Influence of chlorophyll concentrations on the reliability of measurements with an oxygen electrode when studying photosynthetic efficiency in bioassays using microalgae

Euglena gracilis and Chlamydomonas reinhardtii were used as model organisms to establish the best conditions for studying photosynthetic efficiency using the Light Pipette - experimental system, which enables sensitive detection of changes in oxygen evolution/consumption and an easy collection and digitalisation of data. Chlorophyll concentrations of 0.005, 0.025, 0.050 and 0.075 mg mL(-1) were investigated using different light regimes. Cultures of E. gracilis at the same chlorophyll concentration absorbed more light (measured at 580 mu mol m(-2) s(-1)) than those of C. reinhardtii. Cell density had a considerable effect on the reliability of measurements. Chlorophyll concentrations between 0.025 mg(Chl) ml(-1) and 0.050 mg(Chl) ml(-1) can be recommended when applying the Light Pipette system in bioassays using microalgae.