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Off Hawai‘i’s coast, an unexplored undersea mountain reveals its secrets

© Luana Luna

A dumbo octopus (Grimpoteuthis sp.) swims on the Cook Seamount. Filmed on September 6, 2016, from the submersible Pisces V on a Conservation International and Hawaii Undersea Research Laboratory (HURL) expedition to explore Hawaiian seamounts.

Editor’s note: A recent deep-sea expedition off the coast of Hawai‘i is shedding new insights into the diversity of life on “seamounts,” undersea mountains that remain largely unexplored. Seamounts, formed by volcanic activity, are believed to cover some 18 million square miles of the planet — yet little is known about them.

A week after President Obama announced the creation of the world’s largest marine protected area in far northwestern Hawai‘i, the expedition — led by two senior scientists at Conservation International — became the first to survey the Cook Seamount, a mere 70 miles off the coast of the main island. The submersible captured photos and video of species rarely seen — including a species of coral that may be new to science.

In this interview recorded during the expedition, CI scientists M. Sanjayan and Greg Stone discuss their discoveries, the challenges of deep-sea exploration, and the critical importance of seamounts to ocean health.

Sanjayan (S): I’m here with CI’s chief ocean scientist, Greg Stone, just off the Big Island of Hawai‘i, and we’re about to do another dive on a seamount. Greg, why are seamounts so fascinating to you?

Greg Stone (G): They first captured my attention when I realized they were mountain ranges under the ocean that rivaled — exceeded in some ways — those on land. Think about it: You would never dream that there were these structures in the ocean depths that rise 10,000 feet (4,000 meters) from the sea floor. I get this feeling when I am down there in the sub — from the exploration and discovery, the companionship — and I think, “I am underneath a mile of ocean water, I am surrounded by ocean and I am in a place no one has ever been.” That is one of the sweetest feelings I ever get.

S: Are there seamounts in every ocean? I would imagine that most seamounts have been mapped and we know where they are at this point.

G: There are estimated to be about 10,000 seamounts and they’re in every ocean, though most of them are in the Pacific. We have a pretty good idea of where most of them are, but not all of them — some of them we only know about because satellites have detected gravity anomalies from space.

S: On Wednesday, you and I got to do a submersible dive on the McCall seamount and we were told that no one had ever explored it via submersible before. I find that unbelievable given how close it is — we were only about 70 miles from the coast!

G: There are actually only several dozen seamounts that we have visited, meaning a person has gone down in a submersible or we have sent down a remotely operated vehicle for a close-up view.

An adult Pacific sleeper shark (Somniosus pacificus) seen from the Pisces V. Shot by Pisces V on September 8, 2016, during the Conservation International and University of Hawaii Undersea Research Laboratory seamounts expedition.

G: The equipment to get to them is expensive. The ship we are on — the Ka’imikai-O-Kanaloa from the University of Hawai‘i’s Undersea Research Laboratory — and it submarines cost US$ 50,000 a day to use.

S: There are very few of these deep-sea submersibles like the one we’re on. They’re expensive and difficult to operate; it takes a small army to launch and recover them. Why can’t we just use robots to explore seamounts? Why do you feel like we need to go down there and see for ourselves?

G: There is a place for robots; however, we have not yet been able to replicate the ability of the human brain or the human eye to take in and interpret information. There are discoveries and understandings of things down there that can only be had by having a person in the submarine looking out the portholes, seeing things a robot might not see and making onsite decisions.

S: When we were down there yesterday, in the process of collecting coral samples our coral scientist alerted us to the fact that they were most likely new to science. Doesn’t that boggle the imagination that there are so many things down there that are new to science?

G: Believe it or not, it’s not that surprising to me! Think about it this way: Our understanding of the ocean is about one hundred years behind our understanding of land because we haven’t had the same access to the water. The ocean has this beautiful serene barrier of all of that water out there — and it’s just now that we’re beginning to get down into the ocean, like we got into the rainforests a century ago.

Purple chimera (Hydrolagus purpurescens) swimming at McCall seamount off Hawai’i’s southwest coast. Shot on McCall Seamount by Pisces V on September 7, 2016, during the Conservation International and University of Hawaii Undersea Research Laboratory seamounts expedition.

S: What are the most surprising things you’ve seen on these dives this time around? It was much more rugged than I thought I expected to hit a sandy floor and it wasn’t like that. It looked like something clawed out of the side of the mountain, or spewed out.

G: I was surprised by the clarity of the water. I have been on a lot of deep sea dives and this was the clearest water I have ever seen. It has certainly lent itself to providing us a spectacular sea-floor scape. I felt like I was coming down on top of the Swiss Alps. I was also surprised by signs of some traumatic movement of material down there — not from 80 million years ago when these were formed — but from rock falls and boulders that had clearly rolled at one time. I am trying to figure out what is the mechanism that has been doing that. I think it is probably periodic earthquakes.

S: Why are oceans — and deep sea exploration — so important?

G: The oceans are the key life support system on earth. We do not understand how they work. We do not understand the vitality of the deep sea, which is connected to the shallow water where we are.

S: Is it also about helping to prioritize our focus and our energies on the high seas? It’s easy enough to know where to conserve on coastlines, but you look out there and it’s a big vast ocean — so are we trying to identify these hotspots in the oceans?

G: You hit the nail on the head. The world has finally turned its attention to the high seas. The high seas are the area that nobody owns, it’s the last commons on earth. They make up 64 percent of the ocean, or 43 percent of the Earth’s surface. The UN has just decided that they are going to create a sustainable plan for the high seas. What are they going to do? We don’t know yet, but seamounts, as you said, are a great place to start.

S: What would your wish be for the high seas regarding seamounts? For example, if you could read a headline four years from now at the next World Conservation Congress?

G: ‘The UN and international coalition of groups have committed to protecting 100 high value seamounts in the high seas by 2025.’ I would go ahead another 15 years and say the world should ultimately protect at least half of all the high value seamounts in the ocean. Let’s start by picking one country with significant sea mounts important to fisheries and conservation and protect them.

S: Seamounts are that important to ocean productivity?

G: They are that important to productivity because they support pelagic species — like the huge schools of tuna that we fish. They support other fisheries too, like orange roughy and many other species. But as important as fisheries are, seamounts support really unique forms of life found nowhere else and we are learning more and more about the essential and almost magical DNA solutions we are finding in marine plants and animals. We have already found in the ocean a painkiller that is more effective than morphine and not as addictive.

M. Sanjayan is executive vice president and senior scientist at Conservation International. Greg Stone is executive vice president of Conservation International’s Center for Oceans.

Sophie Bertazzo is a staff writer at Conservation International.

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