The third image in this sequence showswhere phytoplankyton are not photosynthisizing efficiently. The blue areas show high levels of photosynthisis. Where the phytoplankton is struggling, it is converting sunlight into fluorescence instead of growth and appears red. All plants fluoresce. Hold an ordinary houseplant under a black light and it glows red.
Florescent intensity is dependent on how successfully a plant is using sunlight.
Plants in environmentally challenging places will convert that light into radiative energy, or fluorescence. The greater the glow, the less efficiently the plant is photosynthesizing. A Simulation -A researcher places a vial of water saturated with phytoplankton in front of a high intensity lamp. Filters block all but the fluorescent wavelengths of light emitted by the suspended cells. By adding an herbicide specifically tailored to curtail photosynthesis, we see via time lapse a gradual increase of fluorescence as the cells less efficiently convert sunlight into growth.