Even when dead, whales continue to be present on the ocean floor, sometimes for decades. A real ecosystem is then created around their corpse, rich and complex, as revealed by a study published by Frontiers in Marine Science and relayed by IFL Science. The carcasses of the largest animals in the world then become a true sanctuary of underwater species, varying over time.
In its report, the research company Ocean Networks Canada reveals having discovered a whale carcass at the bottom of the ocean in 2009 and having regularly observed it since then using remote-controlled cameras, in 2012, 2020, 2023 and 2024. An unprecedented long-term study, which made it possible to see the importance of cetaceans even after their death.
Over the last fifteen years, scientists have seen the appearance of dozens of species which have taken turns throughout the different stages of decomposition. First, sharks, crabs and other scavengers devour the flesh of the whale, then comes the turn of worms and crustaceans which feed on the organic matter of the bones and have infused the surrounding sediments.
Finally comes the time of the sulfophilic phase, devoted to sulfur-loving species: tube worms, clams, sea snails then form symbiotic relationships with sulfur-oxidizing bacteria which, together, break down the lipids trapped inside the bones, thus releasing sulfur-based chemical compounds that other species consume. The final stage of this feast takes place at the skeleton level: the coral begins to live on the bones which become a permanent structure of the seabed.
Global warming
One of the major phases of decomposition is that linked to the presence of sulfur-oxidizing bacteria, which work for many years on the corpse. Between 2012 and 2023, the researchers observed that these bacteria very gradually occupied a larger part of the surface of the skeleton.
In 2024, researchers estimate that the sulfurization stage has already been underway for more than twenty-one years, and that it could last another decade. However, the decomposition process in whales is usually faster. How can we explain that it takes so long in this specific case?
We must undoubtedly look for the answer in the location of the site: on the edge of a minimum oxygen zone (ZOM), whose lack of oxygen deters certain species from participating in the feast, which slows down the entire process.
These ZOMs are extending more and more into the oceans, in particular because of climate change. For researchers, this means that we will undoubtedly observe many more whale carcasses, degrading very slowly at the bottom of the water.
Good news for scientists, but which could have serious and still unknown consequences for the seabed: “We hypothesize that the functioning of the whale carcass ecosystem and associated biodiversity could be threatened by the widespread expansion of hypoxic environments”concludes the article.
