Most reef-building corals contain Zooxanthellae, a photosynthetic microscopic algae, in their tissues. Zooxanthellae produce sugar for the corals from photosynthesis; in return, corals obtain the energy to build reefs. These microscopic algae are also great indicators of the ocean’s health and global warming. Ocean warming is the major cause for many reefs dying around the world, as it damages and kills corals. Zooxanthellae can’t survive in the corals when water temperatures are above normal. When water temperatures are only just a few degrees above normal for long periods of time, corals lose their Zooxanthellae. As a result, the corals starve and die. When these corals die, they become “bleached” or white. Coral bleaching proves to us that we need to better manage the Earth’s resources, and strive to reduce our carbon dioxide and other toxic emissions into the atmosphere!