Among sea's big surprises? Meat-eating sponges

An ongoing census of ocean life tallies 40,000 species, rich diversity.

By , Staff writer of The Christian Science Monitor

Tracey Sutton is not your typical census taker.

Instead of pounding the pavement seeking heads of household, he combs museum collections and spends weeks cruising the ocean to learn what thrives in the deep.

His efforts are part of a 10-year project to complete the first census of marine life. Wednesday, project officials provided a midway tally of their findings so far - more than 40,000 species identified, many new to science, and a surprising amount of diversity in regions once thought to be bereft of much sea life.

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They've discovered, for instance, meat-eating sea sponges, and they've tracked a blue-fin tuna as it crossed the Pacific three times in less than two years.

The aim of the 73-nation project reaches far beyond cataloging the new and unusual. Ultimately, the results are expected to help humans manage marine resources in a sustainable way, researchers say.

"One of the best products from the census so far is the information that allows us to ask better questions," says Dr. Sutton, a researcher at the Harbor Branch Oceanographic Institution in Fort Pierce, Fla. "We've started to go from 'what's here?' to 'why is it here and how much does it vary?' " Answers to those questions, he says, "are what we need to protect the ocean."

The census grew out of a 1995 report from the National Academies of Science describing a startling level of ignorance about ocean biodiversity, notes Ron O'Dor, the project's chief scientist. The deep-sea floor covers nearly 116 million square miles at an average depth of 2.5 miles. The area the census has sampled so far would cover only a handful of football fields.

In gathering their data, scientists are focusing on biological hot spots and sampling those, Sutton says. That directs their focus to coastlines, continental shelves, and undersea features such as submerged mountains or mid-ocean ridges, where the earth's crust is being renewed.

Sutton's census-taking neighborhood lies along the mid-Atlantic ridge, a zipper-like line of mountains and crosscutting valleys that runs the length of the Atlantic Ocean. Tallying life along the ridge involves 115 scientists from 14 countries. The ridge supports an abundance of life that turns the waters above it into a refueling stop for whales, sharks, tuna, and migratory fish that live closer to the surface, he says.

The team's vessel uses high-resolution sonar to spot fish more than a mile below the surface, then rolls out large nets. The nets, designed to close at different depths, allow the team to sample waters at various levels within their broad zone of interest.

One two-month cruise this year garnered 300 species. Of those, the team found four to six "real good candidates for new species," Sutton says.

"Things look weird when you get that deep," he adds. At those depths, many fish look like refugees from a B horror movie. Some are snakelike, sporting large heads with sharp, curved teeth. Many dangle luminescent lures to draw prey. Others light up to attract mates or startle predators. All are extremely fragile. With nothing more solid than one another to bump into, these creatures die when coming into contact with the nets. Their fragility also makes tagging them impossible, although researchers are working on ways to do that.

Another census-related project is under way along the Pacific Coast of the Northwest, where scientists are implanting tiny sonar devices in young salmon. Each salmon's tag carries a serial number. Sensors on the continental shelf track the fish as they travel out into the ocean and back to their freshwater spawning grounds.

"We've been operating in more of an ocean-observing system mode," says David Welch, chief scientist for this aspect of the census. The salmon-tracking system is expected to reveal how salmon travel patterns change with changes in the water's density, temperature, and salinity. The data could be crucial to managing salmon fisheries, he says.

Though results so far aren't enough to allow researchers to create a meaningful picture of the whole ocean, planners expect that to change in the next five years.

"New technologies are revealing new aspects of marine ecosystems," says Fred Grassle, who heads the project's scientific steering committee. New sonar, satellite tagging, DNA "bar-coding" to identify species, and the establishment of a common database "will give us a real census we can use" by 2010, he says.

The need for some way to assess what humans are doing to the world's marine life is important, adds Joshua Reichert, director of the environment program at the Pew Charitable Trusts. "Take white tipped sharks in the Gulf of Mexico. Estimates are that 98 percent are gone, and they are a top predator. This large-scale removal is likely to have profound consequences."

Learning more about the habits and ecological needs of such creatures is useful, but if people focus on that kind of information "you lose the picture that we're essentially driving them into ecological extinction," he says. "That's the story that should be told and doesn't get told. That's the challenge in front of us, and we have a very short time to meet it."

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