The zombie worm is disappearing. And no, that’s not good news, it points to another potential imbalance in the ecosystem. an experiment that lasted 10 years, led by Ocean Networks Canada (ONC) and from University of Victoria (Canada), not found in the ocean floor of British Columbia clues to the presence of the animal, which plays a fundamental role in the decomposition of bones.
In research on the ocean depths, also the absence of a creature in particular, the so-called zombie worm, the “bone eater” (Osedax), can be worrisome, a harbinger of species loss and ecosystem decline due to the long-term effects of climate change.
What are zombie worms and why do we need them
Osedax is a genus of polychaete family annelids Siboglinidae which, despite having no mouth, anus or digestive system, has roots that penetrate bones and microbes that extract nutrients to feed the worms.
And the fact that ONC’s high-resolution underwater cameras did not detect zombie worm colonization on bones in 10 years of observation is a very concerning finding.
In fact, if the “bone eater” is not present to carry out its tasks, other species may not be able to colonize and further utilize the nutrients of the whale carcasses, a habitat reference point for this and many other species specializing in whale bone excavations.
In fact, whales that die from natural causes or human threats, such as collisions with ships or fishing nets, often sink to the seabed, creating a mine of food to support new hotspot of biodiversity.
“Basically, we are talking about a potential loss of species – explains Fabio De Leo, who led the study – Osedax adults generally grow on whale bones and their larvae disperse large distances in the ocean to populate other whale cascade ecosystems even hundreds of kilometers away. So, this connectivity, these island habitats, will no longer be connected, and we could start to lose a diversity of Osedax species on regional spatial scales.”
What did researchers observe and what are the causes
Researchers conducted an experiment that studied humpback whale bones deposited on the ocean floor off the coast of British Columbia (BC), and after 10 years of observations, they found no evidence of the presence of the zombie worm.
“This was a remarkable observation in such a long-term experiment, which could be explained by the low oxygen concentrations present at the observation site.”
The Barkley Canyonwhere whale bones were placed nearly a thousand meters below the surface of the Pacific Ocean, is located in a naturally oxygen-poor area, located along the migratory routes of humpback and gray whales.
But the absence of zombie worms on these bones suggests that the expansion in the northeast Pacific of oxygen minimum zones (OMZs), where oxygen saturation in the water is at its lowest, could alter these ecosystems more broadly. And among the main causes, unfortunately, are climate change.
A situation that could be even more serious
And alas, this situation could also be verified elsewhere: preliminary data from ongoing research on whale falls near another ONC site, in fact, suggests that zombie worms could be affected not only where this long observation was carried out.
Additionally, the researchers found that another ecosystem engineer, the species of Xylophagabivalviwhich perforate wood, appears to be affected by oxygen deficiency stress. Although these bivalves were observed in the submerged wood samples of experiment a Barkley Canyon, are colonized at much lower rates than more oxygenated ocean areas, with implications for a slowdown in carbon decomposition and colonization by the numerous species that typically populate the burrows of Xylophaga.
The expansion of the OMZ as a result of ocean warming is very bad news for these extraordinary ecosystems along the northeastern edge of the Pacific
he concludes Craig Smithwho co-directed the experiment.
The research was funded by Canada Foundation for Innovation Major Science Initiative Fund and in part by a grant from US National Science Foundation.
Sources: University of Victoria / Ocean Networks Canada/Youtube
