Census of Marine Life reveals extent of ocean mystery.

From New Scientist:

The first global picture of life in the oceans is released today, with the completion of the decade-long Census of Marine Life.

But despite its 2700 scientists spending over 9000 days at sea, the Census has only scratched the surface of the ocean's biodiversity. In all, some 250,000 marine plant and animal species have now been formally described, out of the 1 million thought to exist. "There are three to four unknown species for every known," says Paul Snelgrove of Memorial University of Newfoundland in St John's, Canada.

The Census has so far added 1200 new species to the tally, though that is likely to rise as over 5000 more organisms that were collected have yet to be studied or named. The new species include several that were thought to have disappeared, such as the "Jurassic shrimp", which was believed to have died out 50 million years ago.

The Census was also able to identify those regions that are richest in diversity, which include the Gulf of Mexico and the Australian coastline. The Galapagos Islands, meanwhile, turned out to have less biodiversity than the chilly South Orkney Islands, in the Southern Ocean near Antarctica.

However, plant and animal diversity looks insignificant compared to the sea's micro-organisms, which may number 1 billion. Their diversity is "spectacular", Snelgrove says.

The Census also assessed threats to marine life. "Fishing and exploitation is the single biggest problem," says Ron O'Dor, one of the Census's senior scientists based at The Consortium for Ocean Leadership in Washington DC. Despite its incompleteness, O'Dor says the Census will be essential for conservation efforts because it provides a baseline standard for diversity in the oceans.