Responses of Microcystis aeruginosa to polystyrene microplastics: Growth dynamics and implications for water treatment

The understanding of microplastics (MPs) has advanced significantly with their accumulation in aquatic environments, but their potential impact on cyanobacterial blooms remains inadequately understood. Herein, the dynamic fluctuating effects of polystyrene (PS) on Microcystis aeruginosa were investigated throughout its growth cycle, as well as the action of algal organic matter in the disinfection by-products formation. The maximum inhibition of algal cell growth and phycobiliprotein content by PS during the adaptation phase reached 56.3 % and 76.3 %, respectively. With the extension of exposure time, the inhibitory effect gradually transitions into promotive effect. PS exposure increased the content of extracellular organic matter and enhanced the THMs formation during chlorination, with trihalomethanes concentrations of 62.8 and 101.9 μg/L in the control and PS treatment groups, respectively. Moreover, the reactive oxygen species levels in PS-exposed algal cells were only 71.5 % of those in the control group, and total antioxidant capacity levels, superoxide dismutase and catalase activities were also lower. However, the microcystin content exposed PS was increased to 1.2 times that of the control group. The presence of PS in aquatic environments increases the levels of algal organic matter and microcystin, potentially threatening water quality. This study provides new insights into the combined effects of microplastics on freshwater algae and valuable data on potential risk associated with MPs.