coral bleaching

Coral bleaching is the process where corals become white due to loss of symbiotic algae and photosynthetic pigments. This loss of pigment can be caused by various stressors, such as changes in water temperature, light, salinity, or nutrients. A bleached coral is under stress, more vulnerable to starvation and disease, and at risk of death. The leading cause of coral bleaching is rising ocean temperatures due to climate change. Take up of carbon dioxide from the atmosphere also has been acidifying the oceans and affects coral health. Large-scale bleaching events can devastate entire reef ecosystems, affecting biodiversity and the livelihoods of coastal communities that depend on healthy reefs for food, tourism, and protection from storm surges. Healthy coral at left, and bleached, but still living, coral at right

According to the United Nations Environment Programme, between 2014 and 2016, the longest recorded global bleaching events killed coral on an unprecedented scale. In 2016, bleaching of coral on the Great Barrier Reef killed 29 to 50 percent of the reef's coral. Bleaching events impact many regions of the world, including Australia, Hawaii, Japan, and more. Natural corals adapted against bleaching and human assistance with reef building may help prevent further damage.