Evolution has taken a widely divergent path on the seamounts, with different species evolving independently in each area. Some are 'living fossils' from groups believed extinct since the Mesozoic, the time of the dinosaurs.

A report on the discoveries is published today (22 June) in the journal Nature.

"Creatures have been marooned on their underwater peaks for millions of years," says Dr Tony Koslow of CSIRO Marine Research. "The seamounts are virtual islands in the deep ocean.'

Dr Koslow, one of the authors of the report, says that the findings have dramatic implications for the conservation of these unique deep-sea ecosystems.

"Seamounts are increasingly being targeted by international deep-water trawling operations," says Dr Koslow. "The spread of trawl fisheries for orange roughy, alfonsino, and other deep-water fishes threatens seamount communities worldwide.

"It is particularly urgent, given the unique character of each seamount system and the creatures which live there.

"We need to consider a regional approach between nations of the western Pacific to ensure the survival of seamount communities."

Dr 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 these.

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.

Although based on sampling fewer 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.

A brittle star from a seamount south of Tasmania. Copyright CSIRO Australia, 2000

Dr Koslow says about a 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 1000 km," Dr Koslow says.

"We found not a single species in common between the seamounts off Tasmania and those 3000 km 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 - Dr Bertrand Richer de Forges, from Centre IRD de Noumea, Dr Gary Poore, from the Museum of Victoria, and Dr Koslow - emphasised 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 Dr 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."

Dr Poore says seamount communities were extremely vulnerable to the impacts 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, Australia established with the support of the fishing industry a unique deep ocean marine 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," Dr. 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."

TERRADAILY.COM
Equatorial Waters May Have Nurtured Life During Global Snowball
by Janet Wong
Toronto - May 25, 2000 - The precursor of modern animals may have been able to survive a Snowball Earth era that occurred some 600 million years ago because of a belt of open water along the equator, suggests scientists from the University of Toronto and Texas A&M University.