A great variety of animals inhabit the open ocean biome. They range in size from microorganisms that can only be seen with microscopes and provide the base for many food chains to the mammoth blue whale that can be up to 110 feet long. Sunlight can penetrate up to 650 feet deep in some parts of the ocean. Ninety percent of all marine life lives in the upper zone of the ocean that receives sunlight.
The open ocean is home to numerous types of plankton. Plankton are any animals, protists, plants, or bacteria that float freely with the current of the water. The plankton form the foundation of almost every food chain of marine life.