Why is phytoplankton important to other organisms?

The collapse of the world's phytoplankton population would have dire consequences for our environment and civilization. Global climate health is affected by phytoplankton population health. Phytoplankton is responsible for approximately 50 percent of all photosynthesis on earth. This means they function as a major carbon dioxide sink, pulling this gas from the atmosphere and creating organic matter and emitting oxygen. In this way the phytoplankton population is a major factor in limiting global warming and in the general atmospheric health of the planet.