The Effect of Mixed Microplastic on Freshwater Microalgae Growth and Survival

The increasing microplastic concentration in freshwater ecosystems has caused a significant threat to the microalgae community’s survival and growth. However, past studies have mainly focused on the effect of a single microplastic polymer on microalgae. Therefore, this research assessed the effect of mixed microplastic (PP and PVC) on freshwater microalgae growth and survival. The collected microalgae community sample was distributed into triplicates of one control flask (no microplastics) and five flasks with different levels of microplastics: 0%PP + 100%PVC, 25%PP + 75%PVC, 50%PP + 50%PVC, 75%PP + 25%PVC, and 100%PP + 0%PVC. The microalgae were allowed to grow undisturbedly in a lab environment for around nine days, and the chlorophyll level was measured for each flask. The result shows that the microalgae community grew faster in the environment with microplastic than in the environment without microplastic; control group chlorophyll a mean absorbance, measured at 405nm wavelength, was 0.0927, and microplastic group chlorophyll a mean absorbance was 0.1547 (p-value: 0.1633). There was convincing evidence that the microalgae community samples grew significantly faster in the PP microplastic dominant environment (mean chlorophyll a absorbance: 0.2032) than in the PVC microplastic dominant environment (mean chlorophyll a absorbance: 0.1182) with a p-value of 0.0426. The results of this research indicate that microplastic can facilitate the growth of microalgae despite its known toxicity to algal populations. This positive effect of microplastic can potentially be used in algal biomass production, which is a valuable renewable resource.