Plankton are the diverse collection of organisms that drift in water (or air) but are unable to actively propel themselves against currents (or wind)

They move thanks to water currents and turbulence, but some animals can move on their own after the planktonic stage, e.g. jellyfish. Plankton is the basis of the food chain, it becomes food for many species of aquatic animals, such as fish and whales. Plankton is very resistant to the availability of nutrients.