Without the algae, the coral looks bleached. Researchers at the University of Georgia think they know one reason why some of the world's coral reefs are dying. Their evidence points to rising global temperatures weakening the photosynthesis that keeps corals alive. Coral polyps are tiny animals, which depend for both their color and sustenance on algae that live within their tissue. Collectively, these polyps create coral reefs, which in turn serve as homes to a rich diversity of other life.
Reefs can be huge.
They can also protect coastlines from ocean storms, such as along parts of Florida. Since the problem has surfaced in tropics around the world, scientists suspect a common cause. Local pollution may contribute, but that doesn't explain the widespread weakening of coral reefs, which some scientists believe could be wiped out within a few decades. The main suspect is global warming because corals deteriorate when the water temperature rises above the low 80s. Exactly how the process works is the subject of intense debate.