Chlorophyll (Chl) a analysis.

1.  Remove a random sample of 1 or 2 (or more) ml of cyanobacterial culture and add to microfuge tube 
     (1.0 ml sample) or a 15 ml polystyrene conical centrifuge tube (2.0 ml or more sample). Centrifuge at 
     maximum rpm at room temperature in a microfuge (1.0 ml samples) for 1 min or in a clinical centrifuge 
     (2.0 ml sample) for 5 min.

2.  Remove 90% of the liquid with a pipetman or pipet and then add an equivalent amount of 100% methanol               
     to the liquid pellet; yields 90% methanol final concentration. Any variation of volumes is fine, as long 
     as one extracts with 90% methanol. Mix vigorously on a micromixer (vortex) to fully suspend the pellet.  
     Allow to extract for at least 5 min in the dark.

3.  Centrifuge methanolic extract as in harvesting cells (step 2).

4.  Add 600 ml of methanolic extract to a semimicro cuvette (1.0 ml sample) or 1.8 ml of methanolic extract                
     to a standard cuvette (2.0 ml sample).  Read Absorbency at 665 nm against a 90% methanol blank.

5.  Based on an extinction coefficient of 78.74 liter/gram/cm for Chl a in 90% methanol, multiply the A665 
     by 12.7 to obtain ug Chl a per ml (the value 12.7 is derived from 1/78.74 x 103).  Adjust for any sample
     dilution or concentration.

Reference on extinction coefficient, Meeks and Castenholz. 1974. Arch. Mikrobiol. 78:25-41.