Click here to see the absorption spectra for chlorophyll a and b . They also produce oxygen as a byproduct. Phytoplankton were among the first organisms to do this and as a result an oxygen holocaust occurred. In order to survive, organisms evolved the ability to use this oxygen and aerobic respiration evolved. This set the stage for life as we know it today.
Phytoplankton also serve as a major source of oxygen and sink for carbon dioxid e.
As such, they are extremely important in the environment. Both, however, are shorter in wavelength when compared to the visible spectrum. However, ozone depletion has compromised the atmosphere's ability to protect life from this radiation. These atoms are very reactive and combine to from ozone. For every ten million molecules of air, two million are breathable oxygen, and only three are ozone.