Combined effects of microplastics and temperature on the competition between Brachionus havanaensis and Brachionus calyciflorus (Rotifera)

Abstract Aquatic organisms are constantly exposed to effluents which often contain microplastics. Microplastics adversely affect aquatic organisms as a result of mechanical damage during ingestion or intoxication by chemicals adsorbed on the microplastics. Sub-optimal temperatures may acerbate the adverse effects of microplastics on aquatic biota. Brachionid rotifers, such as Brachionus havanaensis and Brachionus calyciflorus , are common in tropical freshwaters. They are generalist filter feeders capable of consuming microplastic particles of a wide size range 0.05 to 40 µm, which can eventually affect growth and competitive interactions among species. Here, we evaluated the effect of 30 µm beads of polystyrene microplastics at 10 and 20 mg l −1 on the population growth and competition of B. havanaensis and B. calyciflorus at 20 and 25 °C using 0.5 × 10 6 cells ml −1 Chlorella vulgaris as food. Population growth decreased in treatments with microplastics at both temperatures as compared to the controls. The population growth rates ranged between 0.21 and 0.38 d −1 for B. calyciflorus, and between 0.27 and 0.48 d −1 for B. havanaensis . The presence of the competing species significantly lowered the population growth rate for B. calyciflorus but not for B. havanaensis . On the other hand, while the presence of the microplastics had little impact on the population growth rate of B. calyciflorus in the presence of the competitor, the reverse was true for B. havanaensis , especially at 20 °C. Our results show that the presence of microplastics may affect rotifer community structure in natural water bodies.