Life depends on plankton.

Plankton is made up of microscopic plants (phytoplankton) and animals (zooplankton). Zooplankton feed on phytoplankton and drift with the currents.

Plankton are very important in the marine food chain. The largest fish in the world, the whale shark, feeds on plankton, including krill, as do many of the largest whales.

Half the world’s oxygen


Phytoplankton produce more oxygen than all the forests on land. Like land plants, phytoplankton release oxygen when they photosynthesise.

Scientists are worried that harmful rays from the sun could pass through the hole in the ozone layer and kill phytoplankton, which live mostly in the upper layers of the ocean.

The web of life

Global warming is melting the ice in Antarctica and in the Arctic. Phytoplankton, which feed krill, grow under sea ice. Less sea ice means less phytoplankton for the krill to eat. This means there will be less krill for the whales to eat.


Species Facts

  • Phytoplankton are microscopic plants that live in the sea. They produce more oxygen than all the forests on land
  • Zooplankton are microscopic animals which feed on phytoplankton
  • Plankton is the staple diet of many whales, as well as the world's biggest fish, the whale shark