Unsupported Browser Detected

Internet Explorer lacks support for the features of this website. For the best experience, please use a modern browser such as Chrome, Firefox, or Edge.

Joint Canada-US Deep-Sea Coral Seamount Survey Post #2

September 16, 2022

On September 6th, an international team of researchers assembled to survey deep-sea coral and sponge habitats on seamounts 300 miles offshore of the U.S.-Canada border in the Northeast Pacific Ocean. Follow this blog to learn what they discover.

photo of two people in hard hats and orange vests lowering stereocamera array overboard Deploying the stereo camera system over the starboard side of the Canadian Coast Guard Vessel John P. Tully. Credit: NOAA Fisheries/Paul Hillman.

Eickelberg and Warwick Seamounts

After our 40-hour steam to Eickelberg Seamount, the data collection begins! 

Let’s back up a second. Why are we doing this research, and why do both the US and Canada have interest in these seamounts? I mean, don’t corals grow in shallow, tropical waters near the equator?

Photo of a school of fish in clear blue sunlit water over coral reef
Fish swim above a coral reef in the Caribbean. Credit: Tom Moore

Shallow Water Corals vs. Deep-Sea Corals

The tropical corals that often come to mind when talking about corals and coral reefs do live in shallow waters, because they depend on sunlight. They have a mutual relationship with a type of algae called zooxanthellae. The coral provides carbon dioxide (through respiration) and a place for the algae to live inside its individual polyps. In turn, the algae provide nutrients (sugars, fats, and oxygen from photosynthesis) to the coral polyps. However, deep-sea corals live deeper than light penetrates, and therefore don’t house zooxanthellae. They gather nutrients the more familiar way—by eating. Individual polyps look like little anemones and capture nutrients and tiny animals as they float by.

Close-up photo of multiple coral polyps
Most corals are made up of hundreds to hundreds of thousands of individual coral polyps. Credit: NOAA

And these deep-sea corals don’t build reefs but, like tropical corals, do provide unique and important habitat on an otherwise rocky or sandy seafloor. These corals often grow tall so the polyps can reach up into the water column to feed. This three-dimensional growth provides habitat that fish, crab, and other animals can duck under, hide behind, or cling to. Sponges also grow in much the same way. The benefits of this living structure are what this expedition aims to understand more clearly. We also hope to better understand the presence/absence of deep-sea coral and sponge on these seamounts, and how the environment affects their distribution in the Northeast Pacific.

Colorful pink and white striped rockfish swim around and under a large feathery yellow coral with sea urchins along the right side.
Rockfish swimming around deep-sea coral habitat in Glacier Bay, Alaska. Credit: NOAA Fisheries

More Goals of this Research

The team is also looking at how fishing impacts the deep-sea coral and sponge habitat in order to come up with suggestions for better ways to fish while not damaging the habitat that some species depend on. And that’s why Canada is particularly interested in these seamounts. While these are outside of the Exclusive Economic Zone for any country (EEZs extend to 200 miles offshore of a country’s coast), Canadian fishermen operate the only active fishery out here. They sustainably fish along the bottom using longlined pots to target sablefish (black cod).

And why is NOAA’s Alaska Fisheries Science Center interested in habitat off the coast of Washington State? Because we are interested in how deep-sea corals are linked along the coast of British Columbia from Washington to Alaska. These seamounts may be the genetic link or distribution pathway by which these corals and sponges disperse from north to south. This research aims to understand this hypothesis further.

Map showing locations of seamounts in U.S. and Canadian waters in the Northeast Pacific Ocean
Map of eastern North Pacific Ocean seamounts showing the five seamount complexes to be surveyed on this cruise in bold text (Eickelberg, Warwick, Corn, Cobb and Brown Bear). Credit: NOAA Fisheries

What it comes down to is that we know far less about deep-sea corals than tropical corals. We’ve only just begun to explore deep-sea coral and sponge habitats and their supporting role for the larger deep-sea ecosystem. And this habitat is hard to reach. We’re talking 150-1000 meters for these seamount sites. 1000 meters is more than half a mile!

