When Corals Turn White

Coral reefs appear to be made of colorful rocks, but corals are actually living animals. Their bright colors come from tiny algae that live inside their tissues. The relationship benefits both: the algae receive shelter, while the corals receive food produced by the algae through photosynthesis. When ocean temperatures rise even slightly above normal for an extended period, this partnership breaks down. Stressed corals expel the algae, and without them they lose their color and turn white, a process called coral bleaching. Bleached corals are not immediately dead, but they are starving. If temperatures return to normal quickly, the algae may return and the corals can recover. If the heat persists, however, the corals die. The Philippines, located within the Coral Triangle, has some of the richest reefs on Earth, which support fisheries and tourism. Scientists warn that more frequent marine heat waves could cause repeated bleaching events, leaving reefs too little time to recover.