More than 700 previously unknown species have been discovered in depths of the Antarctic's Southern Ocean, including this Cylindrarcturus crustacean.
Credit: Wiebke Brokeland/German Centre for Marine Biodiversity
SYDNEY: The lightless depths of the Antarctic's Southern Ocean harbour an unexpectedly diverse "treasure trove" of marine life, including more than 700 previously unknown species, according to a new international study.
"The Antarctic deep sea is potentially the cradle of life of the global marine species," said Angelika Brandt of the Zoological Museum at the University of Hamburg, Germany, who led the study. "What was once thought to be a featureless abyss is in fact a dynamic, variable and biologically rich environment," added Katrin Linse, a marine biologist from British Antarctic Survey.
Life in abundance
A series of expeditions over three years collected samples of fauna living up to six kilometres below the surface of the Weddell Sea in the Southern Ocean – a region thought to supply much of the deep water circulating in the world's oceans.
Most of the new life forms discovered were isopods, a vast order of crustaceans ranging in size from microscopic to nearly 30 cm long. Of the 674 species cataloged, more than 80 per cent had never been previously identified.
The expeditions also turned up 160 species of snail-like gastropods and bivalves, along with 76 types of sponges, 17 of them new to science. One of these was an unusual type of carnivorous sponge – the first of its kind to be found in the deep Southern Ocean.
These findings challenge the widespread view that deep oceans are less biodiverse than shallow regions, and that polar oceans are less biologically rich than those in tropical regions.
Deep ocean nomads
In addition to the surprising variety of life, the researchers found that some organisms were astonishingly mobile. Over evolutionary timescales, species had migrated between oceanic levels, or even between oceans, revealing the importance of the Southern Ocean to cultivating marine life worldwide.
"Some of the species found in the deep Antarctic, such as the shell-bearing protozoans, Formanifera, were genetically identical to species that occur in the deep Arctic - 17,000 km away," said Andrew Gooday, a marine ecologist from the National Oceanography Centre, University of Southampton, England, and co-author of the paper.
"Other groups, such as highly adaptable crustaceans, the isopods, found on the continental slope, seem to consist of species which have migrated down from the continental shelf and up from the abyss," Gooday added. This occurs as a result of natural climate change, which causes movement of the ice shelf, making new habitats available for marine organisms.
Gooday admits that the mystery lies in explaining why this apparently uniform environment is so biologically rich. "We need to understand the biodiversity of these remote, fragile and very species-rich ecosystems before they are subjected to environmental impacts," he said.
Adele Pile, a biologist from the University of Sydney, Australia, agrees. She points out that about 60 per cent of the Earth is covered by at least a kilometre of water, and only five per cent of that has been explored. "Basically two-thirds of the planet is unexplored. We think that the final frontier is space; the first frontier is still trying to understand the life on our planet."
The inventory of deep-sea life, which is published today in the British journal Nature is the first of its kind undertaken in the Antarctic region. It was conducted as part of the ANDEEP (Antarctic Benthic Deep-Sea Biodiversity) project.
with AFP
