Phytoplankton are important primary producers in the marine food web. They are microscopic, single-celled organisms that float freely in the ocean. They rely on energy from the sun for photosynthesis and are therefore most commonly found less than 100 metres below the surface. Phytoplankton are eaten by zooplankton.
These are diatoms, under the microscope. Diatoms are one of the most common types of phytoplankton.
