Introduction to in vivo chlorophyll measurements

In vivo analysis is the direct measurement of chlorophyll in algal cells without extraction or chemical treatment. Chlorophyll a, the primary photosynthetic pigment in all plants, is a fluorescent molecule for which the concentration can be determined using a fluorometer.

Chlorophyll a fluorescence is the only technique available sensitive enough to detect phytoplankton at natural levels without concentration and extraction. The use of in-situ fluorometers allows chlorophyll levels to be measured rapidly and efficiently without any sample preparation.

The Chlorophyll-containing organisms such as phytoplankton are measured directly in the natural waters. The chlorophyll in the organism is detected with a fluorometer that projects a beam of blue light into the sample, and then detects and displays a reading for the red fluoresced light emitted by the chlorophyll a.

Fluorometric techniques are well established for both qualitative and quantitative measurements of the chlorophylls and pheophytins, see timeline. The in vivo chlorophyll technique alone may satisfy the requirements for many types of qualitative test plans. For situations where more quantitative results are needed, additional procedures are performed that involve the periodic collection of samples to prepare for extraction measurements.