Temperature Tolerance Limits

Maximum summer sea temperatures that are just 2 – 3°C above normal values can kill corals . The upper temperature limit of corals depends on where the corals are found. Corals that usually live in cooler conditions, for example, where summer maximum temperatures are 28°C, will be bleached at lower temperatures than corals that usually live in hotter parts of the reef where summer temperatures reach 31°C .

The extent of bleaching also depends on the length of time that the water temperature is raised. A coral which normally grows in summer temperatures of 29°C may have little reaction if exposed to temperatures of 32°C for a few hours, but could bleach if temperatures reach 31°C for a week. It is a combination of the length of time, and the amount by which water temperature exceeds normal maximum values, that is critical in predicting the extent of bleaching .

Thermal Regime of the Great Barrier Reef	Maximum Temperature for 1997/8 Summer	Maximum Temperature for 2001/2 Summer
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