4.3.1—Aquatic primary producers

Phytoplankton are drifting microscopic producers; macrophytes are visible aquatic plants, and both convert light into biomass.

Phytoplankton drift in open water and support consumers as suspended primary production. Macrophytes are visible aquatic plants that may be emergent above the surface, submerged below it or floating; rooted forms also create shelter and breeding structure.

A microscopic cyanobacterium floating in a lake is phytoplankton; reeds rooted at the shore are macrophytes.

Reeds are emergent macrophytes: their visible rooted structure differs from the suspended microscopic biomass of phytoplankton.

Phytoplankton is a functional group, not one plant species; cyanobacteria can be included.