10.16.12 PALAU Bleaching study published

Research by Palau International Coral Reef Center identifies climate-change refugia

A recent study published in the scientific journal, Ecology and Evolution, by researchers from Palau International Coral Reef Center (PICRC) and their colleagues, sheds new light on how bleaching events affect coral reefs, and more importantly, how some areas in Palau appear to be naturally resistant to increased sea surface temperature.  The study entitled, “Climate-changerefugia in the sheltered bays of Palau: analog of future reefs” describes the bleaching event during the summer of 2010, when increasing temperatures around the waters of Palau were causing corals to bleach throughout the archipelago.  This study involved surveying 80 sites throughout the main Palauan Islands, identifying and measuring over 34,000 coral colonies, and assessing whether they underwent bleaching.

Climate change is one of the most pressing issues facing coral reefs in the region. Increased sea surface temperatures, associated with climate change, are expected to have serious effects on coral reefs in the Pacific Ocean.  As most marine organisms live within a narrow temperature range, even a short-term increase in temperature can have a dramatic impact on coral survival.  In the past two decades, short-term extreme high temperatures contributed to a decline of corals throughout the tropics.  With the continuing rise in atmospheric CO2, global warming leading to increased water temperatures is anticipated to get worse, which will result in greater frequency and severity of coral bleaching, a condition under which corals when stressed expel their symbiotic algae and turn white, depriving the corals of their main source of nutrients.  

The remarkable result from this research was the discovery that reefs around bays did not bleach as much as other reef habitats in Palau.  The results of the study provide important lessons for marine resource management across Micronesia.  First, there is hope for the survival of some reef areas that seem naturally resistant to higher sea surface temperatures, such as the coral reefs in the bay areas of Palau, and these resistant areas can be incorporated into the design of protected areas networks to help enhance sites that are not as resistant.  However, higher water temperatures are not the only threat to coral reefs, especially those reefs around bay areas, which, since they are in close proximity to land, are more vulnerable to land-use change than patch and outer reefs.  Therefore, protecting near-shore reefs from local disturbances may help buffer the coral reefs across the region against climate-change induced disturbances.

For more information, contact Carol Emaurois at the Palau International Coral Reef Center. Email: cemaurois@picrc.org