珊瑚在溫暖清澈的熱帶海域淺水，以石灰岩建造牠們的家—珊瑚礁。珊瑚礁雖只佔海床面積的千份之一，但四份之一的海洋生物都居於其中。每個珊瑚由成千上萬隻微小珊瑚蟲組成。當珊瑚受海水氣溫上升影響，珊瑚會排出寄居於它們體內的共棲藻類，令珊瑚白化，最終死亡。有史以來最為嚴重的白化，使澳洲大堡礁面目全非，影響所有寄居當中的海洋生物。
Corals build themselves homes of limestone in the warm, clear, shallow seas of the tropics. Their reefs occupy less than one tenth of one per cent of the ocean floor, yet they are home to a quarter of all known marine species. Each coral is made up of hundreds to thousands of tiny, living coral creatures. When corals are stressed due to increasing ocean temperatures, they expel the symbiotic algae living in their tissues, causing them to turn completely white and eventually die. Some of the most devastating bleaching events known in recorded history have recently occurred in the Great Barrier Reef in Australia, affecting all reef dwellers.
