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Joint Canada-US Deep-Sea Coral Seamount Survey Post #5

November 08, 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.

In a large room, several scientists sit on chairs looking at different screens showing a black and white image of black coral on the seafloor. In the ship’s wet lab, the science crew is glued to the monitors during a drop-camera survey on Brown Bear Seamount, one of the seamounts that has never been seen by humans before. This was one of the final surveys of this expedition during which we watched live images of black coral. Credit: NOAA Fisheries/Paul Hillman.

Last Stop: Brown Bear Seamount

On September 16th, we arrived at Brown Bear Seamount—our final survey destination and another site where no underwater imagery had been collected before. The 16th and 17th marked days 10 and 11 on the survey. While fatigue began to set in, the crew was fired up to see what Brown Bear had to offer.

Dozens of whip-like orange-colored black coral rise up from the seafloor and a gray grenadier fish hovers among them. Mixed in are also stalked glass rope sponges.
Unique to Brown Bear Seamount, we encountered dense groupings of Stichopathes, a type of black coral seen here. Many critters like this habitat, including this grenadier fish. Mixed in with the black coral are also sponges, likely stalked sponges called Hyalonema, or glass rope sponges. Brown Bear Seamount, depth ~700 meters. Credit: Fisheries and Oceans Canada/NOAA Fisheries.

When I asked the survey team what their impressions were following the photo transects on Brown Bear Seamount, the general consensus was that there was a lot of coral! And it was interesting seeing more diversity here, like the black corals pictured above.

The depths of Brown Bear were deeper than Cobb, where we saw less coral—though that may be partially due to fishing pressure. It was also right in line with what we saw on Corn and Warwick Seamounts, which both had similar depth profiles. So, in this part of the world, we may be seeing a sweet spot for corals in this 450m to 750m depth range. Of course, these are just preliminary observations. Official conclusions will need to come after extensive analysis of the data. But it’s interesting to notice these patterns.

Looking down on a yellow, bugle-shaped glass sponge and a folded white sponge. A couple whip-like black corals dangle in the water above the sponges.
Two types of glass sponges growing together, with black corals dangling in the water above them. Brown Bear Seamount, depth ~670 meters. Credit: Fisheries and Oceans Canada/NOAA Fisheries.

Another striking observation was the diversity and presence of sponges. In the image above, there are two very different species of glass sponge right next to each other. Below the bugle-shaped sponge that appears to be growing in a spiral pattern, notice the more delicate, folded sponge.

The scientists were fascinated with what they found on every dive. After we return home, the next step is deep analysis of these survey images. These will be coupled with environmental observations to learn more about what else lives at these sites and the conditions that are present.

eDNA: Environmental DNA Sampling

As alluded to above, it’s not just visual data of the seafloor habitat that we collected during this expedition. At every site where the drop-camera was deployed, the team also captured a sample of seawater at the start of the camera transect. When the camera was brought back to the deck of the ship, some team members downloaded the images and replaced the camera battery, while others transferred the water sample to sterile plastic bags.

On the left, and scientist hovers controls a computer that's plugged into the drop-camera. On the right, two scientists collect water from a Niskin bottle on the back deck of the ship.
On the left, Chris downloads images from the drop-camera after a survey. On the right, Janelle, Devon, and Pam collect water samples captured at depth for eDNA analysis. Credit: NOAA Fisheries/Paul Hillman.

The water sample is then filtered in the lab with a specific filtering system that targets eDNA, or environmental DNA. eDNA is just as it might sound. It’s DNA that’s floating around in the environment. Why is that useful? Because DNA is unique to animals and plants at the species level. And the individual samples of DNA from the water sample can be sequenced, i.e. mapped, which in turn can be matched up with other known sequences that have been cataloged in libraries over decades. Ultimately, eDNA analysis can suggest what other organisms live at or near that specific site.

Two scientists poor water from sterile plastic bags into filters.
In the wet lab, the water sample is filtered to extract the eDNA for later analysis. Credit: NOAA Fisheries/Paul Hillman.
A scientist uses forceps to place a folded filter sample into a small vial.
Once the eDNA water samples are filtered, the filter paper is put into a vial for DNA sequencing at specialized labs in Seattle. Credit: NOAA Fisheries/Paul Hillman.

This is especially useful for these camera surveys where we are only getting a 15-minute snapshot along a single transect at a site. Who knows, there could be a shark or giant squid that gets spooked by the camera rig, which we never see. This also holds true for many small or microscopic animals that we would never pick up with the camera survey. The eDNA results can give us a much more comprehensive analysis of all the organisms that make up these deep-sea communities. It is another useful tool for management.

Two images of an octopus squid side by side. On the left, the orange squid faces down with tentacles trailing behind it. In the right image, the squid's hood is flared out and looks like a spade, while the tentacles are splayed out above.
Close to the bottom, the drop camera captured a whole sequence of shots of this octopus squid by total chance. Who knows how many other species were behind or to the side of the drop-camera during surveys? eDNA will help us get answers to that question. Brown Bear Seamount, depth ~580 meters. Credit: Fisheries and Oceans Canada/NOAA Fisheries.

Oceanography Data for the Big Picture

The other big science effort taking place on this survey was oceanographic sampling. Scientists from Fisheries and Oceans Canada worked the night shift, making this a 24-hour operation. Once the underwater camera was secured and put to bed for the night, the oceanography team jumped into action. At dusk they were dunking the first bongo nets. The nets get their name from a resemblance to bongo drums. Their purpose is to collect the zooplankton (tiny suspended animals) in the water column at a given site.

