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Undersea mountains yield living 'fossils'
Between the devil and the deep blue Coral and Tasman seas bordering New Caledonia and Tasmania, scientists have discovered hundreds of new species on extinct underwater volcanoes rising from the sea floor.
Some are living "fossils" from groups believed extinct since the Mesozoic period, the time of the dinosaurs.
"Creatures have been marooned on their underwater peaks for millions of years," says Tony Koslow, a marine researcher at CSIRO, Australia's national science agency. "The seamounts are virtual islands in the deep ocean."
A report on the discoveries is published in the June 22 issue of the journal Nature.
Koslow, one of the authors of the study, says the findings have dramatic implications for the conservation of these unique deep-sea ecosystems.
Evolution has taken a widely divergent path on seamounts, which are submarine mountain ranges formed by volcanic activity. Different species have evolved independently in each area, the researchers note.
"Seamounts are increasingly being targeted by international deep-water trawling operations," says Koslow. "The spread of trawl fisheries for orange roughy, alfonsino and other deepwater fish threatens seamount communities worldwide.
"We need to consider a regional approach between nations of the western Pacific to ensure the survival of seamount communities."
Koslow says there are about 30,000 seamounts in the world's oceans, but most species previously known from this deep ocean environment come from sampling only five of the extinct volcanoes.
The unique biological communities on seamounts are dominated by corals adapted to life in the deep sea, as well as sponges, sea fans and other organisms that filter their prey from the strong currents characteristic of this environment.
Based on a sample of less than 25 seamounts in the Tasman and Coral Sea region, the study uncovered more than 850 species, 42% more than previously reported from all studies of seamounts in the past 125 years.
Koslow says about one-third of these species are new to science and are likely to be restricted to the seamount environment.
"Most importantly, we also found very little overlap in the species occurring on seamounts between one ridge system and another, even those at the same latitude and separated by as little as 1,000 kilometers (625 miles)," Koslow says.
"We found not a single species in common between the seamounts off Tasmania and those 3,000 kilometers (1,875 miles) to the north, which is extremely unusual for the deep sea, where most species have extremely wide distributions, typically over much of an ocean basin."
The authors of the study Koslow, Bertrand Richer de Forges from Centre IRD de Noumea and Gary Poore from the Museum of Victoria emphasize the conservation implications of their findings.
"This past year deepwater trawling for the first time extended from the Atlantic and Pacific oceans to previously unfished seamounts on the high seas in the Indian Ocean," says Koslow. "Our findings show that seamounts require localised protection and that this protection must cover both areas within the Exclusive Economic Zone of coastal nations and on the high seas."
Poore says seamount communities were extremely vulnerable to the impact of fishing. "The extreme age, often over 100 years, for many of these species, their fixed habitat and the limited exchange between seamounts all compound the uncertainty of recovery from trawling," he says.
In 1999, with the support of the fishing industry, Australia established a unique protected area for a group of seamounts south of Tasmania.
"What is needed is regional conservation based on a collaborative program of research between Australia, France and New Zealand," Richer de Forges says. "The southwest Pacific contains the greatest density of seamounts and seamount ridge systems in the world. Its conservation needs to be undertaken jointly."
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