The challenge of the Census of Marine Life: count all the forms of life in the oceans in a decade. Now in its fourth year, the rate of discovery of new species is far from slowing, even in waters that have already been studied extensively. Frederick Grassle from Rutgers' Institute of Marine and Costal Sciences believes they're just skimming the surface so far.

According to the New Scientist:

Studies are locating close to 50 new marine species every week, of which typically only two or three are fish. But the majority of unknown species may turn out to be tiny algae floating in the ocean and nematode worms on the sea bed, say the researchers.

The database recording the distributuion of species, the Ocean Biogeographic Information System, shows more than 38,000 species, including about 15,500 fish. Reporting on a press conference earlier this week, the NYT explains:

The census is actually a network of research projects in more than 70 countries. Database records come from many sources, involving both current research and historical data from projects like one that has been monitoring plankton growth in the North Atlantic and North Sea for more than 70 years.

The 40,000 species cataloged so far represent less than one-fifth of the number of described marine species. And most scientists believe there are many more remaining to be discovered, particularly in the deep oceans.

From the Nouvel Observateur, according to Grassle only 5% of the oceans have been explored, and 95% of the data studied by the Census deals with only the zone closest to the surface. Less than 0.1% is from the bottom half of the water column in the ocean deeps. That's where the odds are greatest for discovering new species. Another major challenge is size of the organisms: more than 90% of marine life is composed of microorganisms.

The reporters covering the press conference clearly had some personal favorites among the discoveries and surprises described by the scientists overseeing the project. The NYT includes:

a gold-speckled and red-striped goby fish, found in Guam's waters, that somehow lives in partnership with a snapping shrimp at its tail. While the goby stands sentinel, the shrimps digs a burrow that both use for shelter.

Another surprise for biologists was a colony of rhodoliths, a coral-like marine algae, found in Prince William Sound in Alaska. The hard, red plants, which resemble toy jacks, roll like tumbleweeds in the beds used as nurseries by shrimp and scallops.

The New Scientist passes along this surprise:

“My find of the year was the discovery of a lost tribe of green sturgeon,” says Ron O’Dor at Dalhousie University, Halifax, Nova Scotia, chief scientist for the census.

“This happened purely by chance,” he says: “Researchers were tagging the sturgeon in the rivers of California. We regarded them as purely river fish, but were unsure quite how far they travelled. Then we got a surprise. The tagged fish started showing up in the open ocean off Vancouver Island in Canada. That kind of thing just makes you think how little we know, even about familiar fish.”

The part of the census dealing with microbe is just beginning says the NYT.

Once that part is done, scientists believe they will find that the oceans extending across 70 percent of the earth's surface hold 20,000 species of fish and up to 1.98 million species of animals and plants, many of them small, basic life-forms like worms and jellyfish.

Studying the genomes, or genetic codes, of the species will "lead to the past history, the past evolution of life in the oceans, which goes back way before the fossil record three-and-a-half billion years,'' Grassle said.

Photo: A specimen de Narcomedusae, un sub-group of medusae, collected in the Canadian Arctic. (Kevin Raskoff, Census of Marine Life) printed in Le nouvel observateur