Phytoplankton from the North Sea collected by means of a
plankton net. During spring time diatoms are dominating
The term plankton refers to organisms - mainly microorganisms - that are floating through the water. They may be motile, but they cannot swim against currents in the water column. Planktonic organisms that carry out photosynthesis form the phytoplankton. On a global annual scale the phytoplankton brings about the same primary production as the plants on land.