Slimy, green and unsightly, seaweed and algae are among the humblest of plants.
A group of scientists at a climate conference in Bali say they could also be a potent weapon against global warming, capable of sucking damaging carbon dioxide out of the atmosphere at rates comparable to the mightiest rain forests.
"The ocean's role is neglected because we can't see the vegetation," said Chung Ik-kyo, a South Korean environmental scientist. "But under the sea, there is a lot of seaweed and sea grass that can take up carbon dioxide."
The seaweed research, backed by scientists in 12 Asian-Pacific countries, is part of a broad effort to calculate how much carbon is being absorbed from the atmosphere by plants, and to increase that through reforestation and other steps.
Such so-called "carbon sinks" are considered essential to controlling greenhouse gases, which trap heat in the atmosphere and are blamed for global warming.
The conference in Bali is aimed at launching two-year negotiations for a new global warming pact to replace the Kyoto Protocol when it expires in 2012, and a major topic of discussion is the use of Earth's natural resources to remove carbon from the air.
While most of the attention to carbon sinks has been on forests, the seaweed scientists say the world should look to the oceans, where some 8 million tons of seaweed and algae are harvested from wild or cultivated sources every year.
That solution is a largely Asian one — and it's not without complications. Critics say a challenge will be keeping the carbon, once absorbed, from re-entering the atmosphere. And it's unclear how a vast increase in seaweed production would affect navigation or fisheries.
China is by far the world's largest producer of seaweed, followed by South Korea and Japan. The Asia-Pacific seas, where seaweed is used in soups, sushi and salads, accounts for 80 percent of global production.
Proponents say seaweed and algae's rapid rate of photosynthesis, the process of turning carbon dioxide and sunlight into energy and oxygen, make it a prime candidate for absorbing carbon out of the environment.
Some types of seaweed can grow 9 to 12 feet long in only three months. Lee Jae-young, with South Korea's fisheries ministry, said some seaweeds can absorb five times more carbon dioxide than plants on land. The oceans account for 50 percent of all the photosynthesis on the earth, said John Beardall, with Australia's Monash University.
"These are very productive ecosystems. They're drawing down a lot of carbon," Beardall said.
South Korea and Japan are leaders in the research. Seoul last year approved a $1.5 million a year project to investigate the possibilities. The Japanese government and a group of companies are also looking into setting up a huge cultivation area in the waters off the country's west coast.
In a presentation on the sidelines of the Bali conference on Friday, Beardall argued more efficient cultivation methods could greatly boost production in nations with long coastlines.
While the group is not recommending a specific target for expansion of seaweed cultivation, Beardall estimated that the Philippines could conceivably increase its annual output by more than 100 times with more intensive production techniques.
In addition to storing carbon, seaweed would need to be used to produce clean-burning biofuels, thereby ensuring the carbon dioxide isn't simply recycled back into the air as it would be if the seaweed is eaten.
Difference with trees
The concept, however, has problems. Skeptics say trees are effective for carbon storage because they live for many years, while seaweed is cultivated and harvested in cycles of only months, meaning the storage will be hard to measure or control.
"It depends on how long you keep the materials," said I Nyoman Suryadiputra, of Wetlands International. "Because if it is decomposed in a month, the carbon dioxide will go back into the atmosphere."
Other obstacles remain. Some critics wonder if removing water from the seaweed as it's converted to fuel would require a large amount of energy, thereby reducing the environmental benefits. Supporters say sun-drying is an option, but it could be difficult to apply that on an industrial scale.
The environmental impact of rapid expansion of seaweed farms has also not been thought out, scientists concede. Huge floating farms could complicate fishing, shipping and other maritime activities.
Chung acknowledged the idea was in its infancy.
"In terms of ball games, we are just in the bullpen," he said, "not the main game yet."