Plankton are sea creatures. They produce oxygen for the creatures that are in the ocean. They start life in the ocean and they also produce oxygen for people, not just fish.Another thing is that they are food for whales and several other animals.
Plankton are important because they produce oxygen for the Earth and they are one of the things that produce oxygen, kind of like trees on the land of Earth.
Currently plankton is not doing well because all of the pollution and the toxic spills that are happening all over the world. The pollution is too much for them to take and now they are in danger.