Tóm tắt
Sea temperatures in many tropical regions have increased by almost 1°C
over the past 100 years, and are currently increasing at ~1–2°C
per century. Coral bleaching occurs when the thermal tolerance of corals and
their photosynthetic symbionts (zooxanthellae) is exceeded. Mass coral
bleaching has occurred in association with episodes of elevated sea
temperatures over the past 20 years and involves the loss of the zooxanthellae
following chronic photoinhibition. Mass bleaching has resulted in significant
losses of live coral in many parts of the world. This paper considers the
biochemical, physiological and ecological perspectives of coral bleaching. It
also uses the outputs of four runs from three models of global climate change
which simulate changes in sea temperature and hence how the frequency and
intensity of bleaching events will change over the next 100 years. The results
suggest that the thermal tolerances of reef-building corals are likely to be
exceeded every year within the next few decades. Events as severe as the 1998
event, the worst on record, are likely to become commonplace within 20 years.
Most information suggests that the capacity for acclimation by corals has
already been exceeded, and that adaptation will be too slow to avert a decline
in the quality of the world’s reefs. The rapidity of the changes that
are predicted indicates a major problem for tropical marine ecosystems and
suggests that unrestrained warming cannot occur without the loss and
degradation of coral reefs on a global scale.
