In 2009, researchers on the Clayoquot Slope off Vancouver Island spotted a large whale skeleton resting on the seafloor. Most of its soft tissue was already gone. The carcass sat at a depth of 1,288 meters, and a team of scientists recognized a rare chance to track what happened next. For 15 years, they returned to the same bones. What they recorded, according to research published in Frontiers in Marine Science, was a deep-sea habitat that refused to fade.
The whale, likely a blue or fin whale, had already moved through the earliest stages ofdecomposition by the time it was discovered. The new study focuses on what came after. The third stage, called the sulphophilic stage, has now persisted for at least 21 years. The authors expect it may continue for another decade. That finding challenges earlier predictions that this phase runs its course more quickly.
“What was so special,” said Fabio De Leo from the University of Victoria, “is that unlike any previous whale fall studies, we were able to return to the same location and survey the skeleton with a cm-scale precision photogrammetry technique.”
The Bones Barely Changed Across 11 Years
The research team, led by Ocean Networks Canada and the University of Hawaii at Manoa, piloted remotely operated vehicles to the site four times between 2012 and 2024. From the video surveys, they built high-resolution 3D models and measured bone loss with centimeter precision.
The skull and 23 caudal vertebrae held up. Between 2012 and 2023, the vertebrae shortened by an average of just 1.4 percent. The mandibles eroded more, with one fragment losing 7.8 percent of its length. The authors wrote in Frontiers in Marine Science that the cranium and vertebrae will likely “persist for at least another decade.”
While the bones resisted decay, the organisms living on them shifted. In 2009, Osedax worms, commonly called zombie worms, bored into the skeleton. By the last survey, none remained. The researchers hypothesize that the worms ran out of accessible resources or were pushed out by spreading microbial mats. What took their place was a full sulphophilic community: 33 vestimentiferan tube worms (Lamellibrachia cf. barhami), live vesicomyid clams, provannid gastropods, and more than 100 empty clam shells.
Bacterial Mats Grew Thicker Over Time
The sulphophilic stage runs on bacteria that digest lipids locked inside the bones and release sulfur compounds. Other specialists then feed on those compounds. Between 2012 and 2023, bacterial mat coverage expanded measurably. On the vertebrae, it climbed from 39.9 percent to 48.6 percent. On the skull bones, it rose from 27.0 percent to 30.7 percent. The increase was statistically significant, signaling that the sulphophilic stage was still ramping up during the study.
“This means that animals that are whale fall specialists will always find a new home when their larvae drift away, as other whale carcasses will be persisting on the seafloor in the same sulphophilic stage,” De Leo said, via a report in Discover Wildlife.
By 2023, the team counted 31 megafaunal taxa within one meter of the remains. The most numerous resident was the gastropod Neptunea cf. amianta, with 74 individuals. Thirty-six tower-shaped Neptunea egg masses covered the skull bones, a sign the skeleton was doubling as a nursery. Nearly a year later, egg masses still clung to the same spots, though fewer remained and no adult snails sat on top of them.
Expanding Low-Oxygen Zones Worry Researchers
The Clayoquot Slope site sits inside a persistent low-oxygen region known as an Oxygen Minimum Zone. Dissolved oxygen there averages 0.46 milliliters per liter. The study authors note that such zones are expanding and shoaling in the Northeast Pacific as the climate warms, deepening by as much as 3 meters per year in some locations.
If oxygen levels dip below 0.33 milliliters per liter, a threshold documented for Osedax survival at other sites, these bone-eating worms may fail to colonize new whale falls. The researchers warn that losing Osedax would alter the entire bone breakdown process and cut species diversity at whale falls. For now, the Clayoquot site remains above that critical oxygen line, and the absence of Osedax there is not blamed on oxygen stress.
The sulphophilic stage at this whale fall has lasted more than two decades, matching timelines observed off southern California. The lipid-rich skull and vertebrae continue to degrade slowly. Bacterial mats are still spreading. The chemosynthetic fauna remain. The study, published in Frontiers in Marine Science, suggests this deep-sea community will keep feeding on the bones for years to come.
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