/10.1038/s41586-026-10546-z
Nature (2026), DOI: https://doi.org/10.1038/d41586-026-01581-x