Zombie worms, the mysterious bone-devouring creatures of the deep ocean, have gone missing, and scientists are concerned. These worms, known as Osedax, play a crucial role in breaking down whale bones and supporting the delicate balance of deep-sea ecosystems. But their disappearance may signal a much larger ecological issue, one that could lead to species loss and weakened ecosystems linked to long-term climate change.
A decade-long experiment off the coast of British Columbia, led by Ocean Networks Canada (ONC) and the University of Victoria, placed humpback whale bones on the ocean floor and monitored them for signs of life. After years of observation, researchers found no trace of zombie worms, despite their well-known role in breaking down whale bones and supporting deep-sea food webs.
Osedax worms are unique in that they lack a mouth, anus, and digestive tract, yet they survive by drilling root-like structures into bone. Inside those roots live microbes that extract nutrients, which then nourish the worms. This unique role makes Osedax an ecosystem engineer, helping to recycle nutrients and create conditions that allow other species to move in.
The absence of zombie worms is concerning because it may be linked to unusually low oxygen levels at the study site. Over 10 years of high-resolution underwater camera footage from ONC failed to capture any zombie worm colonization. This kind of outcome is known as a negative result, and it can be just as meaningful as a positive finding.
The whale bones were placed in Barkley Canyon, nearly a thousand meters below the Pacific Ocean surface. This area lies within a naturally low-oxygen zone and along migration routes used by humpback and grey whales. When whales die, their bodies sink to the seafloor, creating 'whale falls' that normally provide a sudden surge of food that supports rich biodiversity. The lack of zombie worms at Barkley Canyon suggests that expanding oxygen minimum zones (OMZs) in the northeast Pacific and beyond may be disrupting these ecosystems.
The research team also found signs that another ecosystem engineer may be under stress. Wood-boring Xylophaga bivalves were present on submerged wood samples at Barkley Canyon, but their colonization rates were far lower than in oxygen-rich waters. Slower colonization could delay carbon decomposition and reduce habitat formation for the many species that typically live inside Xylophaga burrows.
The disappearance of zombie worms could lead to species loss. Adult Osedax typically live on whale bones, while their larvae travel long distances through ocean currents to colonize new whale falls, sometimes hundreds of kilometers away. If those habitats disappear or stop functioning properly, connectivity between whale fall sites breaks down. Over time, this could lead to declining diversity of Osedax species across entire regions.
The research was supported by the Canada Foundation for Innovation Major Science Initiative Fund and partly by a US National Science Foundation grant. It also aligns with United Nations Sustainable Development Goal 14, life below water.
