Coral bleaching has grim repercussions on marine life

I commend the report on coral bleaching in Singapore ("Warming seas cause longest coral bleaching in S'pore"; Oct 24), and further emphasise the severity of this phenomenon.

Land reclamation leads to the destruction of coral habitats, and as 22 per cent of Singapore's land has been reclaimed from the sea (about 130 sq km), one might easily infer that despite being in the Coral Triangle, Singapore might not have a lot of remaining corals.

However, despite the damage that has been sustained by the reefs, as many as 250 different species of hard corals - a third of the world's known hard coral species - have been recorded in Singapore.

These corals sustain a good diversity of organisms, and thus far, 111 reef fish species from 30 families have been recorded.

Bleaching occurs because of warmer water temperatures which cause zooxanthellae (algae that corals depend on for oxygen) to be ejected from the corals, thus turning them white.

Bleaching does not mean the coral is dead. Corals can survive a bleaching event, but they are also under more stress and their mortality is in question. The algae are needed by the coral to survive, so if they are not reabsorbed, the coral ends up dying.

An increase in sea temperatures in Singapore of about 1 to 2 deg C in 1998 and 2010 led to coral bleaching, and 50 per cent to 90 per cent of all reef organisms here were affected.

These effects were just from three to four months of bleaching. As mentioned in the report, this year's bleaching began at the end of April and is still ongoing as we enter November.

This has some grim repercussions on marine life in Singapore's waters.

Shubhankar Prakash

A version of this article appeared in the print edition of The Straits Times on November 01, 2016, with the headline 'Coral bleaching has grim repercussions on marine life'. Subscribe