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The Effects of Microplastics on Growth and Photosynthetic Activity of Chlorella pyrenoidosa: The Role of Types and Sizes
Summary
Researchers exposed the freshwater alga Chlorella pyrenoidosa to polystyrene and PVC microplastics across three size ranges for 14 days, finding that smaller particles caused greater growth inhibition — up to 43% — and that algae responded by secreting extracellular polymers and forming aggregates to resist the particles.
The effects of different types and sizes of microplastics on microalgae have not been systematically studied. Here, the microalga Chlorella pyrenoidosa was exposed to three particle sizes (1 ~ 10, 10 ~ 100, and 100 ~ 500 μm) of polystyrene (PS) and polyvinyl chloride (PVC) for 14 days. Cell density indicated a general inhibitory effect of microplastics (MPs) on the growth of Chlorella pyrenoidosa. The maximum inhibition was found to be 42.7% in 1 ~ 10 μm (PS), and the growth inhibition was negatively correlated with particle size. The inhibitory effects of PS are stronger than those of PVC. Moreover, PS and PVC depressed chlorophyll a content but stimulated light energy utilization efficiency (Fv/Fm, Ik, ETRmax, α) in all particle size ranges. FTIR analysis and SEM image displayed that Chlorella pyrenoidosa resisted the effects of MPs by aggregation, which may be related to the secretion of EPS. These results revealed the long-term effects of different types and sizes of MPs on freshwater microalgae and provided a reference for exploring the ecotoxicity of MPs.