Coral bleaching is the whitening of coral colonies due to the loss of the symbiotic algae, zooxanthellae, from the tissues of coral polyps. It is mostly caused by stress. The host coral polyp provides the algae with a protected environment and a supply of carbon dioxide for its photosynthetic processes. The golden-brown algae serve as a major source of nutrition and color for the coral. The loss of the algae exposes the translucent calcium carbonate skeletons of the coral colony, and the corals look "bleached." Corals may recover from short-term bleaching (less than a month), but prolonged bleaching causes irreversible damage and mortality, for without the algae, the corals starve and die. However, even a sublethal stress may result in increased susceptibility of corals to infections, with resulting significant mortality. Populations of sea urchins, parrot fish, and worms erode and weaken dead reef skeletons, and the...