Abstract: To investigate the physiological and biochemical responses ofParachlorella kessleriTY to cadmium stress, this study utilized a strain ofP. kessleriTY isolated from Shanxi Province.P. kessleriwere treated with cadmium solutions at mass concentrations of 0, 0.50, 1.50, 3.00, and 5.00 mg/L. Algal samples were collected daily during the stress period to measure growth, pigment content, chlorophyll fluorescence parameters, neutral lipid content, and total lipid content. The results showed that cadmium treatment inhibited the growth ofP. kessleriTY in a mass concentration-dependent manner, with inhibition rates reaching up to 62.9% at the highest mass concentration tested. Although chlorophyll content showed an increasing trend, it was still significantly inhibited （P<0.05）. In the 3.00 mg/L treatment group, carotenoid content reached its highest level among all treatment groups （1.56 mg/L） but remained significantly lower than that of the control group. The chlorophyll fluorescence parameters （Fv/Fm,Fv/Fo, PIABS） of the algal cells decreased significantly with increasing cadmium mass concentration, indicating severely impaired photosynthetic capacity and PS Ⅱ photochemical activity. The protein content inP. kessleriTY exhibited a biphasic response to cadmium treatment, with inhibition at high mass concentrations and promotion at low concentrations. Furthermore, high mass concentrations of cadmium significantly promoted lipid accumulation in the microalgae, with the maximum increase reaching 169%. These findings revealed the toxic effects of cadmium onP. kessleriTY and provide a theoretical basis for its potential application in the treatment of low-concentration cadmium-containing wastewater.

Key words: Microalgae （Parachlorella kessleriTY）, cadmium stress, physiological mechanism, biochemical response, lipid