Hi Anvar, This is a ...

Hi Anvar,

This is a difficult one, as the amount of chlorophyll per cell will depend on the type of algae.  So while chlorophyll will give you an overview of the algal load, and can be very good for comparative work, it doesn't necessarily equate to a specific number of cells.  Some algae have other photosynthetic pigments in addition to chlorophyll, so the chlorophyll per cell is lower.  If you are dealing with one main algal species for the majority of the time, you may be able to produce a calibration curve based on your own measurements of algal numbers, but if the algal species present change on a seasonal or other basis, it won't necessarily be accurate at all times of year.

Sorry I can't give you a more definitive answer.