Can microplastics variability drive the colonization dynamics of periphytic protozoan fauna in marine environments?

In recent years, microplastics have become a global environmental hot topic of concern. To explore the effects of different concentrations of microplastics on colonization dynamics of periphytic protozoan fauna, a 21-day study was conducted in temperature-controlled circulation systems. Periphytic protozoan communities were used as test organisms and exposed to five concentrations of MPs: 0, 1, 5, 25, and 125 mg l^-1, identification and enumeration were conducted on days 3, 5, 7, 10, 14 and 21. The results showed that the colonization dynamics were driven by MPs and significantly shifted at concentrations over 5 mg l^-1. However, a notable decline in maximum species richness and abundance was observed in the high concentrations of microplastic, along with significant deviations in colonization patterns from the control group (0 mg l^-1). Therefore, it is suggested that the colonization dynamics of periphytic protozoa can serve as a bioindicator for assessing microplastic concentrations in marine environments.