Skip to main content

Tanner crabs dine on bacteria that derive energy from digesting methane.

University of Victoria - Ocean Networks Canada/University of Victoria - Ocean Networks Canada

In the deep ocean some 50 kilometres off the coast of Vancouver Island, a group of Tanner crabs is foraging for food.

Suddenly, one of the crabs rises from the sea floor as if it is hoisted by an invisible force. A moment later, the crab flips over, releasing a large bubble of methane gas from beneath its carapace. It plunges back down, does a faceplant in the silt, then returns to its business – muddied, but seemingly unperturbed.

The curious scene was captured on video at a deep-sea station operated by Ocean Networks Canada, a federally-funded organization that supports marine science. Equal parts Jacques Cousteau and Charlie Chaplin, the video was the clue that led to a newly discovered link between the methane that is seeping out from under North America’s submerged western rim and some of the seafood that finds its way onto restaurant menus.

Story continues below advertisement

The curious scene was captured on video at a deep-sea station operated by Ocean Networks Canada, a federally-funded organization that supports marine science. A team of Canadian and U.S. scientists investigated what attracts the crabs – a migratory species – to this fizzy stretch of the ocean floor. After years of study, the scientists say the crabs are not there by chance, but to dine on bacteria that derive energy from digesting methane. Ocean Networks Canada

The link was uncovered when a team of Canadian and U.S. scientists investigated what attracts the crabs – a migratory species – to this fizzy stretch of the ocean floor. After years of study, the scientists say the crabs are not there by chance, but to dine on bacteria that derive energy from digesting methane.

The finding means that the crabs are acting as conduits for channelling food energy from a fossil fuel source into the rest of the marine ecosystem. What makes this especially interesting is that Tanner crabs are marketed and consumed in the United States as “snow crab.” (In Canada, the same term refers to another, related species.) Like the crabs, the people who eat them are also getting a fraction of their caloric intake from the methane bubbling up from the briny deep.

“Humans are benefiting from this directly,” said Fabio De Leo, biological oceanographer at the University of Victoria who was involved in the discovery. In a study published last week in the research journal Frontiers in Marine Science, Dr. De Leo and his colleagues note this is the first time that a commercially harvested species has been shown to derive some of its nutritional value from chemical energy instead of exclusively through the larger ocean food chain that is based on phytoplankton – floating microorganisms that live off of sunlight and play the same role as plants in terrestrial ecosystems.

HIDE AND SEEP

The two deep-sea stations operated by Ocean

Networks Canada at the edge of the western

continental shelf have proved ideal locations for

studying the unusual ecosystems around meth

ane seeps.

Study areas

BRITISH

COLUMBIA

Pacific

Ocean

Vancouver

Island

0

75

Clayoquot

Slope

Vancouver

KM

Nanaimo

Barkley

Canyon

WASH.

Victoria

Methane seeps

Unlike deep-sea vents, which expel water that

has been superheated by volcanic activity

beneath the seafloor, methane seeps are cold

flows of methane-rich water driven by pressure

from the movement of the North American

continent.

Flipping out

Tanner crabs, foraging for food near these seeps,

rise from the seafloor on these invisible currents

of water, flip over, releasing bubbles of methane

gas from under their carapace, then return to the

seabed.

Methane

bubble

released

Crab rises

and rolls

over

Tanner crab

(Chionoecetes

tanneri)

Methane

seep

Foraging

crabs

Seafloor

IVAN SEMENIUK AND JOHN SOPINSKI/THE GLOBE

AND MAIL SOURCE: frontiers in marine science;

TILEZEN; OPENSTREETMAP CONTRIBUTORS; HIU

HIDE AND SEEP

The two deep-sea stations operated by Ocean Networks

Canada at the edge of the western continental shelf

have proved ideal locations for studying the unusual

ecosystems around methane seeps.

Study areas

DETAIL

CANADA

BRITISH

COLUMBIA

U.S.

Pacific

Ocean

Vancouver

Island

Vancouver

Nanaimo

Clayoquot

Slope

Victoria

WASH.

Barkley

Canyon

0

75

KM

Methane seeps

Unlike deep-sea vents, which expel water that has been

superheated by volcanic activity beneath the seafloor,

methane seeps are cold flows of methane-rich water

driven by pressure from the movement of the North

American continent.

Flipping out

Tanner crabs, foraging for food near these seeps, rise

from the seafloor on these invisible currents of water, flip

over, releasing bubbles of methane gas from under their

carapace, then return to the seabed.

Not to scale

Methane

bubble

released

Crab rises

and rolls

over

Tanner crab

(Chionoecetes

tanneri)

Methane

seep

Foraging

crabs

Seafloor

IVAN SEMENIUK AND JOHN SOPINSKI/THE GLOBE AND MAIL,

SOURCE: frontiers in marine science; TILEZEN; OPEN-

STREETMAP CONTRIBUTORS; HIU

HIDE AND SEEP

The two deep-sea stations operated by Ocean Networks Canada at the edge of the

western continental shelf have proved ideal locations for studying the unusual eco-

systems around methane seeps.

