Grace Chua Straits Times 31 Mar 12;
WHAT does not kill a coral reef can make it stronger, especially when it comes to high ocean temperatures.
A team of researchers, led by scientists from the National University of Singapore (NUS), has found that some corals seem able to adapt to high temperatures that cause other corals to bleach and die.
Corals - the rich undersea habitats of fish and other marine life - are actually colonies of tiny animals called polyps, which rely on algae inside their bodies to make food from sunlight.
When they are stressed by unusually warm, polluted or acidic water, they eject these algae, which produce a ghostly white appearance. In 2010, high ocean temperatures during the El Nino weather phenomenon caused corals to bleach across the tropics, from the Philippines to Costa Rica.
But the researchers found that corals around Singapore and the Malaysian island of Tioman, which suffered and survived an earlier spate of high temperatures in 1998, were not as badly hit.
And the branching corals such as Acropora (staghorn corals) and Pocillopora (brush corals) that are typically worst-hit by warming, were not badly affected. Around Singapore, just 5 per cent of Acropora and 12 per cent of Pocillopora died.
Instead, it was the slow-growing, massive corals like Porites (finger corals) which are typically more resistant to warming, that died.
In contrast, the usual pattern was seen at Pulau Weh in Sumatra, which did not experience the 1998 warming episode. Branching corals were bleached while massive corals survived.
The team's work, led by then NUS research fellow James Guest, was published in the journal PLoS One earlier this month.
'First of all, it is important to be clear that we have not proven that adaptation has occurred in populations in Singapore,' said Dr Guest in an e-mail. He is now with the University of New South Wales.
'However, given the patterns that we saw, we suggest that adaptation is the simplest explanation.'
The next experiments, he added, are to figure out the highest temperatures such corals can withstand, how this varies among individual corals and between species, and how the type of algae in corals' cells affects their resilience.
If branching corals can adapt somewhat to climate change, there is hope yet for reefs.
But, Dr Guest said, this does not mean that the threat to reefs from climate change has lessened. Adaptation to warmer seas might still have an impact on coral growth and reproduction.
'In addition, we must build in as much 'resilience' as possible to coral reef eco-systems by managing other stressors such as fishing, pollution and sedimentation,' he added.
