14 May 2024

Mass coral spawning 2024

Singapore's corals are alive and very sexy too. Their annual orgy of explosive sex just happened! Thanks to the dedicated team who have been keeping an eye on this event every year, and Vincent Choo and Chay Hoon, we get a glimpse of what happened. Chay Hoon reported coming across 8 spawning colonies from 4 genera.
Photo by Chay Hoon.
Once a year, on the fourth month, around four days after the fourth full moon of the year, our corals seed the seas with new life! Called Mass Coral Spawning, what is it and why is it a big deal? More below!

What is Mass Coral spawning?

Some corals release their eggs and sperm all the same time. Called broadcast spawners, these mass spawning events usually occur once a year, a few nights after full moon.
Many different species of corals spawn at the same time.
Photos by Chay Hoon.
Tiny packets of eggs and sperm pop out of the coral polyps. These packets drift to the water surface where they open up, releasing the eggs and sperm for fertilization.
Photos by Chay Hoon
While bazillions of eggs and sperms are released during a mass spawn, most don't make it. Hordes of marine creatures gorge on the spawn, from fishes and crabs to jellyfishes. 
Photos by Vincent Choo
After a few days, the embryos will have developed into coral larvae that drift about and eventually settle down on a hard surface to form new corals. As the tiny coral larvae develop, they have to survive the countless predators that constantly sieve the water for plankton and edible bits. The coral larvae also have to overcome many other challenges that we are still learning about. 
A stylised depiction of the reproductive cycle of Acropora. From "Effects of sediments on the reproductive cycle of corals" R. Jonesa, G.F. Ricardoa, A.P. Negria, 2015 on ScienceDirect
Excessive sedimentation, for example, can interfere with fertilisation and other aspects of coral larvae survival and successful settlement. Coral bleaching also affects the health of the parent corals. Singapore's corals are expected to face the fourth Global Mass Coral Bleaching event in the months ahead. Let's hope they can survive to spawn again next year.
Some bleaching observed by Vincent Choo
during the spawning survey.

Why is mass coral spawning in Singapore a big deal?
From Sex in the Tropics 2008 on the blooooooooooo blog

Coral mass spawning in Singapore was first recorded by Dr James Guest in 2002. It was the first record of coral spawning in the tropics. At least 18 different coral species from ten genera and five families (Acroporidae, Faviidae, Merulinidae, Oculinidae and Pectiniidae) have been observed to spawn in our waters! Mass spawning occurs on the third to fifth nights after the full moon between 8 and 10 p.m.

In interviews with the media, Dr James Guest emphasised that corals are part of Singapore's biodiversity and natural heritage. "There are 255 species of corals recorded here, and there may be some corals here that were around before Stamford Raffles arrived."

The fact that our corals mass spawn shows that our reefs are functioning well! According to Dr James, the number of coral species in Singapore that mass spawn is "as high as on other Indo-Pacific reefs, like the Great Barrier Reef... " This shows how rich Singapore's natural heritage is. We can find right at our doorstep: "diverse, functional and fascinating coral reefs, that people would normally associate only with countries like Australia."

MORE photos of Mass Coral Spawning in 2024

Chay Hoon

Vincent Choo

Previous posts about previous coral spawning


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