Bleached anemone on a reef. The bleached anemone appears pale and white. Like corals, anemones can become bleached when the anemone ejects the symbiotic algae that live in its tissues. The algae normally make food for the anemone by photosynthesis, so lack of them impairs the functioning of the anemone, and can be fatal. Anemones bleach due to stress, which is usually caused by a rise in water temperature or acidity. Bleaching events are closely monitored by researchers investigating the effects of global warming and ocean acidification. Filmed in Palau.