"This suggests that the thermal history of these sites may have played an important role in determining the bleaching severity in 2010.
"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.
"The most parsimonious explanation, therefore, is that coral populations that bleached during the last major warming event in 1998 have adapted and/or acclimatised to thermal stress. This is controversial because many scientists believe that corals have exhausted their capacity to adapt to thermal stress."
While these results are encouraging, Dr Guest says, it does not necessarily mean that the global threat to reefs has lessened. There are likely to be limits to thermal adaptation and acclimatisation, and there may be other costs to the corals, such as reduced growth and reproductive health. As well, reefs continue to be threatened by overfishing, pollution, diseases and ocean acidification.
"The results of the present study do indicate, however, that the effects of coral bleaching will not be 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."
|Contact: Bob Beale|
University of New South Wales