Energy
Phytoplankton are algae that are responsible for a large portion of the earth's oxygen. "According to many estimates, 70 percent or more of the oxygen in every breath you take can be traced back to marine phytoplankton." Both of these phyla are able to produce energy by photosynthesis, the process of converting the sun's energy to a usable form of energy, which occurs in their chloroplasts. These chloroplasts "contain chlorophyll, the pigment molecule that allows plants and other photosynthetic organisms to capture solar energy and convert it into usable chemical energy in the form of simple sugars." Because they do so, most organisms of the phyla bacillariophyta and dinoflagellata are photoautotrophs.
This picture demonstrates the oxygen production of phytoplankton. "During food production (photosynthesis) using sunlight as their source energy, they [phytoplankton] fix carbon dioxide (CO2) into organic compounds. During this process, these microscopic plants consume large amounts of carbon dioxide from atmosphere and release oxygen" (https://www.environmentalatlas.ae/).
Sources: http://www.encyclopedia.com/topic/Diatoms.aspx
Holt McDougal Biology by Stephen Nowicki
https://www.environmentalatlas.ae/
Holt McDougal Biology by Stephen Nowicki
https://www.environmentalatlas.ae/