Corals Survived And Adapted To Massive Bleaching Event In Southeast Asia, Study
March 12, 2012
New evidence has emerged that some coral species may be able to adapt to warmer oceans in Southeast Asian waters despite threats of global warming.
AsianScientist (Mar. 12, 2012) – New evidence has emerged that some coral species may be able to adapt to warmer oceans in Southeast Asian waters despite threats of global warming.
In the journal PLoS One, researchers have published a study on coral populations unexpectedly surviving a massive bleaching event in 2010.
For the study, the team monitored three sites in Indonesia, Singapore, and Malaysia. Corals in Indonesia’s Pulau Weh, Sumatra responded to higher sea temperatures with about 90 percent of its fast-growing branching species, such as staghorn corals, dying off in a typical reaction.
Unexpectedly in Singapore and Malaysia, colonies of fast-growing Acropora corals appeared healthy and fully pigmented, even though sea-temperature data showed that the magnitude of thermal stress was similar.
“When we looked at archived sea-surface temperature data and past bleaching records we found that the locations that had a reversed hierarchy of susceptibility and less severe bleaching in 2010 also bleached during 1998. In contrast, the site that had a normal bleaching hierarchy and severe bleaching did not bleach in 1998,” said Lead author Dr. James Guest from the University of New South Wales and Nanyang Technological University.
According to Guest, the most parsimonious explanation was that coral populations that bleached during the last major warming event in 1998 adapted and/or acclimatized to thermal stress.
Calling it a controversial hypothesis, Guest said that many scientists believe that corals have exhausted their capacity to adapt to thermal stress.
He added that the results also indicate that the effects of coral bleaching are not as uniform as previously thought and fast-growing branching taxa such as Acropora and Pocillopora are likely to persist in some locations despite increases in the frequency of thermal stress events.
Mass coral-bleaching events, caused by a breakdown in the relationship between the coral animals and their symbiotic algae, are strongly correlated with unusually high sea temperatures and have led to widespread reef degradation in recent decades.
But Guest predicts that hardier, slow-growing massive species will replace the less hardy, fast-growing branching species on reefs in future, based on a consistent trend that certain types of coral are more resistant to bleaching than others.
While these results are encouraging, there are likely to be limits to thermal adaptation and acclimatization, he said. For example, there may be other costs to corals such as reduced growth and reproductive health, and reefs also continue to be threatened by overfishing, pollution, diseases and ocean acidification.
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