Scientists have found that coral bleaching events are occurring more frequently, with the intervals between major bleaching episodes now as short as six years. The finding, published by Terry Hughes from the Australian Research Council Centre for Excellence for Coral Reef Studies at James Cook University and a host of co-authors in Science in 2018, points to an increased likelihood of annual bleaching in the future.
Coral bleaching is a response by corals to environmental stress, usually an increase in water temperature. The zooxanthellae, or tiny algae that live in the coral tissues and generate food by photosynthesis, are expelled and the remaining coral skeleton appears white. Although not dead, bleached corals are severely compromised. They can recover, but a shortening interval between bleaching events hinders their ability to do so. Climate studies show that the temperature conditions that lead to bleaching are becoming more and more common.