Rapid ecotoxicological bioassay of nickel and cadmium using motility and photosynthetic parameters of Euglena gracilis

The effects of heavy metals Cd and Ni on the movement and photosynthetic parameters of Euglena gracilis were studied during short-term and long-term exposure. Movement and orientation parameters were assessed using the versatile ECOTOX bioassay system, whereas stress on photosynthesis performance was determined using Pulse Amplitude Modulated (PAM) fluorometry. Movement parameters show significant sensitivity to these heavy metals in comparison to photosynthetic parameters. EC50 values (concentration of heavy metals that suppress 50% of measured parameters) of motility for Cd and Ni were 0.86 and 10 mg l−1, respectively, after 1 day of exposure. Concentrations of 22.5 mg l−1 Ni and 50 mg l−1 Cd induce significant effects on photosynthetic yield after 1 and 5 day incubation, respectively. This underpins the suitability of E. gracilis as a bioassay model for monitoring of water toxicity.