What is the relationship between coral bleaching and El Niño / La Niña ?
Coral bleaching occurs when sea temperature rises above approximately 28º C, the threshold beyond which corals expel colourful symbiotic algae. Deprived of metabolic by-products generated by algae for extended periods, corals then die. Coral bleaching was particularly pronounced during 1997-98 due to a very strong El Niño occuring that year. The El Niño-related rises in sea temperature were superimposed on a slow upward sea temperature warming trend in some parts of the Pacific and Indian oceans that may be linked to global warming.
