Scientists Discover 5.3-Million-Year-Old Whale Necropolis in Diamantina Zone of Southeastern Indian Ocean

Scientists have discovered a vast whale necropolis in the Diamantina Zone of the southeastern Indian Ocean, extending about 1,200 km along the sea floor and reaching depths of 4,616 to 7,001 m.

“extending about 1,200 km along the sea floor of the southeastern Indian Ocean”

Nature

The Nature study says the area comprises five modern natural whale-fall communities and 476 fossil cetaceans, with isotopic dating showing whale falls in the region have occurred since at least 5.3 million years ago.

Australian Broadcasting Corporation

During 32 dives from 8 February to 17 March 2023 using the Fendouzhe submersible, researchers identified 476 whale fossils and five carcasses of whales that had died more recently at depths between 13,800 and 23,000 feet.

Live Science reports the team used the underwater vehicle to survey the seafloor after initially spotting one fossil, then conducted 32 dives covering a survey area of about 0.25 square miles.

In the same Nature account, the Diamantina Zone is described as lying to the south of the Broken Ridge and Perth Abyssal Plain, stretching about 1,200 km parallel to the Southeast Indian Ridge.

The study describes carcasses hosting specialized communities dominated by brittle stars, bone-boring worms and chemosynthesis-based bivalves, while the fossil record includes both extant and extinct deep-diving beaked whales.

Live Science quotes Nick Pyenson, a curator of fossil marine mammals at the Smithsonian National Museum of Natural History in Washington, D.C., saying, "It covers over 1,200 kilometers [750 miles], which just defies belief,".

BBC

The Nature paper says the researchers found that only one specimen could be confidently assigned to a species, a clam known as Abyssogena southwardae, and it notes that many other members of the whale-fall communities may be newly discovered species.

Live Science adds that the five active whale falls are covered in bacteria that live without light or oxygen and break down the oils in the whales' bones, producing hydrogen sulfide.

Stephen Godfrey, curator of paleontology at the Calvert Marine Museum in Maryland, told Live Science, "The density is crazy" as he described each whale fall as a new "little restaurant" for deep-sea life.

The Nature study says the findings reshape understanding of the limits and biogeography of whale-fall ecosystems and establish some deep sea floors as a fossil archive for tracing cetacean evolution over geological time.

“"may be new to science"”

BBC

BBC reports that during 32 dives explorers collected samples from 485 whale-fossil sites and active whale falls, and it highlights a beaked Pterocetus benguelae skull dated to 5.3 million years ago and a new species called Pterocetus diamantinae.

In a separate account, the Guardian says the newly discovered necropolis reaches depths of more than 7km and extends hundreds of miles across the sea floor, while researchers found decaying carcasses teeming with life.

BBC quotes Nature’s description that the site is "teeming with organisms and species that "may be new to science"" and it frames the discovery as prompting huge excitement because of the age of the remains.

The Guardian adds that the team noted the falls are "Aligned along a northwest-southeast axis for 1,200km" and suggests they may form a previously unrecognised "whale-fall community supercorridor."