The plan seemed simple: a team of researchers led by Ocean Networks Canada would conduct an experiment to lure a species of deep-sea worms to colonize whale remains placed on the seafloor.
However, after more than 10 years of observation, the researchers report finding no sign of the odd deep-sea organisms they had hoped to attract.
Beginning in 2009, the team placed humpback whale bones in Barkley Canyon, nearly a thousand meters deep, and monitored them using high-resolution cameras and sensors. After more than a decade, the bones showed little sign of activity, despite the worms’ important role in recycling nutrients in the deep sea, according to findings now published in a study that appeared in Frontiers in Marine Science.
The Role of Zombie Worms in Whale Falls
Osedax are deep-sea worms often called zombie worms because they feed on decaying whale bones. They lack mouths or digestive tracts, so they use root-like structures to burrow into bones. Microbes living in these roots help the worms get nutrients from the bones.
By breaking down whale bones, these zombie worms help release nutrients, allowing other species to colonize the remains. In most whale falls, this process supports a diverse community for years or even decades, transforming a whale carcass into a temporary habitat on the seafloor.
However, during the experiment at Barkley Canyon, this colonization sequence did not occur.
A Meaningful Absence
Despite more than ten years of continuous monitoring, researchers found no evidence that Osedax ever colonized the bones placed on the seafloor. In experimental science, scientists classify this kind of outcome as a negative result. In this case, it can be just as informative as a positive one.
“This was a remarkable observation in such a long-term experiment,” said Fabio De Leo, a senior staff scientist with Ocean Networks Canada and co-lead author of the study. De Leo and his colleagues suggest the worms’ absence may be linked to unusually low oxygen levels at the site.
Barkley Canyon sits in a naturally low-oxygen area along the northeast Pacific. Scientists refer to these areas as oxygen minimum zones, or OMZs, which form when ocean currents and marine life consume available oxygen. Many OMZs have grown larger over recent years, linked to ocean warming.
When Whale Falls Stop Working
If Osedax worms aren’t present, this process might not work as it should. The study points out that low oxygen levels could disrupt the early stages of whale-fall succession, making it harder for nutrients from bones to move into the rest of the ecosystem.
Signals From the Deep Sea
The team observed similar trends with another ecosystem engineer. Wood-boring Xylophaga bivalves colonized submerged wood at Barkley Canyon, but at much lower rates than in areas with higher oxygen levels. Slower colonization could delay carbon breakdown and reduce habitats for species that depend on these burrows. These results indicate that declining oxygen levels may be influencing multiple deep-sea recycling processes simultaneously.
“It looks like the OMZ expansion, which is a consequence of ocean warming, will be bad news for these amazing whale-fall and wood-fall ecosystems along the northeast Pacific margin,” said Craig Smith, a professor emeritus at the University of Hawaii and co-lead author on the study.
Watching the Seafloor in Real Time
The research used Ocean Networks Canada’s NEPTUNE observatory, a network of cabled instruments that supply continuous power and data from the deep seafloor. Cameras at the Barkley Canyon Mid-East site recorded high-definition video over many years, providing a detailed look at slow ecological changes that shorter studies often miss.
Deep-sea researchers worry about more than just one species. More whale-fall experiments are happening at other NEPTUNE sites, like Clayoquot Slope. Early findings look similar, but the researchers say they need more data before reaching conclusions.
Austin Burgess is a writer and researcher with a background in sales, marketing, and data analytics. He holds a Master of Business Administration, a Bachelor of Science in Business Administration, and a Data Analytics certification. His work combines analytical training with a focus on emerging science, aerospace, and astronomical research.