A bleached coral is not a dead coral yet; it has just expelled its symbiotic algae and lost almost all its colour. But those algae supply up to about 90% of the polyp energy, so a bleached colony is a starving one. Once the water reaches 30 to 31°C the colours fade and algal density drops; held above 32°C the reef goes bone white while the fish leave. If it cools in time the algae return, whereas ocean acidification keeps the algae but strangles the rate of calcification.
A bleached coral is not a dead coral yet; it has just expelled its symbiotic algae and lost almost all its colour. But those algae supply up to about 90% of the polyp energy, so a bleached colony is a starving one. Once the water reaches 30 to 31°C the colours fade and algal density drops; held above 32°C the reef goes bone white while the fish leave. If it cools in time the algae return, whereas ocean acidification keeps the algae but strangles the rate of calcification.
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