Ecosystems such as coral reefs, mangroves, kelp forests, and estuaries are found along the continental shelves. Eighty percent of all sea life lives here. Why? Because shallow water and closeness to land provide the conditions needed to support large quantities of life: food, light, and shelter. Algae, like kelp and phytoplankton, contain green, brown, and red pigments that enable them to convert the Sun's energy into food.