Coral Transplant Surgery Prescribed for Japan
Beneath the waves of this sapphire-blue corner of the East China Sea, a team of divers was busily at work.
Hovering along the steep, bony face of a dying coral reef, some divers bored holes into the hard surface with compressed-air drills that released plumes of glittering bubbles. Others followed, gently inserting small ceramic discs into the fresh openings.
Each disc carried a tiny sliver of hope for the reef, in the shape of fingertip-size sprigs of brightly colored, fledgling coral.
This undersea work site may look like a scene from a Jules Verne novel, but it is part of a government-led effort to save Japan’s largest coral reef, near the southern end of the Okinawa chain of islands. True to form in Japan, the project involves new technology, painstaking attention to detail and a generous dose of taxpayer money.
The project has drawn national attention, coming after alarming reports in the last decade that up to 90 percent of the coral that surrounds many of Okinawa’s islands has died off. This raised a rare preservationist outcry in a heavily industrialized nation whose coastal vistas tend toward concrete sea walls and oil refineries.
The result has been what marine biologists call one of the largest coral restoration projects in the world, begun four years ago. The goal, say biologists, is to perfect methods that could be used around the world to rescue reefs endangered by overfishing, pollution and global warming.
They say they are using the Sekisei Lagoon Reef, which is named after the broad, shallow lagoon that it created, as a test bed for new techniques that they hope will one day make transplanting coral in the sea as routine as raising tree saplings on land.
“We have been replanting forests for 4,000 years, but we are only just now learning how to revive a coral reef,” said Mineo Okamoto, a marine biologist at Tokyo University of Marine Science and Technology, who has led development of the palm-size ceramic discs. “We finally have the technology.”
Critics, however, say the project might be wasted effort. They say transplanting is futile without addressing the problems that caused the reefs to deteriorate in the first place, like coastal redevelopment and chemical runoff from terrestrial agriculture. There is also the bigger problem of rising ocean water temperatures, for which there may be no easy fix.
Here in the Sekisei Lagoon, which sits between the tropical islands of Ishigaki and Iriomote, another problem also becomes apparent: the puny size of the efforts to save a reef that stretches as far as the eye can see in almost every direction.
Since 2005, the project has planted around 13,000 pieces of coral, at a cost of some $2 million, said Hajime Hirosawa, a preservation officer at the Environment Ministry who helps oversee the transplanting. This is a far cry, he admits, from the tens of millions of pieces that need to be transplanted in this reef alone, which stretches over an area of about 100 square miles.
Worse, survival rates have been low, Mr. Hirosawa said. Only a third of the coral sprigs transplanted in 2005 have survived threats ranging from predators like the Crown-of-Thorns starfish to “bleaching,” an ultimately fatal condition caused when rising water temperatures turn coral a sickly white.
“Saving the reef is not something that we can do in three to four years,” Mr. Hirosawa said, “but more like 30 to 40 years.”
Still, say Mr. Hirosawa and others, the techniques have steadily improved, lifting survival rates. One change was to shift from placing new coral on flat sea bottoms, which proved vulnerable to typhoon-driven surface waves that broke off coral, to more protected vertical reef faces.
Another advance was the ceramic discs, which are baked at 2,700 degrees until hardened, but whose surface contains tiny pores that allow coral larvae to take root. Every spring, a team of a dozen divers has spent up to two weeks drilling holes and gluing in the discs.
While labor intensive, this method offers a more secure footing for the young coral than previous methods, like attaching coral pieces with wire and nails, Dr. Okamoto said.
The improved transplanting methods have become promising enough that the Environment Ministry says it plans to double the number of coral pieces planted next year, to 10,000.
While the project’s main goal is environmental, there are also geopolitical motivations. Tokyo plans a much larger and more expensive coral transplantation to try to strengthen the reef protecting Okinotori, a tiny, remote islet that Japan uses to claim economic control of a vast swath of the Pacific Ocean. The government wants to prevent a strong typhoon from wiping away the tiny outcropping, and with it the basis for Japan’s territorial claims, which have already been challenged by China.
There is also a friendly race among global scientists trying to develop the best coral transplantation method. Competing ideas vary from creating coral habitat with large concrete “reef balls” to the use of mild electric current to speed coral growth.
For now, the most common transplanting technique involves breaking off pieces of adult coral and affixing them elsewhere on the reef. Besides damaging the host coral, this method, while quick and easy, also means that most of the transplanted pieces share the host’s DNA, giving the reef a smaller and less healthy gene pool.
In the Japanese method, the discs are stacked underwater for 18 months near a healthy stretch of reef, allowing coral larvae released during spawning to naturally attach and grow on the ceramic surface. This ensures that each disc carries genetically distinct coral organisms, more closely replicating the results of natural reproduction.
“Japan’s methods are expensive and labor intensive, but they also bring more genetic diversity and thus healthy reefs,” said Baruch Rinkevich, a specialist in coral transplantation at Israel’s National Institute of Oceanography in Haifa.
In Sekisei Lagoon, healthy reefs are increasingly found only along the lagoon’s north side, where most coral still flourishes. This has led scientists to speculate that the north side may have evolved coral species adapted to surviving in warmer oceans. Starting next year, the divers will transplant northern coral to the lagoon’s more decimated southern side, said Shuichi Fujiwara, the diving team leader.
“This is absolutely worth doing,” said one of the team’s divers, Ryo Isobe, 26, who works as a diving instructor during the summer tourist season. “When I think of how colorful these reefs used to be, I know we need to do all we can.”