Scientists are alarmed by the absence of zombie worms on whale bones placed in the deep ocean off British Columbia. After 10 years of monitoring, none of these key ecosystem engineers appeared, likely due to low oxygen levels. The finding raises concerns about climate-driven disruptions to deep-sea habitats.
In a long-term experiment off the coast of British Columbia, researchers lowered humpback whale bones to the seafloor in Barkley Canyon, about 1,000 meters below the Pacific Ocean surface. The site, part of Ocean Networks Canada's NEPTUNE observatory, lies within a naturally low-oxygen zone along migration routes for humpback and grey whales. Led by Fabio De Leo of Ocean Networks Canada and the University of Victoria, along with Craig Smith of the University of Hawaii, the study aimed to observe how whale falls—sunken whale carcasses—support deep-sea life.
Zombie worms, scientifically known as Osedax or "bone devourers," typically colonize these bones quickly. These unusual creatures lack a mouth, anus, or digestive tract, instead using root-like structures to host microbes that extract nutrients from the bone. As ecosystem engineers, they break down remains, recycle nutrients, and pave the way for other species, creating rich biodiversity hotspots akin to underwater islands.
However, high-resolution underwater footage over 10 years revealed no trace of the worms. "This was a remarkable observation in such a long-term experiment," De Leo noted, attributing the absence to unusually low oxygen levels in expanding oxygen minimum zones (OMZs), a consequence of ocean warming. Without Osedax, the ecological succession process stalls, potentially limiting nutrient access for other organisms and leading to species loss. De Leo warned, "Basically, we're talking about potential species loss," as larvae rely on ocean currents to connect distant whale fall sites.
The experiment also showed reduced colonization by wood-boring Xylophaga bivalves on submerged wood, delaying carbon decomposition and habitat formation. "It looks like the OMZ expansion... will be bad news for these amazing whale-fall and wood-fall ecosystems along the northeast Pacific Margin," Smith said. Data came from video cameras, sensors, and remotely operated vehicles, with further findings expected from ongoing monitoring at the Clayoquot Slope site. The research, supported by the Canada Foundation for Innovation and the US National Science Foundation, underscores threats to UN Sustainable Development Goal 14 on life below water.