Coral spawning muted in Republic after 2024 mass bleaching event

Singapore's coral reefs had a muted reproductive season in 2025, not because of any oil spill that occurred in the last year, but most likely because of mass coral bleaching in 2024, one of the hottest years on record.

- Shabana Begum

Coral spawning was observed in April at Pulau Satumu — where Raffles Lighthouse is located — but the National Parks Board (NParks) and scientists from the National University of Singapore (NUS) said it was more muted than in previous years.

Mass spawning events occur once a year, a spectacular underwater show in which the coral reefs appear to "snow", as they release bundles of coral eggs and sperm. The phenomenon usually happens a few nights after the full moon following the spring equinox.

The eggs and sperm then join to form larvae, which are carried by the water until some find a hard surface on which to latch on and grow.

The 2025 spawning event occurred between April 15 and 19. Corals that had recovered from the bleaching in 2024 may not have had enough energy to reproduce this time, said NParks and NUS in a joint response to The Straits Times.

NParks conducts annual coral spawning surveys, along with researchers from NUS' Tropical Marine Science Institute (TMSI) and St John's Island National Marine Laboratory.

While scientists are still analysing how much more subdued this reproductive event is compared with previous years, the scale of the event was similar to the spawning in 2017, which occurred months after the 2016 mass bleaching event.