Corals are tiny animals that live in large communities made up of individual polyps that secrete a calcium carbonate substance that hardens and builds up to form the reef structure over time. There are different types of corals, such as brain corals and fan corals, that form different types of structures. The coral polyps live symbiotically with algae that provides them with their food. Disease, temperature extremes and pollution can cause corals to expel the algae, leaving only the white calcium carbonate skeleton behind, an event called coral bleaching. Coral bleaching is a worry with global warming heating up the oceans and carbon dioxide causing the oceans to acidify. Coral reefs are important ecosystems because they support larger communities of fish, mollusks, crustaceans and other sea creatures.
Solitary corals, Heliofungia actiniformis, were forced to endure hyper-thermal stress in an experiment to learn more about coral bleaching. They can be seeing belching 'Symbiodinium' - a form of algae that gives them their color.
Researchers with the Jaffe Laboratory for Underwater Imaging at Scripps Institution of Oceanography at the University of California San Diego have designed a new seafloor imaging system to study corals up close, and the views are amazing.