A bongo net is lowered next to the stern of the vessel while a scientist looks over the rail. The bongo net is two circles side by side facing up, with tapered nets trailing below them.
The bongo net is deployed over the stern of the vessel. Credit: NOAA Fisheries/Paul Hillman.

The mesh that makes up the bongo nets tapers from the opening to the cod end, where the samples are collected. The apparatus is dropped to the bottom slowly and pulled back up quickly, and the mesh size of the nets and cod-end allow water and very small particles, like phytoplankton, to pass through while isolating the zooplankton. Scientists analyze these samples for distribution and abundance. Here they often found krill (aka whale food!), copepods, larval fish and crabs, and more.

Looking down into the cod end, which is a white cylinder that has been detached from the bongo net. In the cod-end is a brown slurry of microscopic animals.
Bongo net sample in the cod-end, which contains a slurry of biological life. Credit: NOAA Fisheries/Paul Hillman.

Similar to the eDNA studies, the oceanography team also sampled the water, but for different purposes. They used this CTD rosette with multiple collection bottles. Each bottle shuts at a unique depth and the water samples are analyzed for the oceanographic properties, such as salinity, dissolved oxygen, nutrient concentrations, and more. The rosette was also affixed with instruments that measure conductivity, temperature, and depth, which is where the CTD abbreviation comes from.

Looking out over the starboard side of the ship, a crane lowers a large CTD rosette into a blue ocean.
The CTD (conductivity, temperature, and depth) rosette is deployed over the starboard side of the ship. Credit: NOAA Fisheries/Paul Hillman.

These samples will give us a snapshot of conditions observed on this expedition, and feed into long-term data sets to help understand any changes over time, including any signs of climate change. This information is correlated with that from the drop-camera surveys to understand what environmental conditions exist at the time of this survey. This will serve as another data point and baseline for understanding any changes we may observe to these deep-sea coral communities in the future.

The CTD rosette is lowered by the crane onto the starboard side of the vessel, while a scientist guides it into place.
The CTD rosette is recovered to the deck. Credit: NOAA Fisheries/Paul Hillman.
One scientist extracts a water sample from a Niskin bottle on the CTD rosette while another records data into a notebook.
Steve collects a water sample from the Niskin bottles on the CTD rosette, while Cindy records data. Credit: NOAA Fisheries/Paul Hillman.

More Images from Brown Bear & Thank You!

As we conclude this blog, we hope you enjoyed learning about this Joint Canada-U.S. Deep-Sea Coral Seamount Survey. The international collaborative nature of this survey was a special experience to be a part of, and we owe a huge debt of gratitude to the officers and crew of the Canadian Coast Guard Vessel John P. Tully. Their creativity and problem-solving were exceptional, and we greatly appreciate their dedication to the science mission. There were many overtime hours worked and everyone was nothing but supportive.

The captain, officers, and crew pose on the back deck of the Canadian Coast Guard vessel John P. Tully.
Thank you to the officers and crew of the CCGS John P. Tully! They were outstanding! Credit: NOAA Fisheries/Paul Hillman.

If you’re interested in learning more about NOAA’s deep-sea coral and sponge habitat research, check out this blog series from July’s survey in the Gulf of Alaska, the Deep-Sea Coral Habitat page, and, of course, the NOAA Deep-Sea Coral Data Portal.

Finally, we’ll leave you with more of these first images from Brown Bear Seamount. Enjoy!

Rocky habitat with sponges, corals, and squat lobsters living on it.
A diversity of life on Brown Bear seamount including different species of sponges, corals, squat lobsters, and more. Brown Bear Seamount, depth ~770 meters. Credit: Fisheries and Oceans Canada/NOAA Fisheries.
Dozens of whip-like black coral rise from the sea floor with orange thornyhead rockfish living beneath them.
These whip-like black corals may not look like they provide much habitat, but clearly they do. Several species of fish were observed in this habitat, as well as sponges, sea cucumbers, and more. Brown Bear Seamount, depth ~700 meters. Credit: Fisheries and Oceans Canada/NOAA Fisheries.
Rocky bottom rises from left to right with pink/orange fan-shaped hydrocoral extending from a few surfaces. A couple squat lobsters also on the rocks.
Hydrocoral extends out from rock habitat, providing variability and structure to this rocky habitat. Brown Bear Seamount, depth ~700 meters. Credit: Fisheries and Oceans Canada/NOAA Fisheries.
A large yellowish coral skeleton covered in yellowish colonial zoanthids extends from a large boulder. Brittle stars are scattered on the rocks below.
A new sighting for this crew is shown here: a coral skeleton covered in colonial zoanthids, which are a relative of corals, anemones, and jellyfish. Brittle stars live on the rocks below. Brown Bear Seamount, depth ~590 meters. Credit: Fisheries and Oceans Canada/NOAA Fisheries.
A white sponge extends upward like and arm with the hand folded forward.
This sponge was remarkable, looking to me like some sort of alien sentinel or sock puppet. Brown Bear Seamount, depth ~590 meters. Credit: Fisheries and Oceans Canada/NOAA Fisheries.
A large yellowish fan shaped coral extends up from the rocky bottom towards the camera.
A large, branching bamboo coral, reaches up from a rocky bottom. Brown Bear Seamount, depth ~590 meters. Credit: Fisheries and Oceans Canada/NOAA Fisheries.
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Last updated by Alaska Fisheries Science Center on November 08, 2022