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Deep-ocean research off Bermuda maps a mountain and its ‘algal forest’

“The deep ocean is the beating heart of our planet and our most critically important ecosystem,” says Oliver Steed, mission director.

A Triton probes the slopes of the Argus Seamount.
Courtesy of the Nekton Mission and the XL Catlin Deep Ocean Survey

Anyone with an interest in deep-ocean exploration or seagoing adventure will likely find something to admire in this week’s first reports from the Nekton Mission’s work off Bermuda.

Using a pair of $2.2 million Triton submersibles that can carry a two-person crew to a depth of 1,000 meters — and a remote-controlled robot camera than can dive twice as far — the team spent much of last week exploring the slopes of the Argus Seamount.

A seamount is a sort of mountain that rises high above the seafloor, but not high enough to become an island. There are perhaps 100,000 of these features throughout the global ocean, Nekton scientists say, but fewer than 40 have undergone any sampling of their living communities.

The Argus’ upper reaches are in the so-called mesophotic zone, a lateral band between the lightless depths and the bright subsurface waters. A rich array of plants and animals live here, some dependent on sunlight and some not, but all increasingly tested by various pressures of degradation, which adds to the zone’s scientific interest.

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Alex Rogers, a marine zoologist at Oxford University who is serving as Nekton’s chief scientist, describes the key find so far in this way:

We have discovered a new mesophotic algal forest with almost total coverage of dense growth. This nutrient-rich algae is crucial as it feeds the deep sea just like a deep ocean ‘pasture’.

This creates an abundance of healthy mesophotic corals which could provide a refugia for shallower reefs closer to Bermuda, helping to repopulate those areas damaged by bleaching and acidification and rebuilding the resilience of the surrounding ocean.

It has long been said that we know less about Earth’s ocean depths than about the surface of its moon but nowadays, thanks to advances in space exploration, the comparison is more likely to be with the face of Mars.

Where few have gone before

Amazingly, Nekton can claim to be only the third mission to carry human observers so far down.  (The first was in 1960’s Nekton Project, from which the current endeavor takes its name; France’s Jacques Picard and the U.S. Navy’s Don Walsh rode the bathyscaphe Trieste into the Mariana Trench.)

Below the upper-level algal forest, the Nekton team reports, the slopes were found to hold gardens of black coral, communities of sea urchins, hermit crabs and other animals. Still farther down were gardens of  twisted wire corals, hydrocorals and moray eels.

Establishing a documented baseline of ocean health and degradation pressures is the Nekton Mission’s key objective, and that’s what attracted significant financial support from an Irish-based global insurance company called XL Catlin, which reasons that it’s hard to insure against risks you don’t understand.

Some of the pressures listed on the Nekton site:

Ocean acidity has increased by about 30 per cent since the beginning of the industrial revolution and the occurrence of dead zones (hypoxic, low oxygen areas) has doubled in frequency every 10 years since the 1960s.

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More than 28 percent of global fish stocks are unsustainably fished and, on the current trajectory, many of the world’s marine species may be on the brink of extinction by 2100.

“The deep ocean is the beating heart of our planet and our most critically important ecosystem,” says Oliver Steed, mission director and co-founder of its nonprofit parent. And yet, he told New Scientist recently, “we have better maps of Mars and the moon than we do of our own seabed.”

“Discoveries like these on Argus Seamount are evidence of how little we know and how important it is to document this unknown frontier to ensure that its future is protected before it is too late.”

Steed has a background as a broadcast journalist with a bent for exploration in remote places, as well as a gift for quotable phrasing — that “beating heart of our planet” line is popular with reporters who write about the work — and for telling the mission’s story in self-produced video (see links at end).

What a Triton ride is like

And he has been savvy about lining up coverage in venues like Forbes magazine, where contributing writer Jim Clash talked last week about his excellent ride into the deep on one of Nekton’s Tritons:

As we dropped from the surface at the rate of about 60 feet per minute, I relaxed as the ocean’s color went from green to blue to dark blue to black. We had to use the sub’s lights to see. At 280 feet, the Bermuda plateau fell away and angled down a slope at about 40 degrees. The surface, crusted with rough coral and rock, looked like craters on the moon as we continued to descend.

When we hit 1,000 feet down, I took an obligatory photo of the depth gauge. First, we spied some beautiful yellow coral, which looked like ferns growing out of the bottom. Lahey worked hard to maneuver a piece of it into the sample basket via a robotic arm. We found what looked to be a rare orange roughy fish — likely more than 100 years old — a yellow moray eel and plenty of wire coral. We also saw small pink fish with yellow dorsal fins and tails that may be a new species!

The Canadian government is also a major collaborator in this portion of Nekton’s work, which is focused on the North Atlantic’s Sargasso Sea and an area off Nova Scotia as well as Bermuda. So are some two dozen Canadian scientists from a range of government agencies and academic institutions.

The Coast Guard has lent the Hudson, its venerable ocean-going survey vessel, which is equipped for a range of data gathering that Ellen Kenchington, a marine ecologist and geneticist, described for the National Post last week:

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We have a multi-beam sounder (a sonar device), which will take fine-scale detail of depth across the sea floor. Nekton are funding a remotely operated vehicle, which will go down to 2,000 meters. It has an arm, which means we can not only see the sea floor, but we can take samples. The Canadian Department of Natural Resources is lending us their drop camera, which will go down to 4,000 meters.

We have a nice set of tools. What’s unusual about this mission is we’ll be using them all at once, to get an index of ocean health by measuring the water column and the sediment all at the same time in a few different places. We can get some baseline information.

Other instruments aboard the Hudson can measure things like temperature and conductivity at depths up to 5,000 or 6,000 meters, she said, and “we’ll be going that deep all the way from Halifax to Bermuda, following traditional oceanographic lines. We can take these measurements and use them to help inform the larger work that’s going on related to the Gulf Stream, climate change — its effect on all of that.”

And then there are some surface features that do not lack for interest, like the mat of sargassum seaweed for which the Sargasso Sea is named, and which is becoming heavily burdened by plastic and other ocean literature. Kenchington explained:

There’s a brown seaweed that grows along the inter-tidal rocks, and you can walk on it at low tide. In that same seaweed family, there’s a variety that has little air bladders that help it to float. It forms a big mass over the surface. It’s not continuous, but there’s an awful lot of it.

All of the eels in the North Atlantic Ocean go (to the Sargasso sea) to spawn, and then go back into the rivers from Europe and North America. Baby turtles use that as a nursing area. There’s specific life that uses that seaweed mat out in the middle of the ocean to live.

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The homepage for the Nekton project is here, an interesting animation video of the submersibles in action is here; another video of the team at work, not always absorbed in somber scientific reflection, is here.