We can observe phytoplankton with satellite instruments via ocean color remote sensing, primarily with the NASA Goddard Space Flight Center's SeaWiFS instrument and upcoming MODIS instrument. The satellite detects different concentrations of Chlorophyll a with ocean color satellites. All phytoplankton have Chlorophyll a and accessory pigment that are either photosynthetic or photoprotective accessory pigments. Phytoplankton convert sunlight into biomass using a process called photosynthesis. During photosynthesis, phytoplankton use solar radiation, water and carbon dioxide to yield glucose (a carbon form of energy they can utilize) and oxygen.

Overall Equation of Photosynthesis:

6CO₂ + 12H₂O + sunlight à C₆H₁₂O₆ + 6O₂ + 6H₂O

Phytoplankton and other plants use glucose as "building blocks" to grow. Also, through photosynthesis, these microscopic marine plants nourish the entire marine food web.

Finally, phytoplankton are essential because they are a critical part of the ocean biology and in part control the level of carbon dioxide in the atmosphere.