Climate change hurts coral sex life

tvnz.co.nz 10 Jul 08;

Climate change could be confusing coral about when to have `sex'.

Researchers have recently discovered that the marine organisms spawn almost around the world at the same time in what experts say may be the world's biggest orgasm.

But experts believe global warming could leave corals confused, leading them to spawn at different times and in different places.

This cuts their fertilisation and lowers the replenishment rates for the fragile species, according to coral scientists meeting this week at the International Coral Research Symposium (ICRS) in Fort Lauderdale, Florida.

Co-chairing the conference session on coral reproduction is Dr Andrew Baird of the ARC Centre of Excellence for Coral Reef Studies at James Cook University in Townsville.

Dr Baird said it was previously thought that mass spawning events in coral were mainly confined to a few major reef systems, such as Australia's Great Barrier Reef and Ningaloo Reef.

"However, new research is revealing these mass spawning events occur throughout the Indo-Pacific, from French Polynesia to the Red Sea, wherever there are large numbers of coral species present, and even to a degree in the Caribbean," he said.

But global warming is putting the mass release of coral eggs and sperm under threat, said the session's co-chair Dr James Guest of the University of Newcastle.

"We're still in the process of working out exactly what the cues are which prompt many different coral species to spawn together, on the same night," Guest said.

"But it is clear that water temperature is a significant factor and under climate change that is likely to change.

"This raises the risk that corals will become confused under climate change, start spawning all over the place at different times, reducing fertilisation success and leading to less effective replenishment of coral populations."

If the corals fail to regenerate properly, as has been the case in the Caribbean, they become less able to withstand human impacts such as over fishing and pollution or climatic impacts such as hurricanes or bleaching.

The scientists say there were many factors, including moonlight-sensing genes, solar radiation, tides and possibly other seasonal cues such as the length of days, which prompt corals to spawn en masse, particularly the Acropora and favid varieties.