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Wednesday, Sept. 27, 2000
Japanese scientists question mineral-accretion technique
By ROB GILHOOLY
A Japanese researcher who conducted a project in Okinawa to explore the effectiveness of growing reefs via mineral accretion in 1989, says he remains unsure of the effectiveness of the technique.
"From a scientific, data-collecting viewpoint, the results were good," said Dr. Kimiaki Kudo, research supervisor of the Marine Ecosystems Research Department at the Japan Marine Science and Technology Center in Kanagawa Prefecture, of the four-year experiment. "But it was impossible to say if this was due to the (mineral-accretion) method," he added.
The project was instigated by the Okinawa Prefectural Government and an Okinawa-based shipbuilding firm, who asked Kudo to look into an alternative coral-growing technology that might help Okinawa's rapidly diminishing reefs recover.
In the 12 years after Okinawa's return from U.S. military to Japanese control in 1972, studies showed that about 90 percent of Okinawa's coral reefs had been killed off by development, Kudo said.
According to a document issued by The Marine Parks Center of Japan, another contributory factor was the extensive presence of the crown-of-thorns starfish, which can destroy by predation entire coral communities.
These two factors were at the root of Kudo's experimental project, which Okinawa officials hoped might lead to a method of recovering and growing corals.
Kudo and a team of marine experts set a pyramid-shaped, three-tier structure on the seabed just off the southeast coast of Okinawa's main island.
The three tiers were fixed at 1-meter intervals onto a 6-sq.-meter concrete base. On each tier were fixed mesh sheets, onto which healthy corals from nearby reefs were transplanted.
One section was wired to take an electric current, and within a short time thick layers of limestone could be found on the structure, Kudo said.
After a year, however, the growth of coral transplanted there was not significantly greater than other areas that were not wired, Kudo said.
"An ecosystem is very complex, and there is no one factor that determines its well-being," he explained. "I saw nothing to indicate that better growth is guaranteed just by creating a clean base, such as that created by the mineral-accretion technology."
Furthermore, he argued, new limestone might act as a deterrent for growth. While transplanted adult corals will grow on virtually anything, baby coral invariably settle on objects "with a history," he said.
A number of programs in Okinawa have experimented with transplanting corals, or "coral recruitment."
Shuichi Fujiwara of the Marine Parks Center of Japan, which undertook one such research program in the early 1990s, said he believed the mineral accretion technology could prove useful in Japan, but that other tests needed to be conducted first.
"I think this may well be one way of assisting recovery, but first we have to survey the results of bleaching," he said.
The MPCJ, said Fujiwara, is just starting a study to monitor the rate of recovery in Japan after severe bleaching hit the nation's coral reefs in 1998.
According to a MPCJ report issued earlier this year, bleaching affected coastal areas from southern Okinawa to Hachijo Island south of Tokyo.
In Okinawa, some areas of the reef in the Sekisei Lagoon, which covers some 13,000 hectares between Ishigaki and Iriomote islands, had a coral mortality rate of up to 80 percent.
Yet, as in the cases of many nations around the globe that were affected in 1998, some parts of the reef remained healthy -- a factor that Fujiwara believes also deserves closer scrutiny before any "artificial" methods are considered.
"We also have to survey if there are any complications brought about by the disturbance of the environment (that may result from installing mineral-accretion structures)," Fujuwara said.
Wolf Hilbertz and Tom Goreau, the developers of the mineral-accretion technology used to restore and build coral in several places worldwide, expressed surprise that Japan had yet to make extensive experiments using the method.
"I'm baffled," said Hilbertz. "The Japanese diet is highly reliant on food from the sea and highly treasured. I would have thought the preservation of the original state of the sea would be essential."
Hisashi Kawagoe, an official at the International Coral Reef Monitoring Center in Okinawa said the use of such technology was not always appropriate.
"If the death of coral reefs was the result of human activity, then it must be humans who return them (to their original state). In a sense, it could be said that humans are at least half responsible for El Nino, but it was also largely due to natural phenomena. I think maybe it's best to leave the recovery of things affected by nature up to nature."