Study areas

DETAIL

CANADA

BRITISH

COLUMBIA

U.S.

Pacific

Ocean

Vancouver

Island

Vancouver

Nanaimo

Clayoquot

Slope

Victoria

WASH.

Barkley

Canyon

0

75

KM

Methane seeps

Unlike deep-sea vents,

which expel water that

has been superheated

by volcanic activity

beneath the seafloor,

methane seeps are cold

flows of methane-rich

water driven by pres-

sure from the move-

ment of the North

American continent.

Methane

bubble

released

Crab rises

and rolls

over

Tanner crab

(Chionoecetes

tanneri)

Flipping out

Tanner crabs, foraging

for food near these

seeps, rise from the

seafloor on these

invisible currents of

water, flip over, releas-

ing bubbles of meth-

ane gas from under

their carapace, then

return to the seabed.

Methane

seep

Foraging

crabs

Seafloor

Not to scale

IVAN SEMENIUK AND JOHN SOPINSKI/THE GLOBE AND MAIL, SOURCE: frontiers in

marine science; TILEZEN; OPENSTREETMAP CONTRIBUTORS; HIU

And the crabs are probably not alone, Dr. De Leo said. “We certainly think that some other species, including rockfish, might be doing the same thing."

While certain species have long been known to live off methane seeps, these species tend to be fixed in place, living separately from other ocean life, as though on another world. The new finding suggests the seeps may be playing a bigger role in ocean biology than originally thought, thanks to the crabs and other itinerant creatures that are dropping in to supplement their diets and then moving on.

“There are certainly a lot [of] commercially important species that hang out at seeps,” said Lisa Levin, a professor at the Scripps Institution of Oceanography in San Diego, who was not part of the study.

Recent advances in underwater mapping have shown that the seeps are a widespread phenomenon. In the past two years alone, more than 1,000 such seeps have been discovered along the Cascadia subduction zone, which runs parallel to the West Coast from northern California to British Columbia. Each seep is a patch of seafloor, tens to hundreds of square metres in size, where cold, methane rich water is flowing out due to pressure from the relentless slide of the North American continent overtop the thinner ocean crust that lies to the west.

Story continues below advertisement

The video led to a newly discovered link between the methane that is seeping out from under North America’s submerged western rim and some of the seafood that finds its way onto restaurant menus.

Ocean Networks Canada

Ocean Networks Canada operates two stations near methane seeps, both of which are hooked into an 840-kilometre-long fibre-optic loop that carries data and live video back to shore. Researchers working with the data first noticed the crabs and their flipping antics back in 2012.

“You could see that they were actively foraging amongst the bubbles,” said Sarah Seabrook, a doctoral student at Oregon State University who set about looking for a link between the crabs and the gas-guzzling bacteria.

Ms. Seabrook said she was stymied at first because when she chemically analyzed Tanner crabs that were captured at the Canadian seeps, she did not find the carbon isotopes that would be expected from geologically produced methane. Only when she looked specifically at the fatty acids in the captured crabs did Ms. Seabrook finally spot the telltale chemical signature.

“We’ve been trying to find one needle in a haystack of food sources,” she said.

Dr. Levin said the result is an important one because it shows that the impact of the seeps on the ocean ecosystem has largely been hidden until now.

The result sets the stage for a more detailed examination of life at the seeps and the way it disperses energy into the parts of the ocean environment that are used by humans.

Story continues below advertisement

“We are showing a link to a deep-sea environment that is often thought of as remote, but it’s connected with us,” Dr. De Leo said.

Report an error Editorial code of conduct
Due to technical reasons, we have temporarily removed commenting from our articles. We hope to have this fixed soon. Thank you for your patience. If you are looking to give feedback on our new site, please send it along to feedback@globeandmail.com. If you want to write a letter to the editor, please forward to letters@globeandmail.com.

Welcome to The Globe and Mail’s comment community. This is a space where subscribers can engage with each other and Globe staff. Non-subscribers can read and sort comments but will not be able to engage with them in any way. Click here to subscribe.

If you would like to write a letter to the editor, please forward it to letters@globeandmail.com. Readers can also interact with The Globe on Facebook and Twitter .

Welcome to The Globe and Mail’s comment community. This is a space where subscribers can engage with each other and Globe staff. Non-subscribers can read and sort comments but will not be able to engage with them in any way. Click here to subscribe.

If you would like to write a letter to the editor, please forward it to letters@globeandmail.com. Readers can also interact with The Globe on Facebook and Twitter .

Welcome to The Globe and Mail’s comment community. This is a space where subscribers can engage with each other and Globe staff.

We aim to create a safe and valuable space for discussion and debate. That means:

  • Treat others as you wish to be treated
  • Criticize ideas, not people
  • Stay on topic
  • Avoid the use of toxic and offensive language
  • Flag bad behaviour

Comments that violate our community guidelines will be removed.

Read our community guidelines here

Discussion loading ...

Cannabis pro newsletter