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| Coral reefs may be better able to withstand the expected sea temperature rises. |
A team of international scientists working in the central Pacific have discovered that coral which has survived heat stress in the past is more likely to survive it in the future.
The findings, published in the journal PLoS ONE, will help scientists identify habitats and areas where reefs may persist in the face of climate change.
The report will be welcomed by some of the millions of people worldwide who rely on coral reefs for sustenance and their livelihoods, particularly those in the fishing and tourism industries.
When water temperatures get too hot, tiny algae that provide coral its colour and major source of food is expelled. This phenomenon, called coral bleaching, can lead to the death of corals.
With tropical sea temperatures forecast to rise by between one and three degrees Celsius by the end of this century, it had been feared that all corals may be at risk of bleaching and death.
But what this study shows is that in locations where heat stress is naturally more common, coral reefs may be better able to withstand the expected sea temperature rises.
This conclusion was reached after research on the remote Central Equatorial Pacific island nation of Kiribati – an ideal natural laboratory for testing theories about past climate experience.
Corals on the equatorial islands are pounded by El Niño-driven heat waves, while corals on the islands farther from the equator are less affected.
The researchers analysed coral skeletal growth rates and tissue fat stores to compare how corals from different regions responded to two recent coral bleaching events in 2004 and 2009.
The paper is a culmination of work by The Australian Nuclear Science and Technology Organisation (ANSTO), University of British Columbia, and Scripps Institution of Oceanography.
Dr Jessica Carilli is a Post Doctoral Fellow in ANSTO’s Institute for Environmental Research and played a lead role in the research.
“Up until recently, it was widely assumed that as the oceans warm due to climate change, coral will bleach and die off worldwide,” Dr Carilli said.
“This would have very serious consequences, as loss of live coral – already observed in parts of the world - directly reduces fish habitats and the shoreline protection reefs provide from storms.
“The research findings give hope that even though warming of the oceans is already occurring, coral that has previously withstood anomalously warm water events may do so again.
“While there is certainly more research needed, this appears to be good news for the future of coral reefs in a warming climate.”
Importantly, it will also help scientists understand which areas may be more or less susceptible to bleaching in the future – assisting in the planning for future Marine Protected Areas.
Marine Protected Areas are conservation areas designed to protect marine life from stressors such as fishing. This research suggests they may be more effective in areas with naturally variable water temperatures.
According to Simon Donner, an assistant professor in the University of British Columbia’s Department of Geography and member of the research team, the study paves the way towards an important road map on the impacts of sea warming.
“We’re starting to identify the types of reef environments where corals are more likely to persist in the future,” said Donner, who has conducted field research in Kiribati since 2005.
“Kiribati is showing us that experience matters. The new data is critical for predicting the future for coral reefs, and for planning how society will cope in that future.”
The findings announced today support previous laboratory and observational studies on the Great Barrier Reef and other regions, suggesting they can be widely applied.
For Australia’s Great Barrier Reef, the research delivers mixed news because the reef stretches over such huge distances – meaning some areas have stable temperatures and some don’t.
Planning is now underway for potential future studies of coral in areas of the world that have not experienced significant historical changes in water temperatures.