Microplastics (MPs) commonly coexist with microalgae in aquatic environments, can heteroaggregate during their interaction, and potentially affect the migration and impacts of MPs in aquatic environments. The hetero-aggregation may also influence the fate of other pollutants through MPs' adsorption or alter their aquatic toxicity. Here, we explored the hetero-aggregation process and its key driving mechanism that occurred between green microalga Chlorella vulgaris (with a cell size of 2-10 μm) and two types of MPs (polystyrene and polylactide, 613 μm). Furthermore, we investigated the environmental impacts of the microplastics-microalgae aggregates (MPs-microalgae aggregates) by comparing their adsorption of Cu(II) with that of pristine MPs and evaluating the effects of hetero-aggregation on MPs aging and their toxicity to microalgae. Our results indicated that microalgal colonization occurred on the surface of MPs, possibly through electrostatic interactions, hole-filling, hydrophilic interactions, and algae-bacteria symbiosis. The hetero-aggregation led to a stronger Cu(II) adsorption by MPs-microalgae aggregates than pristine MPs due to electrostatic interactions, coordination, complexation, and ion exchange. Exposure to either MPs (pristine or aged) or Cu(II) inhibited the cell growth of C. vulgaris, while the integrated biomarker response (IBR) showed more pronounced inhibitory effects resulting from aged MPs compared to pristine MPs and an antagonistic effect on microalgae was caused by the co-exposure to MPs and Cu(II). These findings suggest that the hetero-aggregation of MPs and microalgae may alter their environmental fates and co-pollutant toxicity.

中文翻译：

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当微塑料遇上微藻：揭示聚集体的动态形成及其对毒性和环境健康的影响


微塑料 （MP） 通常与水生环境中的微藻共存，在相互作用过程中可以异质聚集，并可能影响微塑料在水生环境中的迁移和影响。异质聚集也可能通过 MP 的吸附影响其他污染物的命运或改变其水生毒性。在这里，我们探讨了绿微藻 Chlorella vulgaris（细胞大小为 2-10 μm）和两种类型的 MP（聚苯乙烯和聚丙交酯，613 μm）之间发生的异质聚集过程及其关键驱动机制。此外，我们通过比较微塑料-微藻聚集体 （MPs-微藻聚集体） 对 Cu（II） 的吸附与原始 MP 的吸附，并评估异质聚集对 MPS 衰老的影响及其对微藻的毒性，研究了微塑料-微藻聚集体 （MPs-微藻聚集体） 的环境影响。我们的结果表明，微藻定植发生在 MPS 表面，可能是通过静电相互作用、空穴填充、亲水相互作用和藻类-细菌共生。由于静电相互作用、配位、络合和离子交换，异质聚集导致 MPS-微藻聚集体比原始 MP 更强地吸附 Cu（II）。暴露于 MP（原始或老化）或 Cu（II） 抑制了寻常念珠菌的细胞生长，而综合生物标志物反应 （IBR） 显示与原始 MP 相比，衰老 MP 产生的抑制作用更明显，并且对微藻的拮抗作用是由 MPs 和 Cu （II） 的共同暴露引起的。这些发现表明，MP 和微藻的异质聚集可能会改变它们的环境归宿和共污染毒性。