Abstract：
Due to increasing anthropogenic perturbation and water eutrophication, cyanobacterial blooms (CYBs) have become a global ecological and environmental problem. Toxic CYBs and elevated pH are considered to be the two key stressors associated with eutrophication in natural waters, particularly in the event of CO2 depletion induced by dense blooms. However, previous research has been focused on investigating the impacts of toxic CYBs or pH changes in isolation, whereas the interactive effects of such stressors on edible bivalves that inhabit CYB waters still lack information. In this study, the combined effects of toxic Microcystis aeruginosa and pH shifts on the antioxidant responses, immune responses, and apoptosis of the edible freshwater bivalve Corbicula fluminea were explored. The results showed that the activity of antioxidant enzymes was significantly impacted by the interactive effects between toxic M. aeruginosa exposure and time course, yet pH shifts showed no significant effects on the activities of these antioxidant enzymes, implying that the antioxidant response in C. fluminea was mainly triggered by toxic M. aeruginosa exposure. Toxic M. aeruginosa also induced an increased production of reactive oxygen species and malondialdehyde in treated clams, particularly under high pH settings. The elevated lysosomal enzyme activity helped C. fluminea defend against toxic M. aeruginosa exposure under high pH conditions. The principal component analysis (PCA) and the integrated biomarker response (IBR) results suggested that the treated clams were subjected to the elevated toxicity of toxic M. aeruginosa in conditions of high pH. The heat shock proteins-related genes might be triggered to resist the oxidative damage in treated clams. Moreover, the upregulation of TNF and casp8 genes indicated the potential activation of the caspase8-mediated apoptotic pathway through TNF receptor interaction, potentially resulting in apoptosis. The TUNEL assay results further confirmed that apoptosis appeared in treated clams. These findings improve our understanding of the combined toxicological effects of harmful algae and pH shifts on bivalves, which will provide insights into a comprehensive ecological risk assessment of toxic CYBs to edible bivalve species.
摘要：
由于人为扰动和水体富营养化的增加，蓝藻水华已成为全球性的生态环境问题。有毒的CYBs和升高的pH值被认为是与自然水域富营养化相关的两个关键压力源。特别是在浓密的花朵引起的CO2消耗的情况下。然而,以前的研究一直集中在调查有毒CYBs或pH值变化的影响，然而，这种压力源对栖息在CYB水域的可食用双壳类的相互作用仍然缺乏信息。在这项研究中,毒性铜绿微囊藻和pH值变化对抗氧化反应的联合影响，免疫反应，并探索了可食用的淡水双壳类Corbiculafluminea的细胞凋亡。结果表明，毒性铜绿假单胞菌暴露与时间进程的交互作用显著影响抗氧化酶的活性，然而，pH值变化对这些抗氧化酶的活性没有显着影响，这意味着流感梭菌的抗氧化反应主要是由有毒的铜绿假单胞菌暴露引起的。有毒的铜绿假单胞菌也诱导了活性氧和丙二醛在处理的蛤类的生产增加，特别是在高pH设置。溶酶体酶活性的升高有助于C.fluminea在高pH条件下抵御有毒的铜绿分枝杆菌暴露。主成分分析（PCA）和综合生物标志物反应（IBR）结果表明，在高pH条件下，处理过的蛤壳受到毒性铜绿分枝杆菌的毒性升高。可能会触发与热休克蛋白相关的基因来抵抗处理过的蛤壳中的氧化损伤。此外，TNF和casp8基因的上调表明caspase8介导的凋亡途径通过TNF受体相互作用的潜在激活，可能导致细胞凋亡。TUNEL测定结果进一步证实,凋亡出现在处理的蛤壳中。这些发现提高了我们对有害藻类和pH值变化对双壳类动物的综合毒理学影响的理解。这将为有毒CYBs对可食用双壳类动物的全面生态风险评估提供见解。
