Toxic impacts of microplastics and tetrabromobisphenol A on the motility of marine microalgae and potential mechanisms of action

Microalgae are primary producers of most marine ecosystems, which are under the threat of emergent pollutants such as microplastics (MPs) and tetrabromobisphenol A (TBBPA). Although motility is critical for the survival and production of microalgae, the impacts of emergent pollutants on this important behavioural characteristic remain unknown. Therefore, the toxic effects of MPs and TBBPA, alone and in combination, on the motility of two microalgae, Platymonas subcordiformis and Dicrateria zhanjiangensis, were investigated in this study. In addition, the impacts of the pollutants on energy supply and oxidative stress status were also assessed to reveal potential underlying mechanisms. Our results demonstrated that the motility (both velocity and mode of swimming) of these microalgae was significantly suppressed by the pollutant tested. Further analysis indicated that microalgae exposed to pollutants had a significantly lower intracellular content of adenosine triphosphate (ATP), which may be due to the disruption of photosynthesis and glycolysis. In addition, our data showed that the pollutants tested imposed significant oxidative stress on the microalgae, which may be another reason for the decline in motility observed. Moreover, the growth of microalgae was significantly inhibited by the pollutants tested, and coexposure to TBBPA and MPs was shown to be more toxic than single exposure. Data obtained indicate waterborne MPs and TBBPA may pose significant threat to marine microalgae and subsequently the health of the marine ecosystem.