Bleaching and Mortality Thresholds: How Much Is Too Much?

  • R. BerkelmansEmail author
Part of the Ecological Studies book series (ECOLSTUD, volume 233)


Development of a suitable metric for temperature, light and other meteorological variables that adequately predicts bleaching and can be universally applied is challenging. This study presents and evaluates metrics for the prediction of bleaching and mortality thresholds for the most bleaching sensitive species at a number of reef locations across the Great Barrier Reef. Classification tree analysis showed that of the 17 variables examined, sea surface temperature (SST) is the most important variable explaining bleaching events, with the top three explanatory variables being maximum, average and minimum SST. Light, UV and other environmental factors were only weakly correlated with bleaching events. Time-integrated bleaching thresholds were generally found to be an appropriate and useful method for modelling thermal stress in corals. At a small number of locations, however, bleaching thresholds had increased since the major 2002 bleaching event, potentially as a result of acclimatization or adaptation. Mortality thresholds developed for a limited number of reefs based on time–temperature curves for 50% mortality of specific taxa indicate a very narrow margin between the bleaching and mortality thresholds for sensitive species.



Allunga Exposure Laboratories are gratefully acknowledged for making their weather observations over the last 35 years available, including the most comprehensive data set on solar and UV radiation for the Townsville area. The Australian Bureau of Meteorology kindly contributed data on sun hours and other weather variables for the Townsville area.


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Copyright information

© Springer International Publishing AG, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Australian Institute of Marine ScienceTownsville MCAustralia

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