Department of Botany, School of Biology, Aristotle University of Thessaloniki, GR-54124, Thessaloniki, Greece.
Laboratory of Environmental Research and Education, Democritus University of Thrace, Nea Hili, GR-68100, Alexandroupolis, Greece.
Ecotoxicol Environ Saf. 2020 Feb;189:109925. doi: 10.1016/j.ecoenv.2019.109925. Epub 2019 Dec 16.
Information on silver nanoparticle (AgNP) phytotoxicity on seagrasses is provided for the first time. Toxic effects of environmentally relevant AgNP concentrations on Halophila stipulacea were assessed to identify sensitive biomarkers, to determine threshold effect concentrations and to evaluate potential risks. Potential alterations in the cytoskeleton, endoplasmic reticulum, cell ultrastructure and viability, oxidative stress parameters and elongation in H. stipulacea leaves exposed to AgNP concentrations ranging from 0.0002 to 0.2 mg L for 8 days were examined. The first signs of actin filament (AF) response in differentiating cells, exhibiting disorientation and slight bundling, were observed on the 4th day at 0.0002 mg L, while at the end of the experiment and at the higher concentrations, AFs were extremely bundled. Endoplasmic reticulum was affected in meristematic and differentiating cells; massive aggregations and loss of the "grainy" structure were observed, initially on the 6th day at 0.002 mg L. Effects on microtubules were detected on the last day at 0.2 mg L. An increase in HO levels on the 4th and/or 6th day even at 0.0002 mg L was followed by a decrease on, or up to the last day. On the 6th day at the lowest concentration, elevated malondialdehyde content, and superoxide dismutase and peroxidase activity were detected, indicating oxidative damage and antioxidant defense mechanism activation. Dead epidermal cells mainly occurred at 0.02 and 0.2 mg L, while no dead vein cells were detected. A significant inhibition in leaf elongation was observed only at 0.2 mg L. Therefore, AF disturbance in differentiating leaf cells, being a susceptible response parameter, could be regarded as an early warning indicator of risk posed by AgNPs to H. stipulacea meadows, while most of the remaining parameters examined also constitute useful biomarkers. The lowest observed effect concentration (0.0002 mg L), being within the range of environmentally relevant AgNPs concentrations, suggests the possibility of negative impacts of AgNPs on seagrass health. A risk quotient of 1.33 was calculated, indicating that AgNPs may pose a significant potential risk to the coastal environment. The data presented highlight the importance of future research to further investigate the seagrass-AgNP interactions, stress the need for a refinement of the environmental risk assessment of AgNPs and could be utilized for the design of biomonitoring programs for rational management of the coastal environment.
首次提供了关于银纳米颗粒（AgNP）对海草植物毒性的信息。评估了环境相关浓度的 AgNP 对 Halophila stipulacea 的毒性影响，以确定敏感生物标志物、确定阈值效应浓度并评估潜在风险。在暴露于 0.0002 至 0.2mg/L AgNP 浓度 8 天的海草叶片中，检测到细胞骨架、内质网、细胞超微结构和活力、氧化应激参数的潜在改变以及伸长。在第 4 天，在 0.0002mg/L 时，观察到分化细胞中肌动蛋白丝（AF）反应的最初迹象，表现出取向和轻微的束状；而在实验结束时和较高浓度下，AF 则极度束状化。内质网在分生组织和分化细胞中受到影响；最初在第 6 天，在 0.002mg/L 时观察到大量聚集和“颗粒状”结构丢失。在第 8 天，在 0.2mg/L 时检测到微管的影响。即使在 0.0002mg/L 时，第 4 天和/或第 6 天 HO 水平的增加随后在第 8 天下降或持续到第 8 天。在最低浓度下，第 6 天检测到丙二醛含量升高，超氧化物歧化酶和过氧化物酶活性升高，表明氧化损伤和抗氧化防御机制激活。仅在 0.02 和 0.2mg/L 时观察到表皮细胞死亡，而叶脉细胞未观察到死亡。仅在 0.2mg/L 时观察到叶片伸长的显著抑制。因此，分化叶片细胞中 AF 紊乱作为敏感反应参数，可视为 AgNP 对 H. stipulacea 草地构成风险的早期预警指标，而其余大多数检查的参数也构成有用的生物标志物。观察到的最低效应浓度（0.0002mg/L）处于环境相关 AgNP 浓度范围内，表明 AgNP 可能对海草健康产生负面影响。计算出的风险商数为 1.33，表明 AgNP 可能对沿海环境构成重大潜在风险。所呈现的数据强调了进一步研究海草-AgNP 相互作用的重要性，强调了需要细化 AgNP 的环境风险评估，并可用于设计生物监测计划，以实现沿海环境的合理管理。
