Uptake of plastic microbeads by ciliate Paramecium aurelia

Microplastics (MPs) are small fraction of plastics that are less than 5 mm in length. They are bountiful and widespread pollutants in the aquatic environment. A wide range of organisms which play an important role in the food web, ingest microplastic particles and transfer them to the higher trophic levels. In this work, ingestion of fluorescent polystyrene beads 2 µm of diameter by ciliated protozoa Paramecium aurelia in different concentrations and times of exposure was studied. We studied also the ingestion and clearance rate as well as formation of food vacuoles. The highest uptake of beads by ciliates reached 1047.2 ± 414.46 particles after 10 min of incubation. Food vacuoles formation reflected the ingestion rate of P. aurelia, which increased at higher beads concentration up to the10th minute of incubation and decreased afterwards. On the contrary, the clearance rate persisted to be higher at low concentration. These findings showed that maximum capacity of microplastics ingestion by paramecia depended on beads concentration and on time of exposure.