Department of Environmental Health, College of Public Health, East Tennessee State University, Johnson City, Tennessee 37614-1700, United States.
Environ Sci Technol. 2012 Jul 17;46(14):7755-62. doi: 10.1021/es204055c. Epub 2012 Jun 27.
This study investigated the potential impacts of low-concentration citrate-coated silver nanoparticles (citrate-nAg; 2 μg L(-1) as total Ag) on the interactions of Daphnia magna Straus (as a prey) with the predatory dragonfly ( Anax junius : Odonata) nymph using the behavioral, survival, and reproductive end points. Four different toxicity bioassays were evaluated: (i) horizontal migration; (ii) vertical migration; (iii) 48 h survival; and (iv) 21 day reproduction; using four different treatment combinations: (i) Daphnia + citrate-nAg; (ii) Daphnia + predator; (iii) Daphnia + citrate-nAg + predator; and (iv) Daphnia only (control). Daphnia avoided the predators using the horizontal and vertical movements, indicating that Daphnia might have perceived a significant risk of predation. However, with citrate-nAg + predator treatment, Daphnia response did not differ from control in the vertical migration test, suggesting that Daphnia were unable to detect the presence of predator with citrate-nAg treatment and this may have potential implication on daphnids population structure owing to predation risk. The 48 h survival test showed a significant mortality of Daphnia individuals in the presence of predators, with or without citrate-nAg, in the test environment. Average reproduction of daphnids increased by 185% with low-concentration citrate-nAg treatment alone but was severely compromised in the presence of predators (decreased by 91.3%). Daphnia reproduction was slightly enhanced by approximately 128% with citrate-nAg + predator treatment. Potential mechanisms of these differential effects of low-concentration citrate-nAg, with or without predators, are discussed. Because silver dissolution was minimal, the observed toxicity could not be explained by dissolved Ag alone. These findings offer novel insights into how exposure to low-concentration silver nanoparticles could influence predator-prey interactions in the fresh water systems.
本研究通过行为、生存和繁殖终点，调查了低浓度柠檬酸钠包裹的银纳米粒子（柠檬酸钠-银；2μg/L 作为总银）对大型溞（作为猎物）与捕食性蜻蜓（蜻蜓目：蜻蜓）幼虫相互作用的潜在影响。使用四种不同的毒性生物测定法进行了评估：（i）水平迁移；（ii）垂直迁移；（iii）48 小时生存；（iv）21 天繁殖；使用四种不同的处理组合：（i）大型溞+柠檬酸钠-银；（ii）大型溞+捕食者；（iii）大型溞+柠檬酸钠-银+捕食者；和（iv）仅大型溞（对照）。大型溞通过水平和垂直运动来避开捕食者，表明大型溞可能已经察觉到捕食的重大风险。然而，在用柠檬酸钠-银+捕食者处理时，在垂直迁移测试中，大型溞的反应与对照没有区别，这表明在柠檬酸钠处理下，大型溞无法检测到捕食者的存在，这可能对由于捕食风险而导致的大型溞种群结构产生潜在影响。48 小时生存测试显示，在存在捕食者的情况下，大型溞个体在测试环境中死亡率显著升高，无论是否存在柠檬酸钠-银。单独使用低浓度柠檬酸钠-银处理可使大型溞的平均繁殖率提高 185%，但在存在捕食者的情况下繁殖率严重受损（降低 91.3%）。用柠檬酸钠-银+捕食者处理可使大型溞繁殖率提高约 128%。讨论了低浓度柠檬酸钠-银，无论是否存在捕食者，产生这些不同影响的潜在机制。由于银的溶解很少，因此观察到的毒性不能仅用溶解的银来解释。这些发现为低浓度银纳米粒子暴露如何影响淡水系统中的捕食者-猎物相互作用提供了新的见解。
