Scientists Study Whale Carcass to Understand Ecosystems Thriving in Benthic Depths
Life may come to an end, but life continues to thrive even in the depths of the ocean. Researchers have discovered that the remains of a whale carcass can create and support a mini ecosystem for decades after the whale’s death.
These massive carcasses, known as “whale fall”, offer a bountiful feast for marine life. One such whale fall was discovered by Monterey Bay Aquarium Research Institute researchers in 2009 off the coast of British Columbia at a site called Clayoquot Slope, 1,250 meters (4,100 feet) deep under the waters of the North Pacific.
Since 2012, scientists from Ocean Networks Canada (ONC) have been returning to the site to study the decomposition rate of the whale skeleton and monitor the changes in marine life diversity that flourish on this rich food source. The latest visit to the site was part of an expedition conducted by the Ocean Exploration Trust’s (OET) EV Nautilus to check on underwater observatories operating in Clayoquot Slope.
During the expedition, a remotely operated submersible, known as ROV Hercules, captured high-resolution video and conducted a photogrammetry survey of the whale fall. This survey was led by benthic ecologist Fabio De Leo of ONC.
“Whale falls represent an oasis of food supply in an often food-poor deep-sea floor and sustain a diverse assemblage of marine organisms,” OET wrote in a blog post.
Another whale fall was discovered in 2019 on the Davidson Seamount, which lies at a depth of 3,200 meters. This carcass, only four months old at the time of discovery, was found teeming with octopuses, eelpouts, worms, grenadiers, and crabs.
Although the Clayoquot whale fall is situated in shallower waters, the depths are still bathed in perpetual darkness as the sunlight cannot reach these bathypelagic depths.
The exact species to which the Clayoquot whale fall belonged remains unknown. However, De Leo suggests that it is located near a migration route for gray whales (Eschrichtius robustus), making this identification likely. Remarkably, even 14 years after its discovery, the whale fall site continues to harbor a thriving ecosystem.
“The skeleton supports a rich benthic fauna,” according to OET. Species observed include limpets (Cucculina craigsmith), sea snails (Mitrella (Astyris) permodesta), isopods (Ilyarachna profunda), crabs (Paralomis multispina), rattail fish (Coryphaenoides acrolepis), and tube worms (Lamellibrachia cf. barhami).
Interestingly, many of the sea snails appear to be perched atop tall columns, which are actually their eggs. This not only replenishes the whale fall ecosystem with new baby sea snails but also provides food for other animals, such as crabs, which feast on the eggs.
In addition to the survey, researchers collected sediment samples from the seafloor around the whale fall. These samples will be tested for environmental DNA, which will provide valuable information about the organisms thriving in the darkness, feeding off this corpse-fed ecosystem.
To stay updated on the adventures of the EV Nautilus, interested individuals can follow along on the Ocean Exploration Trust’s Nautilus Live website.