Coral lives a symbiotic life. Inside the sac of each coral polyp lives one-celled algae called zooxanthellae.Algae gives off oxygen and other nutrients that the coral polyp needs to live and in return the polyp gives the algae carbon dioxide and other substances the algae needs.
Warm ocean currents raise the temperature in cold areas while the cold currents decrease the temperature in warm ocean areas.The Labrador current which is a cold current, lowers the temperature near the north-east coast of North America.