Pulse amplitude modulated (PAM) fluorometry is a valuable
tool to detect physiological stress and photosynthetic efficiency
both in terrestrial plants (Juneau et al., 2005) and microalgae
(Baker, 2008; White et al., 2011). General PAM parameters include
maximum quantum efficiency (Fv/Fm), alpha (a), relative electron
transport rate (rETR), and light saturation (Ik). Fv/Fm is used to
estimate physiological stress and the Fv/Fm value of phytoplankton
in non-stressed conditions ranges from 0.6 to 0.7. Also,
Fv/Fm value decreases in nutrient stressed cultures, and is
relatively constant in non-stressed cultures (White et al., 2011).