Japan's biggest coral reef artificially restored



Artificial seeding: Near the southern island of Okinawa, a baby coral grows on an artificial ceramic bead.

Credit: Tokyo University of Marine Science and Technology

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TOKYO: Scientists are in an unprecedented project to revive Japan's largest coral reef by planting thousands of baby corals growing on tiny ceramic beds.

Corals in Sekisei Lagoon stretching between the Okinawan islands of Ishigaki and Iriomote have plunged by 80 per cent over the past two decades due to rising water temperatures and damage by coral-eating starfish.

Ten-year project

"No projects in the world have ever restored a coral reef artificially... but we aim to restore the lagoon in some 10 years," said Mineo Okamoto, associate professor at the Tokyo University of Marine Science and Technology.

In a joint project with Japan's environment ministry, scientists will plant some 6,000 baby corals in the seabed in December over a 600 square-metre district.

The corals are 18 months old and grow on round ceramic beds that measure four centimetres in diameter and have single legs for planting.

It follows the implantation of 5,300 baby corals in 2006. Only one-third of them have survived, with many dying off or damaged by dead and collapsed corals stirred up in the sea by typhoons, Okamoto said.

"We have learned lessons from the previous planting regarding what are the best places to plant and other conditions for survival. We'll make a fresh try," he said.

Seafloor testbed

The attempt is the world's only large-scale project to restore a coral reef artificially, rather than trying to clean the environment for corals or nipping off branches of living corals for transplanting elsewhere, Okamoto said.

If experiments are successful, the Japanese team wants to try the method in other countries, Okamoto said, adding preparations in Indonesia have already being made.

"Corals are marine creatures but are functioning like seaweed in southern seas as they engage in photosynthesis to disperse oxygen," Okamoto noted. "They invite plankton and then plankton-feeding fish, creating an ecosystem and fishing ground," he said.