A whale graveyard of unprecedented scale has been found in the deep sea 7,000 meters down in the Indian Ocean. It was also confirmed to be the deepest and widest whale graveyard discovered to date. Not only carcasses of recently dead whales but also fossils of whales that went extinct 5 million years ago were found. It is, in human terms, the confirmation of an enormous communal cemetery spanning from Australopithecus to modern humans.
Researchers at the Institute of Deep-sea Science and Engineering (IDSSE) of the Chinese Academy of Sciences said in Nature on the 10th (local time) that they "found five sites with carcasses of modern whales and 476 sites with fossils of extinct whales at depths of 4,616 to 7,001 meters in the Diamantina Fracture Zone." Teams from the University of Pisa in Italy and GNS Science in New Zealand also took part in the study.
Scientists said the aggregation of whale carcasses will greatly help understand the evolution and distribution of deep-sea ecosystems, not only by sequestering carbon dioxide that causes long-term warming in the deep sea but also by providing nutrients to other organisms. A treasure trove of ocean science that reveals both the past and present of deep-sea ecosystems has been discovered.
◇An enormous communal cemetery stretching 1,200 kilometers
The international research team sailed to the Indian Ocean in 2023 aboard China's Tansuo Yihao ocean research vessel and conducted 32 surveys across the trench and ridge region of the Diamantina Fracture Zone. A ridge is a submarine mountain range, and a trench is a valley deeper than 6,000 meters. This area formed 60 million to 50 million years ago as the Australian continent and the Antarctic continent drifted apart. The whale graveyard was located using the crewed submersible Fendouzhe. This three-person submersible, independently developed by China, can dive beyond 10,000 meters.
News sometimes reports whale carcasses washing ashore, but whales sink to the seabed when they die. This is the "whale falls" phenomenon. Bone graveyards created by whale falls are not uncommon, but most have been found at depths of less than 4 kilometers. The graveyards in this study reach depths beyond 7 kilometers and stretch 1,200 kilometers across the seafloor. They are the deepest and widest whale graveyards.
The team said the density this time reached up to 759.5 whales per square kilometer. Across the entire Diamantina region, more than 10 million whale carcasses are estimated to exist. This means the whale graveyard is an enormous carbon sink. Assuming an average body weight of 2 tons for the predominantly found beaked whales and a lipid content of 25%, about 6.7 million tons of carbon would be sequestered in the deep sea, the researchers explained.
Marine carbon sequestration is mainly achieved as fragments of marine life living near the ocean surface slowly fall into the deep. Because the falling particles resemble snowfall, it is called "marine snow." The team said the whale graveyard they found represents a carbon input comparable to about 4,700 years' worth of marine snow.
◇Fossils of whales extinct 5 million years ago also found
The largest whale carcass the team found was the skeleton of an Antarctic minke whale measuring 5 meters long. It was discovered at a depth of 5,610 meters. Three beaked whale vertebrae were found at 6,789 meters. This set the record for the greatest depth at which carcasses of modern whales have been discovered.
The whale carcasses were sustaining deep-sea ecosystems. The team identified three species of basket stars found only on whale bones. Xyloplax, an echinoderm known to live on sunken wood in the deep sea, was discovered in the whale graveyard. In effect, whale bones served the role of wood.
Until now, deep-sea organisms have mainly been found around hydrothermal vents, the hot springs of the deep sea. At the whale graveyard, annelids such as tube worms and Osedax found at hydrothermal vents, as well as crustaceans and mollusks, were recorded. Osedax is a polychaete that feeds on the bones of marine animals and is called a zombie worm or bone-eating worm.
The researchers said the findings support the hypothesis that whale carcasses can serve as sources for deep-sea biological communities like hydrothermal vents do. Jon Copley of the University of Southampton said, "Species that thrive at hydrothermal vents feed on whale carcasses," 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, which 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? Stephen Godfrey of the Calvert Marine Museum explained two reasons in a commentary published in Nature that day for why the whale bones did not completely decompose. One is that whale bones are inherently very dense and do not easily break down. In addition, mineral coating also played a role. Godfrey said iron-manganese oxides in seawater adhered to the bones and prevented dissolution.
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