Forget the midnight dives—new research reveals that some corals, instead of the normal night spawning, are synchronising their spawning in the afternoon.
A research team of divers led by Rahul Mehrotra of Aow Thai Marine Ecology Center recorded massive daytime spawning events involving Pavona corals (commonly known as Cactus or Leaf corals) across 450km of coastline.
The 2:00 PM Snowstorm in September to December
Approximately six to eight hours after the first light of dawn touches the waves, Pavona varians begins. Pavona explanulata follows shortly after, around seven to nine hours after sunrise. This means the reef could erupt between 1:00 PM and 4:00 PM. Thousands upon thousands of tiny, pearl-like bundles rising from the colonies, drifting upwards through the sunlit water column like an inverted snowstorm of life.
This is no isolated incident. This spectacular event has been observed across more than four hundred and fifty kilometers of coastline. For these corals, it is not the absence of light that serves as the signal.
Why the Day Shift?
Most corals spawn at night to avoid hungry reef fish that would otherwise feast on the nutrient-rich eggs. So why are the Pavona corals being so bold?
The study suggests that by spawning in such massive, synchronized numbers across hundreds of miles, the corals “saturate” the predators. There are simply too many eggs for the fish to eat, ensuring enough survive to drift away and settle elsewhere. For divers, it creates a unique opportunity to witness the miracle of life in sun-drenched glory, rather than through the narrow beam of a dive torch.
It is unclear if the consistent daytime spawning of Pavona corals in the Gulf of Thailand represents a recent population-wide adaptation or a localised shift in spawning time
What This Means for Divers
The team used five years of “observation-only” SCUBA surveys—proving that recreational divers can play a massive role in citizen science without needing invasive lab equipment.
If you’re diving the Eastern Gulf of Thailand or Cambodian waters between September and December, keep your eyes peeled during those afternoon dives. The researchers noted that while Pavona was the star of the show, they also caught Cycloseris (Mushroom corals) and Porites joining the daytime party.
Source
Rahul Mehrotra et al, Coral spawning patterns in the Gulf of Thailand reveal synchronised annual daytime spawning, with a review of spawning patterns in Pavona corals across the Indo-Pacific, PLOS One, February 2026
