Antagonistic and synergistic effects of light irradiation on the effects of copper on Chlamydomonas reinhardtii

• Light intensity and spectral composition affect Cu uptake and effects to C. reinhardtii.
• High light (HL) reduced Cu effect on growth inhibition, oxidative stress and damage.
• HL in combination with Cu up-regulated genes involved in the antioxidant responses.
• HL with increased UVB radiation exacerbated Cu uptake and Cu-induced toxic effects.

The present study showed the important role of light intensity and spectral composition on Cu uptake and effects on green alga Chlamydomonas reinhardtii. High-intenisty light (HL) increased cellular Cu concentrations, but mitigated the Cu-induced decrease in chlorophyll fluorescence, oxidative stress and lipid peroxidation at high Cu concentrations, indicating that Cu and HL interact in an antagonistic manner. HL up-regulated the transcription of genes involved in the antioxidant response in C. reinhardtii and thus reduced the oxidative stress upon exposure to Cu and HL. Combined exposure to Cu and UVBR resulted in an increase of cellular Cu contents and caused severe oxidative damage to the cells. The observed effects were higher than the sum of the effects corresponding to exposure to UVBR or Cu alone suggesting a synergistic interaction.