North West coral spawning an 'underwater snowstorm' SNOWSTORM: Dr Ray Masini peers through the haze of a spectacular coral spawning off the WA coast. Picture: Dr Chris Simpson, DEC Source: PerthNow ONE of Western Australia's most remarkable natural events - the annual coral mass spawning in the State's north west - is set to take place next week, turning the waters along our coral reefs pink. Department of Environment and Conservation (DEC) marine science program leader Dr Chris Simpson said the autumn spawning, which typically took place 7-10 nights after the March full moon, was predicted to occur between April 3-6 "Mass coral spawning looks something like a pink underwater snowstorm caused by numerous colonies of many coral species releasing their reproductive eggs at the same time," he said. It occurs during neap tides, when there is minimal tidal movement, and the colour is due to the reddish-pink hue of the buoyant coral eggs that come from the most common spawning species, Acropora sp. Most coral species are hermaphrodites with both male sperm and female eggs. Evidence suggests that synchronised nocturnal spawning occurs to maximise successful fertilisation, and it happens at night to minimise predation by plankton-eating fish. Dr Simpson said the coral spawning was a spectacular natural event that relatively few people had been lucky enough to have seen, however, it was something that the community could witness in the Dampier Archipelago, Ningaloo Marine Park and Abrolhos Islands. "The predictable nature of coral spawning, which usually goes for around two hours from about 7.30pm, makes it possible for people to experience the event by diving or using a glass-bottom bucket and a torch," he said. They might also see other species such as starfish, sea cucumbers and polychaete worms, which often spawn at the same time. Once the corals have spawned and the eggs are fertilised they develop into coral larvae over a week or so and settle on suitable reef habitat where they slowly grow into large colonies and begin the cycle all over again. Dr Simpson said that minor spawning events also occurred on the same days after the full and new moons in February and April, but the early April event would be the main period of spawning this year. Although most corals in WA spawn in autumn, a few species also spawn during spring, contrasting with the Great Barrier Reef where most corals spawn in spring/early summer.