Coral bleaching in Philippine reefs:: Coincident evidences with mesoscale thermal anomalies

Massive bleaching was observed in various reefs throughout the Philippines (5-21 degreesN. 116-128 degreesE), beginning early June until late November 1998. Satellite-derived SST data from NOAA/NESDIS was used to examine thermal anomalies ('hotspots') observed in the country during this same period. Anecdotal reports from the Coral Reef Information Network of the Philippines (PhilReefs) partners revealed the extent of bleaching in other parts of the country. The observations coincided with the occurrence of a hotspot over the region. Coral community studies detected significant decrease in live coral cover (up to 46%) and increase in dead coral cover (Lip to 49%). The results support the hypothesis that elevated sea temperatures was the major cause of the bleaching event. Some patterns of susceptibility within and across reefs, possibly due to influences of factors such as wave energy, tidal fluctuations and reef morphology, were also observed. The extent and scale of the 1998 bleaching events in the Philippines could not be fully attributed to small-scale anthropogenic disturbances directly affecting reefs since severe bleaching was also observed in offshore reefs. Its coincidence with the El Nino-related temperature anomalies suggests that the interaction between human-induced and natural factors behind bleaching remains to be investigated further. This interaction is critical for reef recovery and the discrimination between both impacts can be useful for policy and decision-making processes in management.