'Tis the season for coral spawning

By Chang Ai-Lien
SCIENCE CORRESPONDENT

LAST week's combination of full moon and warm sea currents proved to be potent factors, resulting in Singapore waters coming alive with millions of tiny egg and sperm parcels.

One of the very few, Mr Guest caught the coral birth on camera. He gauged when it would occur after three years of studyign the reefs here. --HOW HWEE YOUNG

The occasion - the corals' spawning season, an event so rarely witnessed it has never been documented before.

But this time, two researchers captured on video and in photographs those magical moments as they occurred in the waters around Raffles Lighthouse.

The spawning is a good omen for reefs here, said National University of Singapore doctoral student James Guest, who documented the event with researcher Karenne Tun of the Tropical Marine Science Institute.

'There were at least 30 species spawning,' said Mr Guest, who is doing his PhD thesis on coral reproduction. 'The fact that they're doing so indicates that the reefs here are still alive and well. They could even spread if the waters surrounding them are cleaned up a bit.'

He gauged the time that the spawning would occur after three years of studying reefs here.

He said it probably happened simultaneously at other reefs here and around the region, as different species of coral in the same region tend to spawn at the same time, after months of gestation.

The mass event was the coral equivalent of a foam party, and filled the waters around the island with miniature pink balls of egg and sperm on three nights last week.

Each tiny parcel which is not eaten by fish and crabs floats to the water's surface, where it hopefully gets fertilised. If it is, a microscopic larva forms.

The larva settles days later on a hard surface, like a rock, metamorphosing into a sedentary coral polyp, which multiplies and forms a colony. It could take hundreds of years for a colony to grow to the size of a small car.

Only one in thousands of eggs makes it through this process.

Nearly 100,000 sq km of coral reefs - one-third of the world's total - can be found in South-east Asia, home to more than 600 of the world's 800 coral species and the global hub of marine life. Singapore has about 150 of the species.

Yet coral spawning in the region, which typically happens once a year when the moon and tides are just right, has been documented only in the Philippines and Indonesia.

Mr Guest added that since spawning happens so rarely, knowing when it will happen means that industrial activity, such as dredging, could be stopped so that the event is not disrupted.

He said: 'Many people are surprised to find out there's coral in Singapore. Though visibility in the waters here is poorer, coral life here is as good as parts of Australia's Great Barrier Reef.'