By Rebecca Morelle
Science reporter, BBC News
An extraordinarily diverse array of marine life has been discovered in the deep, dark waters around Antarctica.
Scientists have found more than 700 new species of marine creatures in seas once thought too hostile to sustain such rich biodiversity.
Groups of carnivorous sponges, free-swimming worms, crustaceans and molluscs were collected.
The findings, published in the journal Nature, could provide insights into the evolution of ocean life in this area.
Dr Katrin Linse, an author of the paper and a marine biologist from British Antarctic Survey (BAS), said: "What was once thought to be a featureless abyss is in fact a dynamic, variable and biologically rich environment.
"Finding this extraordinary treasure trove of marine life is our first step to understanding the complex relationships between the deep ocean and distribution of marine life."
New to science
The research formed part of the Andeep (Antarctic benthic deep-sea biodiversity) project, which is the first comprehensive study of Antarctic marine life.
It is designed to fill the "knowledge vacuum" that surrounds the fauna that inhabit the deeper parts of the Southern Ocean.
The first sampling expedition (Andeep 1) took place in 2002
Andeep 2 took also took place in 2002
Andeep 3 took place in 2005
During three research expeditions that took place between 2002 and 2005, an international team collected tens of thousands of specimens from the Weddell Sea, from depths of between 774 and 6,348m (2,539-20,826ft).
The samples were taken from diverse settings, including the continental slope, the abyssal plain and channel levees.
The researchers found the area to be teeming with lifeforms; well over 1,000 species were recovered, and many were completely new to science.
For example, they spotted 674 species of isopod (a diverse order of crustaceans), most of which had never previously been described; more than 200 polychaete species (marine worms), 81 of which were found to be new species; and 76 sponges, 17 of which had previously been unknown.
Lead author of the paper, Angelika Brandt, who is based at the Zoological Institute and Zoological Museum, University of Hamburg, Germany, said: "I initiated the Andeep project because such a vast area of the Southern Ocean had never been explored.
"We thought we might find some novel species, but previous research had suggested deep-sea diversity this far south would be poor, so we were very surprised to find such enormous diversity."
The findings could help to shed light on the evolution of ocean life in this area, Professor Brandt told the BBC News website.
By comparing the species that are found in the deep-sea and those found in the shallower waters surrounding Antarctica, scientists will be able to better understand how climate and the environment these animals live in drove past evolutionary changes.