Abstract

The present study aimed to evaluate the risk assessment, median lethal concentration LC_50-96h, development, and mortality of Nile tilapia Oreochromis niloticus larvae exposed to atrazine after stress management. An LC_50-96h trial was carried out using fish (n = 147; 8.5 ± 1.0 mg; seven larvae/aquarium), which were allocated randomly in 21 aquaria (1 L) and exposed to five concentrations of atrazine: 2, 4, 8, 16, and 32 mg L⁻¹ plus one control (without herbicide) and a control with a solubility adjuvant (acetone). Temperature, pH, dissolved oxygen, conductivity, and total ammonia were measured daily. In addition, a stress test was performed with fish (n = 150; 17.9 ± 1.7 mg; 10 larvae/aquarium) submitted to air exposition (five minutes) and posteriorly distributed randomly in 15 aquaria (1 L), and exposed to atrazine at 0.18, 6, 12, and 18 mg L⁻¹. The LC_50-96h of atrazine for Nile tilapia larvae was 17.87 mg L⁻¹. Significant differences (P < 0.05) were found for weight and final length, pH, and dissolved oxygen that was responsive to the increased levels of herbicide. Larvae mortality post-stress was registered to 6, 12, and 18 mg L⁻¹ of atrazine, and was more critical at 24 h. The increased doses of atrazine used in LC_50-96h test depressed the development of Nile tilapia larvae. Fish submitted to stress (air exposition) and exposed to sub-lethal doses of atrazine showed significant mortality, indicating that stressors may increase the toxic effect of atrazine for Nile tilapia larvae. On the other hand, based on risk assessment atrazine can be classified as herbicide with low toxicity for Nile tilapia larvae and low toxicological risk.

摘要

本研究旨在评估压力处理后暴露于阿特拉津的尼罗罗非鱼Oreochromis niloticus幼虫的风险评估，平均致死浓度LC _50-96h，发育和死亡率。使用鱼（n = 147； 8.5±1.0 mg；七个幼体/水族馆）进行了LC _50-96h试验，将它们随机分配到21个水族馆（1 L）中，并暴露于五种浓度的阿特拉津：2，4， 8、16和32 mg L ^-1加上一个对照（不含除草剂）和一个含溶解性佐剂的对照（丙酮）。每天测量温度，pH，溶解氧，电导率和总氨。此外，对鱼（n = 150； 17.9±1.7 mg； 10个幼体/水族馆）进行了压力测试，暴露于空气中（五分钟），然后随机分布在15个水族馆（1 L）中，并暴露于阿特拉津。 0.18、6、12和18 mg L ^-1。阿特拉津的尼罗罗非鱼幼虫的LC _50-96h为17.87 mg L ^-1。 发现重量和最终长度，pH和溶解氧对除草剂水平增加有显着差异（P <0.05）。应激后幼虫死亡率分别为6、12和18 mg L ^-1阿特拉津，并在24小时时更关键。LC _50-96h测试中使用的_at去津剂量增加，抑制了尼罗罗非鱼幼虫的发育。经受压力（空气暴露）并暴露于亚致死剂量的阿特拉津的鱼显示出显着的死亡率，这表明应激源可能会增加阿特拉津对尼罗罗非鱼幼虫的毒性作用。另一方面，基于风险评估，阿特拉津可分类为对尼罗罗非鱼幼虫低毒且毒理学风险低的除草剂。