Over the last decade, concerns have been raised regarding the potential health and environmental effects associated with the release of metal oxide nanoparticles (NPs) into ecosystems. In the present work, the potential hazards of nickel oxide (NiO) NPs were investigated using the ecologically relevant freshwater alga Pseudokirchneriella subcapitata. NiO NP suspensions in algal OECD medium were characterized with regard to their physicochemical properties: agglomeration, surface charge, stability (dissolution of the NPs) and abiotic reactive oxygen species (ROS) production. NiO NPs formed loose agglomerates and released Ni²⁺. NiO NPs presented a 72 h-EC₅₀ of 1.6 mg L⁻¹, which was evaluated using the algal growth inhibition assay and allowed this NP to be classified as toxic. NiO NPs caused the loss of esterase activity (metabolic activity), the bleaching of photosynthetic pigments and the intracellular accumulation of reactive oxygen species (ROS) in the absence of the disruption of plasma membrane integrity. NiO NPs also disturbed the photosynthetic process. A reduction in the photosynthetic efficiency (Φ_PSII) accompanied by a decrease in the flow rate of electrons through the photosynthetic chain was also observed. The leakage of electrons from the photosynthetic chain may be the origin of the ROS found in the algal cells. The exposure to NiO NPs led to the arrest of the cell cycle prior to the first cell division (primary mitosis), an increase in cell volume and the presence of aberrant morphology in the algal cells. In this work, the use of different approaches allowed new clues related to the toxicity mechanisms of NiO NPs to be obtained. This work also contributes to the characterization of the environmental and toxicological hazards of NiO NPs and provides information on the possible adverse effects of these NPs on aquatic systems.

在过去的十年中，人们越来越关注与金属氧化物纳米颗粒（NPs）释放到生态系统中有关的潜在健康和环境影响。在目前的工作中，使用与生态有关的淡水藻类次生伪藻研究了氧化镍（NiO）NPs的潜在危害。在藻类OECD介质中的NiO NP悬浮液的理化特性进行了表征：团聚，表面电荷，稳定性（NPs的溶解）和非生物活性氧（ROS）的产生。NiO NPs形成松散的团块并释放Ni ²⁺。NiO NPs的72 h-EC ₅₀为1.6 mg L ^-1，使用藻类生长抑制测定法对其进行了评估，并将该NP归类为有毒物质。在不破坏质膜完整性的情况下，NiO NPs引起酯酶活性（代谢活性）的损失，光合色素的漂白和活性氧（ROS）的细胞内积累。NiO NPs也干扰了光合作用过程。光合作用效率降低（_ΦPSII）伴随着通过光合作用链的电子流率的降低也被观察到。电子从光合链的泄漏可能是藻类细胞中发现的ROS的起源。暴露于NiO NPs导致细胞周期在第一次细胞分裂之前停止（原代有丝分裂），细胞体积增加，藻类细胞出现异常形态。在这项工作中，使用不同的方法可以获得与NiO NPs毒性机制有关的新线索。这项工作还有助于表征NiO NP的环境和毒理学危害，并提供有关这些NP对水生系统可能产生的不利影响的信息。