Linked from
The 36 pages that link to Phytoplankton, each with the reason it gives.
Marine food webBroader topic: They are major primary producers at the base of many marine food webs.
PlanktonBroader topic: These drifting producers supply much of the energy entering marine food webs.
Suspension feedingBroader topic: They are a major source of suspended food for aquatic animals.
AlgaeBroader topic: Many unicellular algae live as drifting phytoplankton in oceans and lakes.
Lake ecosystemBroader topic: These suspended producers form the base of many lake food webs.
SalpBroader topic: These organisms are among the small particles captured by salp feeding nets.