Corals are marine organisms living in compact colonies of many identical individual polyps. The group includes the important reef builders that inhabit tropical oceans, which secrete calcium carbonate to form a hard skeleton. Coral reefs form some of the most diverse ecosystems on Earth. They occupy less than one tenth of one percent of the world ocean surface, yet they provide a home for about twenty-five percent of all marine species, including fish, molluscs, worms, and crustaceans. Paradoxically, coral reefs flourish even though they are often surrounded by ocean waters that provide few nutrients. University of Miami (UM) Rosenstiel School of Marine & Atmospheric Science scientist Chris Langdon and colleagues have developed a new tool to monitor coral reef vital signs. By accurately measuring their biological pulse, scientists can better assess how climate change and other ecological threats impact coral reef health worldwide.