“By the light of April’s full moon on Sunday or, quite likely a night or two after, corals will be mating en masse. Along the length of the island archipelago that makes up the Republic of Palau, millions of coral colonies will simultaneously release billion upon billion of eggs and sperm into the dark waters.
An hour or so after sunset, each spawning coral will discharge showers of sex cells, packaged in orange and pink blobs. They will rise to the surface in such huge numbers that they may form oily slicks metres long.
If the sea conditions are right, spawn slicks can coalesce to be large enough to be visible from space.
Once on the surface, the packages burst open, liberating eggs and sperm for fertilisation. Countless free-swimming coral larvae then develop and three or four days later, a few will have survived long enough to make it to the sea bed. There they attach to a suitable hard surface and develop into single baby coral polyps. The next generation of corals on the reefs will be launched.
A team of marine biologists from Australia, Britain and the Philippines has come to Palau to take advantage of this wonder of nature in the cause of coral reef restoration.
The scientists are here to investigate the potential of an experimental technique known as coral seeding – in other words, collecting some of the spawn from mass mating events and using it to promote the growth of new corals on reefs in need of rescue.
” (Read more)
Courier Mail, November 22nd
HERE is a chance for you to experience one of the planet’s most spellbinding natural spectacles. Within a few days, in the reefs around the Keppels, off Rockhampton and in the Capricorn Cays of the southern Great Barrier Reef, the annual spawning of coral is expected to take place.
After the bleaching of the corals in January and February in 2006, last summer’s spawning effort was half-hearted. “This year. they’re bursting to go,” said Central Queensland University coral ecologist Alison Jones. “If people can get to a reef and in the water between the 24th (tomorrow) and the 28th, about 7pm-7.30pm, they’ll have a good chance of seeing it happen.”
In a synchronised exercise, corals liberate millions of eggs on still nights, after a full moon, when the tides are not so strong, the water temperature is right, and there’s less chance of the eggs being swept away before fertilisation.
As a prelude to the spawning, reef life, little fish and shrimps become wildly agitated. Then, small pink balls can be seen bulging from the polyp mouths of the corals.
“They glow pink,” Jones explained. “Everything around the reef gets very excited and you know it will happen within half an hour.” (Read More)
I was interviewed recently by Robyn Williams for ABC’s “Science show” on the moonlight mass spawning of corals on the GBR I posted here earlier this month (“Keylight found to moonlight romance“). Click below to listen to the interview, read the transcript here or download the podcast.
“There are 400 species of corals and hundreds of invertebrates on the Great Barrier Reef. Many spawn in mass over a couple of nights after the full moon in October or November. So how do they all know to do it together? It seems that corals can detect moonlight. Ove Hoegh-Guldberg explains how a class of proteins has been discovered which tune circadian rhythms. They are produced by a particular gene. So despite the faintness of moonlight, organisms can detect it and time their spawning to maximise the chance of reproduction.
When the spawning happens, the sea is clouded with eggs and sperm. Mass spawning is a strategy to lessen the impact of predators. It may be the biggest sex event on earth. Ove Hoegh-Guldberg speculates on the origin of this mechanism.”