Coral in Singapore's reefs releasing egg-sperm bundles in 2010. The bundles will break up upon reaching the surface of the sea to allow fertilisation to occur. A new round of coral spawning is expected this weekend.
SINGAPORE - Singapore may be tiny, but it is home to one-third of the world's coral species.
However, it has lost 60 per cent of its original reefs, especially deeper ones, to development and silt kicked up by reclamation.
When these threats clash with the need to conserve natural habitats, artificial reefs can be a potential solution.
Industrial developer JTC Corporation (once the Jurong Town Corporation) is planning a small pilot test of an artificial reef at the north-west corner of Sisters' Island in Singapore's southern waters.
Last month, it called a tender for experts to work out the environmental impact of the proposed pilot reef and the details of a coral transplantation programme. The tender closes on April 22.
Among the factors to be studied: the quality of the water at the site; the amount of sediment the site gets; whether sediments contain heavy metals and chemicals toxic to marine life; the shape and slope of the sea floor; whether it will affect other corals growing naturally nearby; and whether it will have any impact on ships' safe navigation, among other things.
If the artificial reef project is feasible, the next step will be to transplant corals onto a prism-shaped structure made of granite rocks.
A JTC spokesman told The Sunday Times that the project was a follow- up from a theoretical study two years ago that identified Sisters' Island as a possible trial site for an artificial reef.
And depending on its success, further studies can be conducted to select additional sites if required in the future.
She said: "When planning for possible future coastal development plans, one of the factors that JTC takes into account is the coral reef habitat.
"As some developments might potentially cause impact to the corals, one possible pre-emptive mitigation measure is to create artificial reefs to house affected coral habitats. This will help to safeguard Singapore's coral reef biodiversity."
But the JTC effort is not the first of its kind here. Over the years, at least three artificial reef projects were set up for various purposes, but they have had mixed results.
Why would anyone build an artificial reef? Initially, they were used in Japan and the United States to attract fish to commercial and recreational fisheries, said National University of Singapore marine biology expert Chou Loke Ming.
In some countries, they are used for dive tourism. Shepherding divers to a sunken car or underwater statue garden helps take pressure off other reef sites.
And in Indonesia's Komodo National Park, piles of granite rocks were used as a cheap, readily-available base for corals to grow back after dynamite fishing damaged existing reefs.
The latter project was the inspiration for JTC's reef design, said Dr Karenne Tun, deputy director of the coastal and marine department at the National Parks Board's National Biodiversity Centre.
In 1989, Professor Chou and fellow researchers sank the first artificial reefs in Singapore - 20m deep - off the island of Pulau Busing, near Pulau Hantu. Then, they were made from tyres roped together, and hollow concrete blocks. Rather than growing corals, they attracted fish, barnacles and other wildlife.
But the ropes holding the tyres together frayed and degraded after years in the ocean, and the tyre piles fell apart.
In 2005, Prof Chou and colleagues put small fibreglass domes at two Southern Islands to see if they could serve as artificial reefs for coral to grow. Two years on, some had washed away as they were not anchored well, but others had dug in and were covered with corals and other reef life.
About six years ago, a team from the Singapore Maritime Academy at Singapore Polytechnic placed structures made of concrete and PVC pipes off Labrador Park, and transplanted corals onto them.
Some of the corals have survived. But Mr Charles Rowe, 64, a commercial diving supervisor who led the project with Maritime Academy lecturer Captain Frederick Francis, said he wished it had received more scientific help from the start.
Said Dr Tun: "Having a comprehensive matrix to select your site is really the precursor to whether the project will succeed."
Factors to look at include determining whether the surface is stable, the water quality is suitable, and if it's shallow enough for corals to get enough light.
She said the Sisters' Island site, with its strong currents, could serve as a good "seed reef" from which coral larvae could be spread all through Singapore's waters.
After some coral species spawn, their eggs and sperm join to form free-floating larvae, which - if they survive - can settle and transform into polyps and form colonies that make up a reef.
Others grow when polyps bud off to form new colonies, or when fragments from a parent structure fall off, say, during a storm.
And Singapore's corals are still spawning, with the next round expected to start this weekend.
There is no difference to coral growth whether the reef is a man-made structure or a bleached, barren piece of rock recovering from damage, Dr Tun added.
"If it's a suitable place, coral larvae will settle and they will grow," she said.
But it takes five to 10 years of monitoring to make sure artificial reef projects thrive, noted Prof Chou.
One of his students is now checking on the success of the fibreglass domes placed almost 10 years ago. "To be out of the woods requires decades," he said.