Single and joint bioaccumulation and toxicity of isoproturon and cadmium in green algae (Chlamydomonas reinhardtii)

Xenobiotics like pesticide isoproturon (IPU) and heavy metal cadmium (Cd) are environmental contaminants posing serious impacts on ecosystem. Understanding their toxic and accumulative processes is crucial to uncover insightful mechanisms and minimize health risks. However, the joint effect of IPU and Cd on microorganisms in aquatic ecosystems remains elusive. In this study, Chlamydomonas reinhardtii was selected as a model unicellular organism to evaluate the ecotoxicological effects of IPU and Cd, focusing on biological responses, bioaccumulation capacity, and environmental adaptation. The combined treatment with IPU (0.24 μmol L−1) and/or Cd (20 μmol L−1) for 60 h can induce acute toxicity to C. reinhardtii, reducing chlorophyll and photosynthetic fluorescence, while increasing oxidative damage manifested by lipid membrane peroxides and electrical conductivity. IPU and Cd were accumulated in C. reinhardtii. Interestingly, IPU accumulation in algae was significantly repressed in the presence of Cd, showing a remarkable decrease of 116.7% compared to the IPU treatment alone. Similarly, the Cd concentration in the cells exposed to IPU was reduced by 23.5% compared to Cd treatment alone. Calculation of the bioconcentration factors revealed lower accumulation values of IPU or Cd in algae under Cd+IPU exposure compared to IPU or Cd stress, suggesting an antagonistic interaction between IPU and Cd during absorption by the algae. Furthermore, the activities and transcriptional expression of enzymatic antioxidants such as SOD and APX were significantly induced by Cd stress, whereas the activities of CAT, APX, and PPO significantly increased elevated by IPU. This study provides compelling evidence of the ecotoxicological effects of combined IPU and cadmium contamination on algae, highlighting the potential of algae for bioremediation of environments contaminated with IPU and cadmium.