Plankton can be producers, consumers or recyclers, depending on which trophic level they belong to. All plankton are classified as one of three types: phytoplankton, zooplankton and bacterioplankton.
Phytoplankton, such as algae and cyanobacteria, live near the surface of the water and use sunlight to produce energy through photosynthesis. Zooplankton are small, drifting protozoans or animals that feed on other types of plankton, making them consumers. Bacterioplankton include bacteria and archaea, which are saprotrophic organisms that function as recyclers and break down or recycle organic nutrients into nonorganic forms. Plankton is the first and most important layer of the oceanic food chain. The combined weight of all plankton outweighs that of all other sea animals.