Physiological responses of Chlorella vulgaris upon coexposure to β-lactam antibiotics and Ag NPs.

The present study investigated the joint effects of β-lactam antibiotics and silver nanoparticles (Ag NPs) on Chlorella vulgaris (C. vulgaris). The results show that when a single analyte was treated with amoxicillin (AM), aztreonam (AZ) and Ag NPs, the growth of C. vulgaris significantly decreased with increasing exposure concentration. The 96 h median effect concentration (EC50) was determined, and the toxicity of the three substances decreased in the order of Ag NPs > AZ > AM. In the cotreatments, the joint effects of Ag NPs and antibiotics on C. vulgaris were synergistic. Similarly, scanning electron microscopy (SEM) images also revealed that compared with coexposure, single-analyte exposure caused less damage to C. vulgaris. Grey correlation analysis was employed to assess the impact of combined β-lactam antibiotics and Ag NPs on the aforementioned indicators. Our findings contribute greatly to a better understanding of the joint effects of β-lactam antibiotics and Ag NPs on aquatic organisms and can provide solid evidence for ecological risk assessment of the coexistence of β-lactam antibiotics and Ag NPs in aquatic environments.