Deep-sea scientists exploring the Indian Ocean came across a vast whale graveyard stretching for around 1,200 kilometres.
The researchers believe this is the deepest and most extensive ‘whale graveyard’ ever discovered – and some of the fossils are around 5.3 million years old.
Xiaotong Peng, a deep-sea researcher from the Chinese Academy of Sciences, and colleagues have published their discovery in Nature.
Scientists first came across whale fossils while exploring the seafloor in a deep-sea submersible at 7,002 metres deep in 2023.
“Following the initial discovery, we conducted 32 dives to the sea floor, aiming at mapping the spatial distribution and extent of the whale falls and fossils, as well as identifying any associated whale-fall ecosystems,” write the authors in the paper. In total, they documented five whale fall communities and 476 fossilised cetaceans.
For whales, there is life after death. When their massive bodies sink to the ocean floor, the smell draws animals from far and wide to join the feast.
“This sudden presence of rich, organic material can feed generations of marine life, leading to a bustling community of fish, scavengers, microorganisms, and more,” writes the Florida Museum on its website. “Think of it as a whale’s final contribution to its underwater home.”
This veritable buffet can sustain deep-sea creatures for many years. First scavengers arrive to eat the whale’s tissue and blubber. Then, other smaller organisms turn up, including bone-eating worms.
The decomposing whale’s body and bones release sulphur and methane, which are broken down by bacteria and ‘chemosynthetic’ animals that create energy from chemical reactions.
“These bacterial and chemosynthetic communities found in deep-sea whale falls actually resemble communities found in hydrothermal vents or cold seeps,” writes the Florida Museum. “This sulphophilic, or sulphur-loving, stage of whale falls can last for decades!”
The five whale carcasses the scientists found were in this sulphophilic stage. “Bones are covered with dense, whitish microbial mats and bone-boring worms Osedax, indicating prolonged residence on the sea floor,” they write in the study. “Active whale-fall ecosystems were found thriving around both baleen and beaked-whale carcasses.”
From what they saw from the submersible, the researchers believe there could be as many as 759.5 individual whale remains per square kilometre in this extensive graveyard.
Many of the remains are from two types of deep-diving whales: strap-toothed beaked whales and Andrews’ beaked whales. These species swim to extraordinarily deep waters to hunt deep-sea fish and squid so probably visited this ocean zone to forage.
“These beaked whales possess extraordinary physiological adaptations for deep diving, routinely reaching depths more than 1,000 m and holding their breath for more than [an] hour,” write the authors. “The maximum dive depth for beaked whales is estimated to be more than 3,000m on the basis of lung collapse and oxygen storage.”
But diving even deeper could be beyond even their capabilities. “Foraging at depths exceeding 3,000m would be too physiologically taxing for beaked whales and may heighten the risk of fatal exhaustion or decompression sickness,” they write. “Natural mortality, combined with the inherent risks of deep diving, probably contributes to the accumulation of beaked whale remains in the sea floor of this zone.”
As the dead whales sink to the seabed, the V-shape of this underwater landscape might funnel their carcasses into a more concentrated area, creating this busy graveyard.
Deep-sea whale falls are difficult to come across and, so, poorly understood. Finding this enormous graveyard gives researchers an opportunity to learn much more about the different species that area supported by whale falls and how they live.
Some of the creatures they found may even be new to science. “The results support the hypothesis that deep-sea whale falls act as evolutionary hotspots,” write the authors.
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Top image: Getty
