Sea surface temperature variability in Panamá and Galápagos: Extreme temperatures causing coral bleaching

We examined associations between warm sea surface temperature (SST) anomalies and coral bleaching in the Galápagos Islands and the Gulf of Panamá, in the tropical eastern Pacific Ocean. Interannual SST variability is dominated by the El Niño-Southern Oscillation phenomenon at Galápagos, whereas only strong events have an SST signature in Panamá. We explored various SST-related metrics potentially associated with bleaching occurrence: maximum absolute SST, SST anomaly, and the combined effect of intensity and duration of both SST anomalies (described via a "degree days" index) and high SST events. In Galápagos, three Niño years (1983, 1987, and 1992) coincided with bleaching. These were the top three years in both maximum annual SSTs and degree days values. In Panamá, bleaching in 1983 coincided with high maximum SSTs and high degree days. In contrast, no bleaching was detected in 1972 despite high values of both quantities. We found all temperature-related metrics to be highly correlated, and it was impossible to isolate their effects.