Coral Reefs
Living organisms make up unique structures in the water that we know as coral reefs. These unusual reefs can be found in shallow and tropical marine water that has almost no nutrients in it. Water that is concentrates with high nutrient levels harm the reef because of the algae that it produces. Reefs extend from 30°N to 30°S of the equator, but they do not grow deeper than 100 ft. or where the temperature of the water falls below 16 °C (72 °F).