main article image
(EV Nautilus/YouTube)

Biologists Get Morbidly Excited Over Discovering a Rare 'Whale Fall'

MICHELLE STARR
18 OCT 2019

The sea wastes nothing.

When a dead whale makes its final fall to the floor of the ocean, far from the rippling light of the Sun, its mighty carcass becomes a feast for the dwellers in the dark.

 

Such a bounty from above creates a new ecosystem where life can thrive for decades at depths below 1,000 metres (3,280 feet) from the surface - deep in the bathypelagic zone where the water pressure becomes crushing, and light never penetrates.

Since the ocean floor is so inhospitable to humans, the sight of a whale fall, for us, is a rare one.

Imagine the excitement, then, of a team of marine researchers from the Monterey Bay National Marine Sanctuary aboard the EV Nautilus when they found one during a livestream from one of the vessel's remotely operated underwater vehicles.

Actually, you don't have to imagine it. They'll tell you.

In a video posted to YouTube, you can hear them gush over the find - "We are so excited up here!" one researcher exclaims.

The carcass was found while exploring the Davidson Seamount off the coast of California, at a depth of 3,200 metres (10,500 feet).

Even in the cold, dark, high-pressure, low-oxygen environment that far from the surface, life has found a way.

Generally, food is relatively scarce, but the rich abundance supplied by the carcass of Earth's biggest creatures draws swarms of creatures to gorge.

 

The fall, the team ascertained, is a relatively recent one, around 4 months old, with blubber and some internal organs still remaining.

The species is unclear - the researchers think it's likely a grey whale or minke whale - but it measures 4-5 metres, and is definitely a baleen species, because baleen is clearly visible on its jawbones.

It's in a supine position, with an interestingly diverse array of creatures feeding on its flesh and bones.

"Large scavengers like eelpouts are still stripping the skeleton of blubber, and bone-eating Osedax worms are starting to consume lipids (fats) from the bones," the team wrote in a YouTube description.

"Other organisms seen onsite include crabs, grenadier[s], polychaetes, and deep-sea octopus."

The vehicle lingered over the carcass in the hopes that the whale can be identified; the species might offer some clues as to how it died. If it's a grey whale, for instance, its death might be linked to the unusually high grey whale mortality that's been seen along the west coast of the North American continent this year.

 

But, on the seafloor, the cycle of life continues.

It won't take long for the flesh to be stripped from the bones, and the bones to be stripped of their nutrients. The consumption of the soft tissue by scavengers - called the Mobile Scavenger Stage - usually takes less than a year, and some of the animals that come to partake have never been seen anywhere else.

Organic detritus will seep into the seafloor sediments, providing food for burrowing creatures such as clams and worms. That's the Enrichment Opportunist Stage, and it can last up to two years.

The third and final stage is called the Sulfophilic Stage, when bacterial mats colonise the bare bones of the skeleton, breaking down the lipids in the bones beyond the reach of the Osedax worms, and producing sulfur.

This attracts microbes that consume the sulfur, and molluscs and crustaceans that eat the bacterial mats. A minke whale fall discovered in 2013 ended up hosting several species entirely new to science.

The best part is, the remarkable ecosystem created by a whale fall can persist for decades.