Use of chlorophyll a fluorescence to detect the effect of microcystins on photosynthesis and photosystem II energy fluxes of green algae

► Microcystins affect the photosynthetic efficiency and the flow of energy through photosystem II. ► MC-LF was the most toxic variant, followed by MC-YR, LR and RR. ► Green algae have different sensitivity to microcystins. ► Our results suggest that bioassay based on chlorophyll fluorescence can be used as a rapid tool to detect microcystin.