Every year, following the November full moon, Australia’s Great Barrier Reef comes alive with the world’s largest coral spawning event. Sir David Attenborough himself described it as “one of the greatest of all natural spectacles”, and we can bet you’ve never seen anything quite like it.
During this extraordinary phenomenon, millions of eggs and sperm are released into the water at the same time, creating the biggest reproductive show on Earth. This event was first witnessed on Magnetic Island in 1982 and has been closely monitored by coral experts for the past 40 years. This year, scientists have taken their regeneration efforts to the next level with Coral IVF, a groundbreaking technique that boosts the corals’ fertilisation chances 100-fold. Here’s everything you need to know about the Great Barrier Reef’s coral spawning event.
What is coral spawning?
Coral spawning is the annual process by which coral simultaneously reproduce in the Great Barrier Reef. The coral polyps scatter millions of tiny egg and sperm bundles they’ve been amassing for months into the ocean, after which each bundle must find another bundle from the same species to fertilise. When they do, the fertilised eggs settle on the ocean floor, eventually growing into coral and breathing new life into the reef.
When is the coral spawning in the Great Barrier Reef?
This annual spawning spectacle typically happens on the outer reefs off Cairns and Port Douglas two to six nights after the November full moon. Meanwhile, inshore reefs tend to spawn a month before the outer reef. Ocean factors like temperature, salinity levels and tides also impact its onset, with water temperatures of 27-28 degrees Celsius required to trigger the maturation of the coral’s egg and sperm bundles.
The mass coral spawning only happens at night and can last anywhere from a couple of hours to several days. Different species of coral spawn on different days to prevent cross-breeding.
How to see the coral spawning in the Great Barrier Reef?
Witnessing the coral spawning spectacle is a rare and mesmerising experience, as the dispersion of polyps is only visible underwater. If you want to see the majesty of the coral life cycle, your best chance is to join a Great Barrier Reef dive boat tour departing from Cairns.
What happened during the 2024 coral spawning?
The annual spawning event is the most significant day of the year for coral scientists working to protect this natural phenomenon from the increasing threats of climate change. In an attempt to boost the number of coral babies produced in 2024, researchers from the Australian Institute of Marine Science (AIMS) are experimenting with a coral larval seeding technique known as Coral IVF.
The scientists will collect millions of coral eggs and sperm bundles, nurturing them in special nursery pools for up to a week as they develop into coral larvae. This increases their fertilisation success rates, improving the odds from one in a million to one in 10,000.
Once ready, they’ll move the coral bundles onto reefs, including areas affected by recent bleaching events, where they can grow into healthy young corals and help bring new life to the Great Barrier Reef.