Remarkable diversity of life found in sea canyons off Northeast coast
The deep-sea canyons off the Northeast coast of the US are largely unexplored. A 36-day expedition currently under way is finding a rich trove of marine life.
Boston — Roughly 100 miles seaward of the beaches, boardwalks, and marinas along the Northeastern coast lie darkened canyons where corals and sponges cradle shark eggs, russet-red brittle stars wrap their arms around the white stalks of octocoral, and wide-eyed bobtail squid peer back at undersea cameras as if to say: Hey, you lookin' at me?
These are among the denizens scientists are finding during a project known as the 2013 Northeast US Canyons Expedition.
For all their proximity to some of the world's top marine research centers, the region's deep-sea canyons remain largely unexplored. The 36-day cruise, which began July 8, is designed to gathering images from 11 canyons and one seamount, as well as gather basic data on changes in seawater salinity and temperature with depth. The expedition is exploring these features at depths ranging from 500 to 2,200 meters (1,600 to 7,000 feet).
The goal is to provide an initial look at the canyons' inhabitants and form some initial ideas about how the canyons' ecosystems function, explains Tim Shank, a marine ecologist at the Woods Hole Oceanographic Institution in Woods Hole, Mass., and one of the lead scientists for the expedition.
The results would help set up a second generation of expeditions to understand these workings in greater detail – with an eye toward managing what is likely to be a vital marine resource, he says.
Expeditions exploring canyons in the western Pacific have shown that they harbor a rich mix of species and that corals and sponges in the canyons act as relatively safe nurseries for young fish, just as corals closer to the surface do. The expedition to canyons off the Northeast coast aim to find out if these undersea features play an equally important ecological role here.
In the Northeast, "we've been able to obtain the fish we need without having to go deeper, into these canyons," he says. Now, fishermen can harvest from depths as low as 2,000 meters, giving them access to areas they couldn't reach in the past – including the canyons.
The National Oceanic and Atmospheric Administration (NOAA) and other stakeholders, "are saying: Wait, before we go and open up everything for fishing, let's go see what's out there," Dr. Shank says.
In addition, researchers are looking at the potential for undersea landslides along the continental margin, events that can triggered tsunamis.
In November 1929, for instance, a powerful undersea earthquake struck some 280 kilometers south of Newfoundland, triggering an undersea landslide that involved an estimated 200 cubic kilometers (48 cubic miles) of material. The tsunami snapped undersea telegraph cables and killed 27 people in Newfoundland and one person in Nova Scotia.
"There's a lot of evidence of past, large submarine landslides," says Jason Chaytor, a marine geologist at the US Geological Survey's Woods Hole Science Center. "We're trying to understand how old those landslides are" and whether the mechanisms that triggered them are still active.
Energy resources also are on the agenda. During the first of two legs of this summer's expedition, researchers spotted the northernmost undersea methane seep yet discovered along the eastern seaboard – complete with communities of marine organisms that feed off the methane. Not only was methane bubbling out of the sea floor, but the surface sediments on the flood held ice-like mixtures of methane and water mixtures, known as methane clathrates, frozen by the combination of frigid undersea temperatures and the enormous pressure on the sea floor.
The expedition is using NOAA's research ship Okeanos Explorer and the agency's newest remotely-operated undersea vehicle, the Deep Discoverer. This is Deep Discoverer's maiden expedition after clearing its engineering trials in May.
Dozens of researchers in the US and France are participating via telecommunications links that allow them to see what the undersea rover is seeing as it takes its images, share insights into what the images may be revealing, and plan next steps for the mission. The approach allows more researchers to play an active role in the expedition than would be the case if the participants were limited to the relatively sparse bunk space on a research ship.
Going in to this expedition, Texas A&M University researcher Brendan Roark says he was not a big believer in such "telepresence" cruises. "But ultimately, it was fantastic because I learned a lot more by having conversations with anywhere from 15 to 30 scientists," he says.
Even before the expedition's end Aug. 16, he and other members of the team have marveled at the some of the unique views they've been given of these little seen and poorly understood environments.
One of the key features reef systems in these canyons seem to share is remarkable longevity. Biological processes work more slowly at 1,000 meters than they do at the surface. Deep-sea corals in canyons can live for as many as 4,500 years.
They represent potentially rich archives of information on past climate and ocean conditions in the region, says Dr. Roark.
But once destroyed, the reef communities may take decades to centuries to recover. Little is known about that process because, until now, the deep-sea reefs researchers have seen have been mature ones.
"On the second day of this cruise, we found an area that has some recent slumping, a landslide, and we saw a lot of different coral species that were very small. We haven't seen that before," says Shank. "Many, many were there and they were all six to eight inches tall. That tells us that these are relatively new."
How new, no one knows because so little is known about the growth rates and life cycles of these species, he says.
The canyons the team has explored so far have been remarkable for the diversity and amount of new life, says Andrea Quattrini, a PhD candidate in marine science at Temple University in Philadelphia and one of the expedition's lead scientists.
In addition to the new corals, "we saw several octopus guarding eggs, in one case a sponge with bobtail squid eggs – in one case we saw one hatch," she says. And in many of the canyons the Deep Discoverer sent back images showing deposits of catshark and skate eggs.
"I was surprised at the amount of new life being formed," she says.
Researchers also noted with some amazement the presence of crabs the size of quarters occupying small bottle-brush-like coral. They are unique to the coral, typically appear in male-female pairs, and some have a juvenile as well.
"It's like a family unit," says Shank of the species. A couple's hunt for a coral to occupy can be like hunting for a specific lamppost out of all the lampposts in Manhattan. "Somehow they get there, a male and a female, and they produce offspring. It's just amazing that life is sustained and maintained in this way."