Coral That Spawns Once a Year Under a Full Moon

Quick answer: Once a year, usually after a full moon in spring, the entire Great Barrier Reef releases billions of tiny eggs and sperm at the same moment. This synchronised coral spawning turns the ocean into an underwater snowstorm and is one of nature's most spectacular events.

Hey there, Explorer! Dusty back again, still dripping wet from my adventures on the Great Barrier Reef. Boomer's staying on dry land this month, so it's just me and my flippers exploring the deep blue.

Last time I told you how big the reef is. This time I want to share something a little more magical, something most grown-ups have never even heard of. Ready? Let's get into the water.

What is coral spawning?

Here's something that sounds made up but is completely true. Once a year, the corals of the Great Barrier Reef do something remarkable. On the same night, across hundreds of kilometres, billions of corals release their eggs and sperm into the water all at once.

Scientists call this coral spawning. I call it the reef's biggest party. The water fills with tiny bundles that drift upwards like an upside-down snowfall. Divers who witness it say it looks like the ocean is filled with floating stars.

How do the corals all know when to spawn?

This is the part that truly boggles the mind. The corals do not have eyes, brains or calendars, yet they all manage to spawn within the same few nights, sometimes within the same hour.

Scientists believe the corals take their cues from three things working together: the water temperature warming in spring, the length of daylight, and the phase of the moon. The big event usually happens a few nights after a full moon, generally in late spring. Somehow, without a single word between them, billions of animals agree on the exact moment. Nature really is the cleverest explorer of all.

Why does coral spawning matter?

This once-a-year event is how the reef makes more coral. The eggs and sperm meet in the water, and new baby corals called larvae begin to form. These tiny drifters float along until they find a good spot to settle and start building. In time, they become part of the reef itself.

If you find the idea of a whole reef acting as one giant living thing fascinating, this is the fact to hold onto. Coral spawning is the reason the Great Barrier Reef keeps growing, healing and carrying on, generation after generation.

Keep exploring

And that, Explorer, is one of the ocean's best-kept secrets. A single night when the whole reef bursts into life beneath the moon. I feel very lucky to have learned about it, and even luckier to share it with you.

Next time you see a full moon, spare a thought for the corals far away in Australia, timing their great performance by that very same glow. Grab a pencil and see if you can draw what an underwater snowstorm might look like.

Keep exploring,
Dusty

Frequently asked questions

When does coral spawning happen on the Great Barrier Reef?
Coral spawning usually happens on a few nights in late spring, generally after a full moon when the water has warmed. It is an annual event.

What is coral spawning?
Coral spawning is when billions of corals release their eggs and sperm into the ocean at the same time. It is how new coral is created and how the reef keeps growing.

How do corals know when to spawn together?
Corals respond to water temperature, daylight length and the phase of the moon. These signals help billions of corals spawn within the same few nights.