Highlights from September 9-10

So let’s get down to the nitty gritty. What are seeing out here? These are exciting times because Eickelberg Seamount has never been visually surveyed before, and Warwick only once in 2002. 20 years ago!

Tall coral with brittle stars and seastars on rock underneath and bright red fish to the right on dark seafloor
Coral habitat attracts diversity like seastars and this thornyhead rockfish (likely shortspine thornyhead). Warwick Seamount, depth ~590 meters. Credit: NOAA Fisheries
Coral and sponge among an array of brittle stars on a rock wall on the dark seafloor
Coral and sponge growing on a rock wall covered in brittle stars. Warwick Seamount, depth ~640 meters. Credit: NOAA Fisheries
Purple and orange anemones in front of an array of corals, brittle stars, and seastars on rocky bottom of the dark seafloor.
Some of the thickest corals we saw on Eickelberg or Warwick are in the background. The purple animals in the foreground are sea anemones. Warwick Seamount, depth ~530 meters. Credit: NOAA Fisheries

Corals and sponges! More than we expected too. When talking with Dr. Chris Rooper over lunch (Chris is the chief scientist from Fisheries and Oceans Canada), he was pleasantly surprised to see so much coral at these sites. From previous modeling and based on the limited information we do have, he was expecting more sandy bottom habitat (sandy bottom on seamounts is often from currents depositing sand on these submerged, rocky islands). And with rocky bottom comes places for corals and sponges to attach and grow.

Corals on rock among a sandy background with small fish hovering over sand.
Corals grow from hard surfaces like this rock outcropping on a sandy bottom. A grenadier fish hovers over the sand in the center of the image. Warwick Seamount, depth ~640 meters. Credit: NOAA Fisheries.
Tall coral on rock scattered with brittle stars lit up against dark background
Coral with sea stars and anemones along the rock surface. Brittle stars are one of the most numerous animals seen at these depths. Warwick Seamount, depth ~530 meters. Credit: NOAA Fisheries.
Photograph of rock with large, white, perforated, vase-shaped sponge on a rock.
Sponges create cavities that provide shelter for smaller animals. The patterns on the sponges are intricate and mesmerizing. This glass sponge was seen on Warwick Seamount, depth ~670 meters. Credit: NOAA Fisheries.
Close-up photograph looking down into a large, white, vase-shaped sponge on dark seafloor.
Close-up on a glass sponge showing the inner cavity and the porous structure. Warwick Seamount, depth ~670 meters. Credit: NOAA Fisheries.
Tall corals and brittle stars on a large round boulder on dark seafloor.
An otherwise bare rock face populated with corals creating vertical structure to this habitat. Warwick Seamount, depth ~530 meters. Credit: NOAA Fisheries.

As you can see from the images, the coral is not dense, but there is a relative high presence. In comparison from past surveys in Alaska waters, the Aleutian Islands has very high density with corals on basically every rock. The Gulf of Alaska has more sand bottom, so relatively low presence of coral and sponge habitat, while the Bering Sea shelf is mostly sand or soft bottom.

Upon first glance, this means that these two, relatively unexplored seamounts may be even more special than previously thought. But these are only the first two days and the smallest sites, so let’s see what the next three seamounts bring. We’re headed to Corn Seamount next, followed by Cobb, and finally Brown Bear.

Follow the next blog to see what else we find, more details about the innovative stereo camera system, and why it’s used vs. other methods of sampling.

Photograph of large white boulder with various corals and other invertebrates on dark seafloor.
Corals create habitat and attract life. Check out the squat lobster hiding under a boulder near a sea anemone. On top of the rock, the long sausage-looking thing is a sea cucumber. Eickelberg Seamount, depth ~770 meters. Credit: NOAA Fisheries


Previous: Joint Canada-U.S. Deep-Sea Coral Seamount Survey Post #1 Next: Joint Canada-US Deep-Sea Coral Seamount Survey Post #3

Meet the Blogger

Last updated by Alaska Fisheries Science Center on November 08, 2022