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Co-Exposure to Microplastics and Parabens: Implications for Chlorella vulgaris Bioremediation Efficiency
Summary
Researchers exposed the microalga Chlorella vulgaris to polystyrene microplastics and the preservative methylparaben individually and in combination, finding that while oxidative stress spiked early, algal growth largely recovered by day seven, nutrient removal remained high (up to 80% nitrogen), and microplastics acted as vectors that enhanced methylparaben uptake by the algae.
Background: Microplastics (MPs) are pervasive contaminants in aquatic systems and wastewater (WW), with polystyrene microplastics (PS-MPs) posing significant ecotoxicological risks [1]. MPs can also act as carriers for emerging contaminants [2], such as parabens—widely used preservatives frequently detected in WW [3]. Their co-occurrence raises concerns about combined effects on treatment efficiency and ecosystem health. Objective: This study evaluated the individual and combined effects of PS-MPs and methylparaben (MetP) on the physiological responses and bioremediation performance of Chlorella vulgaris in synthetic WW. Methods: C. vulgaris was exposed to 100 mg PS-MPs/L [4] and MetP (0.796 mg/L, [3]), individually and in co-exposure, under controlled growth conditions for 168 h. Microalgal growth, metabolic activity, nutrient removal, and contaminant fate were assessed. Adsorption assays were also performed to evaluate interactions between PS-MPs and MetP. Results: Short-term exposure (72 h) impaired metabolic activity and increased intracellular reactive oxygen species production. However, after 168 h, C. vulgarisrecovered metabolic function, indicating potential activation of adaptive defense mechanisms. PS-MPs caused moderate growth inhibition (14%), while MetP alone or combined with PS-MPs did not significantly affect microalgal growth. Despite physiological stress, nutrient removal remained high, with nitrogen removal up to 80% and phosphorus removal between 63–70%. Also, C. vulgaris removed 21.34 ± 1.12% of MetP, which increased to 26.20 ± 4.44% in the presence of PS-MPs, suggesting a vector effect. The adsorption assays showed that PS-MPs retained 0.61 ± 0.05 mg MetP per g, enhancing its bioavailability, while no significant PS-MPs degradation occurred over 168 h, by the microalga. Conclusions: Overall, C. vulgaris demonstrated resilience under combined contaminant exposure, maintaining WW treatment performance and partially removing organic micropollutants. The interaction between PS-MPs and MetP enhanced contaminant uptake, highlighting the role of MPs as vectors for ECs. These findings support the potential of microalgal systems as eco-efficient solutions for treating WW contaminated with MPs and co-occurring pollutants. Figure 1. Physiological responses and bioremediation efficiency of C. vulgaris under individual and combined exposure to 100 mg PS-MPs/L and 0.796 mg MetP/L, under WW-mimicking conditions.