Impacts of Microplastics on Photosynthetic Efficiency and Pigment Composition in Chlorella pyrenoidosa

The presence of polyethylene (PE) and polystyrene (PS) microplastics affects the ability of the microalga Chlorella pyrenoidosa to carry out photosynthesis efficiently and regulate its pigments. C. pyrenoidosa is an important primary producer in aquatic ecosystems. This study evaluates the impacts of different concentrations of microplastics on chlorophyll and carotenoid levels over a four-day period by precisely measuring optical density at 680 nm and quantifying the amounts of these compounds. The findings reveal a distinct decline in photosynthetic performance that is directly related to the concentration of the substance. This decline is particularly evident in the considerable decrease in the Fv/Fm ratios, which serve as a crucial measure of photosystem II efficiency. Significantly, when the microplastic concentrations were greater (250 mg/L and 500 mg/L), the Fv/Fm ratios plummeted to levels that were roughly 50% lower than those seen in the control samples. This indicates a serious degradation of the photosynthetic machinery. In addition, there was a significant decrease in the concentrations of chlorophyll a and b, with reductions of up to 40% and 35% respectively at the highest concentrations of microplastics examined, compared to the control group. Carotenoid levels also experienced a decrease, although it was not as noticeable, declining by around 25% under comparable circumstances. The results of this study have significant ecological consequences, suggesting that the presence of microplastic pollution could significantly reduce the ability of aquatic systems to produce energy from sunlight, thereby causing disruptions in the food chain and overall deterioration of ecosystem health. The study highlights the importance of conducting further research on the long-term effects of microplastics on photosynthetic organisms in water and emphasizes the necessity of implementing effective measures to decrease microplastic pollution in both marine and freshwater ecosystems.