Making food using sunshine  Sun

Phytoplankton cells contain chlorophyll like plants on the land.  By using the sun's energy the chlorphyll converts water and carbon dioxide (CO2) into oxygen (O2) and sugars.  The sugars are food for the plant and the oxygen is excreted by the cell. 

 

Chlorophyll Photosynthesis

 

Phytoplankton produce around 50% of the world's oxygen and reduce carbon dioxide levels in the atmosphere.