Teeming with life, thanks to methane

MARINE ECOSYSTEMS

Just off New York City lies the Hudson Canyon, a deep gash in the seabed that runs for hundreds of miles. Charter boats and commercial fishermen have long known that the canyon’s headwaters swarm with tuna, swordfish, monkfish, tilefish, red crabs and other sea life. Now, scientists have discovered a surprising potential reason for at least part of the canyon’s riches – methane bubbling up from the seabed.

A team from Rutgers University and the National Oceanic and Atmospheric Administration has made three trips to the canyon since 2007 and is preparing another voyage next month.

It has already found high levels of methane in the waters and tracking chemical and geological clues, now sees the natural gas, which is associated with oil deposits, as a possible first meal in a long food chain. On the coming expedition, the team plans to use a robotic submersible equipped with a camera to photograph areas of the floor and sides of the canyon for the first time.

The scientists hope to gather evidence of deep creatures that live directly and indirectly on the methane, perhaps including clams and crabs, mussels and tube worms. Such bizarre ecosystems occur globally. Oil and gas seeping out of the Gulf of Mexico seabed result in riots of deep life, as do petrochemical seeps off Angola, Chile, Indonesia, Peru and Trinidad. But scientists have never found such habitats in close proximity to New York City.

Chemosynthetic ecosystems
The dark ecosystems are known as chemosynthetic because the microbes that serve as their foundation derive their energy from chemicals, in contrast to plants that use sunlight for photosynthesis.

“The big find would be a chemosynthetic ecosystem,” Peter A Rona, a marine scientist at Rutgers who is a leader of the expeditions, said in an interview. “Someone once said, ‘You stick your toe in the water and you’re in a wilderness,”’ Rona noted. “It’s true.”
Roughly 10,000 years ago, the warming earth sent glaciers retreating northward. The melting ice resulted in churning water that rushed seaward heavy with rocks and debris. Scientists say the torrent cut the Hudson Canyon, its gash up to three-quarters of a mile deep – almost as deep as the Grand Canyon.

The big drop-off starts roughly 100 miles southeast of the Hudson. The canyon got little study until 2002 when Rona, the US Geological Survey, the Woods Hole Oceanographic Institution and the federal oceans agency teamed for a voyage of exploration.

The NOAA ship, Ron Brown, used sound to chart the canyon’s recesses in great detail. With this first map in hand, scientists turned to the question of what made the canyon such a biological hotspot, as well as whether its nooks and crannies might harbour some of nature’s more exotic creatures and ecosystems.

“We have a mandate to protect delicate habitats,” said Vincent G Guida, a biologist at the NOAA Northeast Fisheries Science Center who led later expeditions with Rona. In 2007, the scientists deployed a free-swimming robot that mapped the canyon’s head in greater detail. It came from the National Institute for Undersea Science and Technology, a joint venture of NOAA and the University of Mississippi. In 2008, the scientists discovered high levels of methane in the water and confirmed that finding in 2009.

The maps made last year revealed the icy seabed to be riddled with giant pits. Rona said such features are well known, with geologists linking them to the shrinkage and collapse of methane ice, known as methane hydrates. “We found whole families of these things,” he said.

The seabed pits ranged from the size of Ping-Pong tables to giant craters almost a half mile across. In December, Rona, Guida and 10 other scientists presented their Hudson Canyon findings to the annual fall meeting of the American Geophysical Union. Mary Scranton of Stony Brook University did the methane analysis.

A new robot to be deployed
Next month, the scientists plan to deploy into the sunless depths a new kind of robot from the National Institute for Undersea Science and Technology. The robot’s lights and cameras – both still and video – promise to illuminate the wilderness, revealing much. The discovery of dark ecosystems, Rona said, would suggest new rounds of research seeking to understand the role of chemosynthetic habitats in maintaining the canyon’s overall vitality.

“There could be systems of organisms that go up the food chain,” as in the Gulf of Mexico, he said.

Rona added that the canyon probably held more surprises. “It’s right at the doorstep of metropolitan New York,” he said. “But it’s largely unexplored.”

New York Times News Service