Singapore's waters have been home to some 255 species of reef-building hard coral, but researchers have seen fewer of them in recent years.
National University of Singapore marine biologist Huang Danwei, in a study led by recently retired coral expert Chou Loke Ming, said he has recorded only 170 species since 2005.
Species such as the Seriatopora hystrix (thin bird's nest coral) and the Echinopora horrida (hedgehog coral), for instance, can no longer be seen in local waters.
This is not surprising, given the loss of habitat areas that Singapore has experienced, said Dr Huang.
"I think we're lucky that we have lost only at most 85 of our historically recorded 255 species."
Over the past 30 years, Singapore has also lost about 65 per cent of its original coral reefs due to reclamation work.
Unlike projects today, those in charge of earlier works did not take precautions, such as having barriers around the site to contain the sediment spread.
When the seabed is stirred up by reclamation, particles become suspended in the water and are abrasive against the soft tissue of the corals.
Reclamation also affects visibility, meaning less sunlight passes through the water and less algae grow on the corals.
Since corals depend largely on algae for food, many slowly died.
As a result of the sedimentation, Singapore's remaining reefs cannot grow at depths beyond 8m. Up until the mid-1960s, corals and other reef life used to thrive at depths of more than 10m.
Still, Dr Huang believes the local extinction is reversible.
"Our coral populations are genetically well connected to others in the region, such as those in Malaysia and Indonesia," he said.
"If we can find a way to reduce sedimentation levels and impacts from shipping and recreation, there is a high chance that these 85 species can find their way back and thrive in our waters."
This article was first published on Jan 25, 2015.
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