Signs of coral recovery here amid global bleaching event

This is as sea surface temperatures fall after marine heatwave takes toll over past months

- Chin Hui Shan

Amid the largest recorded global bleaching event, Singapore's corals are showing signs of recovery as sea surface temperatures begin to fall, with about 20 per cent to 30 per cent of them still showing signs of bleaching.

But the marine heatwave has taken its toll on some corals here, with 30 per cent to 55 per cent observed to be bleached in July, said the National Parks Board (NParks) and National University of Singapore (NUS).

This comes amid the most extensive global coral bleaching event, which saw 77 per cent of the world's coral reef areas subjected to bleaching-level heat stress, Reuters reported on Oct 18.

In mid-April, the US National Oceanic and Atmospheric Administration (NOAA) declared the global bleaching event, making it the fourth of its kind.

Global coral bleaching also took place in 1998, 2010 and 2016, and Singapore experienced mass coral bleaching then. Those years and 2024 have been El Niño years - referring to a climate phenomenon that causes sea surface temperatures in the eastern Pacific to heat up and elevate global temperatures.

Corals get their vibrant colours from microscopic algae that live in their tissues. When they get stressed from rising sea temperatures, the corals expel the algae and turn ashen white.

The first sign of mild bleaching was reported by NUS and NParks researchers in early May at Pulau Satumu and Pulau Hantu. This was around the time when sea surface temperatures were above monthly mean temperatures and annualised monthly means for extended periods, which is not normal.

In May, the sea surface temperatures around Singapore ranged between 30.84 deg C and 31.84 deg C, according to the St John's Island National Marine Laboratory's (SJINML) Marine Environment Sensing Network. The highest average monthly temperature here is usually 30.5 deg C.