Sea surface temperatures and coral reef bleaching off La Parguera, Puerto Rico (northeastern Caribbean Sea)

Much recent attention has been given to coral reef bleaching because of its widespread occurrence, damage to reefs, and possible connection to global change. There is still debate about the relationship between temperature an d widespread bleaching. We compared coral reef bleaching at La Parguera, Pu erto Rico to a 30-y (1966-1995) record of sea surface temperature (SST) at the same location. The last eight years of the La Parguera SST record have all had greater than average maximum temperatures; over the past 30 y maxim um summer temperature has increased 0.7 degrees C. Coral reef bleaching has been particularly frequent since the middle 1980s. The years 1969, 1987, 1 990, and 1995 were especially noteworthy for the severity of bleaching in P uerto Rico. Seven different annual temperature indices were devised to dete rmine the extent to which they could predict severe coral bleaching episode s. Three of these, maximum daily SST, days > 29.5 degrees C, and days > 30 degrees C predict correctly the four years with severe bleaching. A log-log linear relationship was found between SST and the number of days in a give n year above that SST at which severe coral beaching was observed. However, the intra-annual relationship between temperature and the incidence of ble aching suggests that no one simple predictor of the onset of coral bleachin g within a year may be applicable.