Enhancing aggregation of microalgae on polystyrene microplastics by high light: Processes, drivers, and environmental risk assessment

• Published in: Journal of hazardous materials 2024-09, Vol.476, p.135062, Article 135062
• Main Authors: Wang, Chun, Zhang, Yaru, Wang, Changhai, He, Meilin
• Format: Article
• Language: English
• Subjects: Aggregation; Chlorella - drug effects; Chlorella - metabolism; Chlorella - radiation effects; Light; Light intensity; Microalgae; Microalgae - drug effects; Microalgae - radiation effects; Microplastics; Microplastics - chemistry; Microplastics - toxicity; Molecular mechanisms; Polystyrenes - chemistry; Polystyrenes - toxicity; Risk Assessment; Water Pollutants, Chemical - chemistry; Water Pollutants, Chemical - radiation effects; Water Pollutants, Chemical - toxicity
• ISSN: 0304-3894; 1873-3336; 1873-3336
• DOI: 10.1016/j.jhazmat.2024.135062

Microplastics (MPs) are emerging pollutants, causing potential threats to aquatic ecosystems and serious concern in aggregating with microalgae (critical primary producers). When entering water bodies, MPs are expected to sink below the water surface and disperse into varying water compartments with different light intensities. However, how light influences the aggregation processes of algal cells onto MPs and the associated molecular coupling mechanisms and derivative risks remain poorly understood. Herein, we investigated the aggregation behavior between polystyrene microplastics (mPS, 10 µm) and Chlorella pyrenoidosa under low (LL, 15 μmol·m−2·s−1), normal (NL, 55 μmol·m−2·s−1), and high light (HL, 150 μmol·m−2·s−1) conditions from integrated in vivo and in silico assays. The results indicated that under LL, the mPS particles primarily existed independently, whereas under NL and HL, C. pyrenoidosa tightly bounded to mPS by secreting more protein-rich extracellular polymeric substances. Infrared spectroscopy analysis and density functional theory calculation revealed that the aggregation formation was driven by non-covalent interaction involving van der Waals force and hydrogen bond. These processes subsequently enhanced the deposition and adherence capacity of mPS and relieved its phytotoxicity. Overall, our findings advance the practical and theoretical understanding of the ecological impacts of MPs in complex aquatic environments. [Display omitted] •Light availability regulates the aggregation behavior between MPs and microalgae.•Light-dependent secretion of algal EPS plays a crucial bridging role in aggregation.•The formation of MPs-microalgae aggregates is driven by non-covalent interaction.•Algal aggregation changes the environmental behaviors and bioeffects of MPs.