Juneau scientist explores world's largest marine canyon

Posted: Sunday, September 16, 2007

At 1,300 feet below the water's surface, in the giant Zhemchug Canyon in the middle of the Bering Sea, Juneau marine ecologist Michelle Ridgway piloted her Deepworker submarine through the squid zone.

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The foot-long, torpedo-shaped cephalopods attacked.

Ridgway dimmed her lights, but the squids were relentless. A few were even sucked into her thrusters, disabling the system.

She was forced to abort the dive, one of 25 into the largest marine canyon in the world. Northwest of Dutch Harbor and about halfway between Alaska and Russia, Zhemchug Canyon stretches more than 60 miles wide and more than 2,700 meters deep.

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For more information, visit greenpeace.org/usa/campaigns/oceans/bering-sea-tour-2007.

The area yields a significant portion of the almost 2 million metric tons of annual Bering Sea groundfish take. It's thought to be a refuge for coral sponges and other crucial marine life. But little is known about the mysterious realm.

Ridgway was part of a three-week expedition to Zhemchug and Pribilof canyons - the first recorded scientific foray into the canyon system.

Greenpeace funded the expedition, hoping to learn enough about the area to mark it as a protected zone and close it to fishing, especially bottom trawling.

Five scientists, including Ridgway, piloted two solo Deepworker submarines into the canyons to depths of about 2,000 feet. Deck teams operated a submersible down to about 3,000 feet.

"I believe that regions of the Bering Sea shelf break, including portions of the canyons, need be protected from fishing practices that destroy habitat or disrupt other key ecological functions," said Ridgway, an ecological consultant with Oceanus Alaska and advisory member of the North Pacific Fishery Management Council.

"Our suggestion is going to be to make Zhemchug Canyon and Pribilof Canyon closed to fishing," said John Hocevar, an oceans specialist with Greenpeace for the last four years. "If you're going to be trawling throughout the Bering Sea, then there needs to be some place that's a refuge for these valuable habitat to form coral sponges and other marine life."

Last winter, the North Pacific Fishery Management Council, which oversees management of federal waters off Alaska, acknowledged the canyon's diverse and productive habitat. But ultimately, it decided there was not enough information to justify protecting them.

"We took that as an invitation to go out and try to answer some of the questions and get some very baseline information," said John Hocevar, an oceans specialist with Greenpeace for the last four years.

The expedition cost almost $20,000 a day, Hocevar said. The Smithsonian and the National Marine Fisheries Service also collaborated on the expedition with groups from the private sector and a handful of universities, including the University of Alaska.

"It's pretty expensive, but when you compare that to the billion-plus industry that's operating in this area, you would think that we could find the money to do the research," Hocevar said. "The frustrating part is that we make management decisions about fishing and other uses of these areas without having a clue about what's down there."

Pribilof Canyon, 1,830 meters deep, starts 35 miles south of St. George Island. Zhemchug Canyon lies to the west.

Researchers have wanted to visit the zone because it's thought to be one of the most productive regions on the planet in terms of phytoplankton and habitat for rockfish, skates, black cod and other species.

It's also thought to be the ancient mouth of the Yukon River during the last Ice Age.

But the area's remote location and its vast size makes exploration a difficult proposition.

A former Soviet submarine engineer was part of the crew and shared a few stories about some of his military exploits.

"It's quite possible that the Soviet or U.S. military has been down there, but we don't have any record of that," Hocevar said. "They've been an awful lot of places that they're not saying."

The team conducted 25 submarine dives and eight remote-operated submersible dives. It ran transecting surveys up the slopes around the outside edges of the canyons.

The crew collected dozens of specimens - corals, sponges, anemones, shrimp and worms. Those will sent off to specialists in the United States and Europe for identification and further analysis.

"It seems like we've discovered one, if not several species," Hocevar. "And that's not surprising, given how little we know about sea life in these sea canyons."

"Even with this work, there's an awful lot more to be done before anyone can say they understand what's going on down there," he said.

Next, the team will work with the Smithsonian and world experts to identify the specimens they've collected; map the spots in the canyon depth strata where the organisms were discovered; and process underwater geological samples to discover the origin of stones dropped by seasonal sea ice and icebergs.

Ridgway will analyze video footage and some of the fish species. She also collected clods of compacted clay from the depths of the canyon. The clods appear to contain shells and worm casings which may date from the time when the canyon was the mouth of the Yukon River.

"It's obvious they're packed with paleontological remains of ancient marine life," she said. "There may be some linkage to terrestrial species in the Ice Age."

The scientists descended through upper water column layers filled with zooplankton, krill, chaetognaths and various other microorganisms.

On the sandy plateaus of the canyon, the scientists discovered drop stones. The giant stones offered a safe haven for corals, sponges and anemones and hydroids to attach to the sea's floor. That habitat had attracted juvenile rockfish, baby king crab and other species.

Sponges were packed with invertebrates and fish eggs. In some instances, Ridgway collected a sponge at 1,800 feet and brought it back to the surface to examine it in the wet lab. The larval fish eggs would hatch in her petri dish.

One of the biggest surprises was the amount of juvenile rockfish that were cavorting about nonrocky parts of the compacted sea floor.

"We usually think rockfish, especially baby rockfish, live in rocky habitats," Ridgway said. "That's not always the case. They don't have many predators so they're able to exist in a rather exposed orientation along the sea floor."

The worst surprise, for Hocevar, was how much trawl damage was evident. In some cases, he said, trawl tracks crisscrossed.

"There was one huge swath, several hundred meters, where every coral I came across was broken or overturned," he said.

Ridgway has been scuba diving since 1983, when she spent her first Permanent Fund Dividend check on scuba lessons.

In 1996, she used a Delta submarine to examine Taku Inlet as part of a Environmental Protection Agency project on the effect of mine tailing dumping on the ecosystem. In 1998, she trained to obtain a pilot's license for the Seaworker II, a precursor to the Deepworker.

The fundamental operation of the Deepworker was similar to the submarines she had piloted before. The main challenge was multitasking while attempting to navigate the dominant oceanographic currents of the Bering Sea.

In the Deepworker, the scientists sat in an 8-foot titanium pod with a 2-centimeter acrylic dome. Interior pressure was maintained at -1 pound per square inch, which meant that the crew felt negligible pressure.

Ridgway roamed as deep as 1,757 feet. Her previous depth-record was 1,500 feet, while training in Canada. Before that, she had gone as deep as 750 feet in Taku Inlet.

"You don't feel pressure," Ridgway said. "You feel cold. You feel dark. And you feel intensity."

Less than 1 percent of the planet's oceans have been examined. And though the remote-operated submersible dove down to 3,000 feet below the surface, that's only half the depth of the canyon.

"We've done more than scratch the surface, but I want to get to the bottom," Ridgway said. "I want to see the full depth profile. We need to understand how this ecosystem functions."

"One of the most interesting things that is going to come out of this is a concern about how we treat vulnerable and patchy habitat," he said. "This is an area where there is mud and silt, but the challenging part is there's also an awful lot of corals that are providing habitat for these species."

• Contact Korry Keeker at 523-2268 or korry.keeker@juneauempire.com.



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