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Voyage reveals extraordinary life around deep-sea gas seeps |
| TheAllINeed.com |
(NC&T/SIO) "This is the first time cold seeps have been viewed and sampled in the southwest Pacific and will greatly contribute to our knowledge of these intriguing ecosystems," says Amy Baco-Taylor from the Woods Hole Oceanographic Institution (WHOI) in Massachusetts, who co-led the voyage with Ashley Rowden from New Zealand's National Institute of Water & Atmospheric Research (NIWA).
The 21-member expedition—led by scientists from WHOI, NIWA, Scripps Oceanography and the University of Hawaii at Manoa (UH)— spent two weeks onboard NIWA's deepwater research vessel Tangaroa exploring cold water seeps and other "chemosynthetic" ecosystems around New Zealand's east coast.
"The newly discovered sites provide a window into the biogeography of South Pacific chemosynthetic ecosystems," said Levin, a professor at Scripps. "New Zealand's seeps show some resemblance to those at comparable depths and latitudes off of California and Oregon, but the better oxygenated bottom waters off New Zealand appear to enhance the animal diversity."
Cold seeps are areas of the seafloor where methane gas or hydrogen sulphide escapes from large stores deep below. Like hydrothermal vents, cold seeps support unique communities of animals living in symbiosis with microbes that can convert these energy-rich chemicals to living matter (a form of "chemosynthesis") in the absence of sunlight.
 | | Marine tube worms, also known as "vestimentiferan" worms, were obtained from an area known as the "Builder's Pencil," one of the largest seep sites in the world. (Photo: NOAA/NIWA) |
New Zealand is one of the few places in the world where at least four types of chemosynthetic habitats occur in close proximity, allowing scientists to address key questions about the patterns of biological distribution that cannot be addressed elsewhere.
The team visited eight cold seep sites at depths of 750 to 1,050 meters on the continental slope to the east of the North Island.
"We discovered that one of these sites, the 'Builder's Pencil,' covers about 180,000 square meters, making it one of the largest seep sites in the world," says Rowden.
A few cold seep sites were previously known along the New Zealand coast from geological and biogeochemical studies of the continental margin. But this is the first time the biodiversity of the animal communities living at these sites has been observed directly and thoroughly documented, providing the first discovery of cold seep communities in the entire southwest Pacific.
"The nearest known cold seep communities that have been biologically described are off Chile and Japan. The seeps off New Zealand are also remarkable in the sheer extent of their chemosynthetic communities," says Baco-Taylor.
The team pinpointed potential seep sites using sophisticated sonar to map seafloor topography and substrate and to detect plumes of methane-enriched water. The scientists then lowered a towed video and still camera system over each site to identify seep organisms and the extent of the seafloor they covered.
With the live video feed, the scientists observed 30—40-centimeter-long tube worms emerging from beneath limestone boulders and slabs lying at the core of the seeps. Around the rocks were patches of blackened sediment and pockets of white bacterial mats. Most sites also had extensive shell beds consisting of live and dead shells of various types of clams and mussels. These were fringed with stands of a type of gutless deep-sea tube worm that relies on symbiotic bacteria for its nutrition. Corals and numerous sponges also were observed.
"We've collected samples of the animals living around the seeps for formal identification, but the distance to previously studied cold seeps implies that there are several species new to science among these new collections," says Rowden.
The team also has collected samples of the sediment and water surrounding the seeps for chemical analysis and used sonar to study the geological structures lying beneath them.
The discovery of so many sites suggests that cold seeps are very abundant along New Zealand's eastern continental margin. However, this expedition also revealed the extent to which these communities may face serious threats from human activities. At all of the seep sites there was evidence of fishing damage in the form of trawl marks, lost fishing gear and extensive areas of deep-sea coral rubble.
"Our cruise was an outstanding demonstration of international and interdisciplinary collaboration," said Levin. "Scientists from eight countries representing both the earth and biological sciences worked together to map, explore, observe and interpret New Zealand's seep communities for the first time. It is my hope that the simultaneous discovery of novel seep communities and extensive human impact will promote conservation efforts for these and similar habitats along the ocean margins."
This voyage was jointly funded by the U.S. National Oceanographic and Atmospheric Administration's Office of Ocean Exploration (NOAA OE) and NIWA, with additional support from WHOI, Scripps, and UH.
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| Quotes | Heres tae the fool on the hill and his pals that are down in the valley.- Wolfstone, Glass and the Can
He thought the formula for water was H-I-J-K-L-M-N-O (H-to-O).
He uses statistics as a drunken man uses lampposts — for support rather than illumination. — Andrew Lang.
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