By Richard Black
Environment Correspondent, BBC News website
A three-week voyage of discovery in the Atlantic has returned with tiny animals which appear new to science.
They include waif-like plankton with delicate translucent bodies related to jellyfish, hundreds of microscopic shrimps, and several kinds of fish.
The voyage is part of the ongoing Census of Marine Life (CoML) which aims to map ocean life throughout the world.
Plankton form the base of many marine food chains, and some populations are being disrupted by climatic change.
Zooplankton are tiny marine animals. Many live on floating plants (phytoplankton), and many are in turn eaten by fish, mammals and crustaceans.
One of the aims of the Census of Marine Zooplankton (CoMZ), part of CoML, is to provide a global inventory of these tiny organisms which will help scientists look for changes induced by climate variations or other factors.
"The deep ocean below 1,000m (3,300ft) is rarely sampled," observed Peter Wiebe, from Woods Hole Oceanographic Institution in the US, lead scientist on the recent voyage.
"It's very difficult; you need many thousands of metres of cable," he told the BBC News website. "We were able to sample at 1,000m intervals down to 5,000m (16,500 ft)."
Thousands of specimens were captured during the cruise, of which 500 have been catalogued.
They include shrimp-like copepods and ostracods, swimming worms, and tiny jellyfish - some of the gooiest and most fragile animals in the sea.
Most are adjusted to living in the cool deep, where temperatures hover around one or two Celsius.
Bringing them to the surface meant transporting them through a layer of much warmer water, around 27C.
Samples were caught in nets which could descend several kilometres
As soon as they came on board ship, they were plunged into ice-cooled buckets to restore a semblance of their usual habitat; even so, many perished before they could be studied.
This was one of the first projects to sequence DNA at sea, a process which Dr Wiebe believes will become much more common as scientists seek quick and easy ways to identify species.
"Many of these creatures occur in the Indian, Pacific and Atlantic oceans, and you can't tell them apart visually, but maybe we'll discover that genetically they are different," he said.
"If you say 'how do you sample the oceans and see what global climate change is doing?', you've got to have the background data."
Several more voyages are planned in the next two years specifically to examine zooplankton, and scientists involved in CoMZ are also finding places on other cruises in relevant areas.
By the time CoML ends in 2010, it hopes to have found and studied every zooplankton species in the ocean.