The resistance of Chlamydomonas reinhardtii cells to the neonicotinoid сlothianidin.

The capacity of algae to withstand the effects of toxic pollution provides a means of survival and subsequent regeneration of the phytoplankton, highlighting the importance of in-depth research of this area for aquatic ecosystems. This study investigated the effects of clothianidin (CL), a commonly used agricultural insecticide, on the freshwater alga Chlamydomonas reinhardtii. The toxic effect of CL depended on both the number of cells and the concentration of the insecticide. Generally, an observed dose-dependent decrease was evident in cell growth, chlorophyll (Chl) content, and photosynthetic efficiency, while carotenoid levels increased. Particular attention has been paid to the ability of C. reinhardtii to survive exposure to lethal concentrations of the CL, which resulted in a 60% decrease in cell number and pronounced Chl bleaching. After the photosynthetic activity had been reduced to almost zero, some cells showed the ability to restore the function of photosynthetic electron transport in a medium containing CL. The algae's resilience is linked to their bioremediation capacity, as evidenced by a 50% reduction in CL concentration (from 0.8 to 0.4 mg/L) within 10 days of exposure. Repeated CL treatments induced resistance in algae, yet this was only observed when the Chl concentration per cell recovered to the control level (2.7 pg Chl/cell). The addition of CL when the Chl/cell was 30% lower than that of the control sample resulted in no observable resistance. Cell aggregation was found to be important in the protective process, while the initial density of cells significantly influenced this effect.