What kind of protist is plankton?

Plankton is a diverse group of microorganisms that includes both phytoplankton and zooplankton. Phytoplankton are primarily photosynthetic protists, such as diatoms and dinoflagellates, which contribute significantly to oxygen production and carbon cycling in aquatic environments. Zooplankton, on the other hand, include small protozoans and larval stages of larger animals, serving as key components of the aquatic food web. Together, they play crucial roles in marine and freshwater ecosystems.