Delayed fluorescence, steady state fluorescence, photosystem II quantum yield as endpoints for toxicity evaluation of Cu2+ and Ag+

•Photosynthetic parameters are less sensitive against toxic noble metals compared to motility parameters.•Delayed fluorescence is comparable or even superior in sensitivity compared to PAM-fluorometry in order to detect effects on the photosynthetic apparatus.•Changes in photosynthetic parameters indicate a deep penetration of a given substance into the cell and can serve as a non-invasive diagnostic tool.