Corals are representative of typical symbiotic organisms. The coral-algal (Symbiodinium spp.) symbiosis drives the productivity of entire coral reefs. In recent years, microplastics (MPs) and nano-plastics (NPs) have been shown to disrupt this symbiosis, leading to coral bleaching. However, how MPs/NPs affect the Symbiodinium spp. is less thoroughly explored. In this work, Dinophyceae Symbiodinium was employed as a model to study the toxicity effects of MPs and NPs with different concentrations (covering environment-related concentration) toward algae in terms of cellular responses, ultrastructure, OJIP kinetics curve and multi-omics. MPs and NPs caused adverse effects on algae growth throughout whole growing phase, with only slight differences observed in the maximal inhibition ratio. In addition to cell surface shrinkage, holes and plate sutures shedding of algae, the presence of distorted thylakoids, plasmolysis and expanded vesicle volume were observed due to the oxidative stress and physical damage caused by MPs/NPs. The results of OJIP kinetics and JIP-test revealed that MPs/NPs-induced deactivation of oxygen-releasing complex (OEC) centers, reduced electron transfer (photosystem II, PSII), and inefficient energy conversion of antenna proteins were the primary factors for photosynthesis reduction. Weighted correlation network analysis (WGCNA) showed that the impairment of photosynthesis further induces metabolic disturbances, including reactive oxygen species (ROS) generation and nucleotide metabolism dysregulation, thereby exacerbating DNA damage in the algae. Proteomics further validate the accuracy of our results and underscore the significance of the phosphatidylinositol (PI) signaling system in algae responding to MP/NPs acclimation. Collectively, our findings provide comprehensive insights into the ecotoxicity of NPs/MPs on symbiotic algae.

中文翻译：

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微塑料和纳米塑料对珊瑚共生藻类 （Dinophyceae Symbiodinium） 的毒性：来自藻类生理学、超微结构、OJIP 动力学和多组学的证据


珊瑚是典型的共生生物的代表。珊瑚-藻类 （Symbiodinium spp.） 共生关系推动了整个珊瑚礁的生产力。近年来，微塑料 （MP） 和纳米塑料 （NP） 已被证明会破坏这种共生关系，导致珊瑚白化。然而，MP/NPs 如何影响 Symbiodinium spp. 尚未得到深入的探索。在这项工作中，以 Dinophyceae Symbiodinium 为模型，研究不同浓度 （覆盖环境相关浓度） 的 MPs 和 NPs 在细胞反应、超微结构、OJIP 动力学曲线和多组学方面对藻类的毒性影响。MP 和 NPs 在整个生长阶段对藻类生长造成不利影响，在最大抑制率方面仅观察到微小差异。除了藻类的细胞表面收缩、孔洞和板缝合脱落外，由于 MPs/NPs 引起的氧化应激和物理损伤，还观察到扭曲的类囊体、浆果分解和扩大的囊泡体积的存在。OJIP 动力学和 JIP 检验结果表明，MPs/NPs 诱导的氧释放复合物 （OEC） 中心失活、电子转移减少（光系统 II，PSII）和天线蛋白能量转换效率低下是光合作用减少的主要因素。加权相关网络分析 （WGCNA） 显示，光合作用的损害进一步诱导代谢紊乱，包括活性氧 （ROS） 的产生和核苷酸代谢失调，从而加剧藻类中的 DNA 损伤。 蛋白质组学进一步验证了我们结果的准确性，并强调了磷脂酰肌醇 （PI） 信号系统在响应 MP/NPs 驯化的藻类中的重要性。总的来说，我们的研究结果为 NPs/MP 对共生藻类的生态毒性提供了全面的见解。