Biodiversity / Food / Water

August 17, 2009


New Technology Helping Restore Coral Reefs in Okinawa's Sekisei Lagoon

Keywords: Ecosystems / Biodiversity Government University / Research institute 

The Japanese Ministry of the Environment and Tokyo University's Department of Marine Science and Technology have teamed up to restore coral reefs in Sekisei Lagoon in Okinawa, using a newly developed coral regeneration method. First of all, ceramic coral settlement devices (CSDs) are stacked in frames and deployed in the ocean before the mass spawning of the corals occurs. Once coral larvae settle on the CSDs and start growing, the CSDs--with juvenile corals attached--are anchored to rocks on the seafloor.

Conventional regeneration methods are often based on asexual reproduction, in which coral fragments are harvested and then transplanted. The new method, in contrast, transplants juvenile corals that are sexually reproduced without impacting the parent coral colony. And because it takes advantage of the mass-spawning phenomenon -- in which a variety of coral species settle on the CSDs -- it preserves the genetic diversity of existing coral species. Besides this, the disc-shaped, specially designed CSDs feature an alternating concave-convex pattern that protects newly settled corals from predators. They are also lightweight and inexpensive to make, opening up the possibility of mass production of coral seedlings for transplantation, plus they allow for easier monitoring of coral growth.

Encompassing a vast coral reef area between the islands of Ishigaki-jima and Iriomote-jima, Sekisei Lagoon boasts one of Japan's best coral reef ecosystems. Unfortunately, damage to the reefs is increasing every year as sea temperature rises; the mortality rate of juvenile corals is climbing, and the population of crown-of-thorns starfish that feeds on coral is growing.

Marine scientists deployed about 60,000 CSDs in seven locations around Sekisei Lagoon in April 2008, and coral spawning was confirmed between May 18 and 20 that year. Subsequent inspection and analysis of sample CSDs, conducted August 22 to 23, indicated a recovery trend since 2005, when coral settlement rates were low.

Posted: 2009/08/17 06:00:15 AM