Coral spawn a spectacular site on Qld reef

Scientists will use the Great Barrier Reef annual mass coral spawn to research how baby coral will tolerate climate change.

The soup of eggs and sperm might smell peculiar but spawning coral has pulling power.

The spectacular annual event has again attracted scientists and tourists to the Great Barrier Reef, which has lit up with the glow of colourful gametes over the past few days.

Dr Greg Torda, who has spent the spawn working 16-hour days on Orpheus Island, north of Townsville, says the event likely peaked on Monday night.

"It's one of the most spectacular natural events I've ever seen," the ARC Centre for Excellence in Coral Reef Studies post-doctorate research fellow told AAP.

"On the surface it (a gamete bundle) breaks and sperms swim away and look for eggs to fertilise."

Swimming through a spawn is regularly described as like being in a snow globe and the resulting bio matter causes slicks to be seen from the air.

The event gives researchers a rare opportunity to test the expected affects of climate change on young coral, which is especially important ahead of an expected worldwide coral bleaching event early next year.

Mr Torda thinks the "coral recruits" will have a hard start to life if water warms but says the extent of the problem can't be estimated yet.

He says scientists will attempt to monitor the survival rates of the new coral during the bleaching event.

"If it's a major event, I think we should be able to see a demographic bottleneck in this (baby coral) cohort," he said.

Corals spawn in warm waters three to six days after a full moon, meaning the event usually happens in late November or early December.

But split spawns can occur if the coral becomes confused by a full moon earlier in the month.

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