The $1bn 10-year project, which is building a huge database, involves researchers in more than 70 countries.

The new knowledge will inform future conservation and fisheries policies.

"We're just skimming the surface," said Dr Ron O'Dor, Chief Census Scientist, based in Washington DC, US.

"We know something about the first 100m at this point but we know almost nothing about what lies down in the deep.

"Our analysis shows that if you catch a fish below 2,000m it is 50 times more likely to be new to science," he told the BBC News website.

Map of life

The census has seen an exponential growth in knowledge in the 12 months since it issued its last progress report.

Some specimens are pulled up on trawls, counted and catalogued. Other organisms are even tagged and tracked.

A remarkable picture of how life operates in the deep is beginning to emerge.

"In some of the results we've had you can see a kind of doughnut of circulation which seems to concentrate life in deep water," explained Dr Fred Grassle of Rutgers University, US, who chairs the Census' International Scientific Steering Committee.

"The doughnuts were 10km in diameter and thousands of metres below the surface."The project's Ocean Biographic Information System database now includes more than 5.2 million new and previously existing records of the location, date and depth at which a marine species was found - a rise of 1.1 million entries.

o create a map of the distribution of 38,000 marine species, from plankton to whales.

Vast areas of the world's oceans have yet to return any data at all.

One survey, however, on the mid-Atlantic Ridge, recorded 80,000 specimens. It is expected to add several new fish species to the 106 marked by the census this year.

Carbon storage

The current total of marine fish species now stands at 15,482. Experts expect the final count to total roughly 20,000 by the time the COML is completed in 2010.

But fish biomass is dwarfed by that of microscopic life forms. The database now includes more than 6,800 species of zooplankton, tiny animals that drift with the currents.

Microbes, the smallest organisms, astonishingly account for more than 90% of ocean biomass.

Scientists believe knowledge about this aspect of marine life will prove useful in understanding climate change, as these organisms play a crucial role in taking carbon dioxide out of the atmosphere.

"We need to know about what is there living in the deep ocean that can take up carbon and hang onto it, so that it isn't bubbling straight back out into the atmosphere again," said Dr Chris German, from the Southampton Oceanography Centre, UK.

"In that regard, I think the big discovery is that 90% of all the carbon that's taken up in life in the oceans is taken up in microbes, and a large number of those may be in the deep-ocean sediments buried beneath the sea floor," he told BBC News.