Marine census still counting new life-forms

Gulf of Mexico ranks in top five regions for diversity

A 10-year, 2,700-scientist effort to find and record marine life estimates that 60 to 80 percent of sea species remain undiscovered.

A 10-year census of marine life turned up more than 1,200 new species, including this amphipod crustacean found off Elephant Island near Antarctica. C. d’Udekem d’Acoz/RBINS

The international Census of Marine Life has so far described 1,200 new species, with more on the way. And census scientists have tallied an average of 10,000 known marine species in each of 25 important ocean zones. The census was big, but the message emerging from 12 new papers in PLoS ONE: Ocean life is staggeringly bigger.

Based on the ease with which scientists are still finding new species, researchers suggest that much of the oceans’ diversity remains unknown.

“There is a lot more to do, but most of the big stuff is known,” says Ron O’Dor of Dalhousie University in Halifax, Canada, who served as senior scientist for the census.

Big stuff, however, such as species of whales or turtles or sea lions, barely amounts to a drop in the oceanic bucket. Census data indicate that crustaceans are the largest chunk of known marine creatures, including crabs, shrimp and the unsung but ecologically crucial krill.

Formal census efforts will come to an end in October 2010 when researchers unveil their final results. But a first set of papers on regional efforts appears online during the week of August 1.

In the current tally, Australian and Japanese ocean waters, each with about 33,000 species, top the list for highest diversity among the 25 regions surveyed. The Gulf of Mexico, examined before the 2010 oil spill, ranked in the top five with 15,374 species. (The other two high-scoring zones: China with 22,365 and the Mediterranean with 16,848.)

Other areas with lower totals, such as the waters off South Korea, were rich in species for their seabed area.

Census scientists also ranked the biggest threats to sea life. Overharvesting tops the list, O’Dor says, with fisheries such as cod collapsing dramatically in recent decades. Next come habitat destruction from coastal development, pollution, trawling and other human activities. Climate change presents a major challenge too, with perils of altered seawater chemistry.

The census is a historic effort that gives “the first integrated look at the diversity and distribution of life in the oceans,” says marine ecologist Daria Siciliano of Sea Web in San Francisco.  “In the wake of an oil spill in US waters that is likely the worst environmental disaster in history, I hope the public is more likely to pay attention to what happens to the oceans.”

Susan Milius is the life sciences writer, covering organismal biology and evolution, and has a special passion for plants, fungi and invertebrates. She studied biology and English literature.

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