Abstract：
Organisms are generally exposed to target contaminant with stable concentrations in traditional ecotoxicological studies. However, it is difficult to truly represent the dynamics and complexity of actual aquatic pollution for risk management. Contaminants may enter nearby aquatic systems in pulsed exposure, thus resulting in that aquatic organisms will be exposed to contaminants at fluctuating concentrations. Especially during the season of summer, due to the changes in displacement or periodic emissions of veterinary antibiotics in aquaculture, algal blooms occur frequently in surrounding waters, thus leading to eutrophication of the water. Florfenicol (FFC) is currently widely used as a veterinary antibiotic, but the aquatic ecological risks of FFC under concentration fluctuations are still unknown. Therefore, the acute exposure, chronic exposure and pulsed exposure effects of FFC on Microcystis aeruginosa were investigated to comprehensively evaluate the ecological risk of FFC and raise awareness of the pulsed exposure mode. Results indicated that the toxic effects of FFC on M. aeruginosa were dominated by exposure mode, exposure duration, exposure frequency, and exposure concentration. The maximum growth inhibition rate of the 10 μg/L FFC treatment amounted to 4.07% during chronic exposure of 18 days. However, the growth inhibition rate decreased from 55.1% to 19.31% when algae was exposure to 10 μg/L FFC during the first pulsed exposure (8 h). Therefore, when the concentration of FFC was equal under chronic and pulsed exposure, FFC exhibited greater toxicity on M. aeruginosa in short pulsed exposure than in continuous exposure. In addition, repetitive pulsed exposure strengthened the resistance of M. aeruginosa on FFC. The adaptive regulation of algae was related to the duration and frequency of exposure. Above results suggested that traditional toxicity assessments lacked consideration for fluctuating concentrations during pollutant emissions, thus underestimating the environmental risk of contaminant. This investigation aims to facilitate the standardization of pulsed exposure.
摘要：
在传统的生态毒理学研究中，生物体通常暴露于浓度稳定的目标污染物。然而,很难真正代表实际水生污染的动态和复杂性进行风险管理。污染物可能会在脉冲暴露中进入附近的水生系统，从而导致水生生物将暴露于浓度波动的污染物中。尤其是在夏天的季节,由于水产养殖中兽用抗生素的位移或周期性排放的变化，藻类水华经常发生在周围的水域，从而导致水体富营养化。氟苯尼考（FFC）目前被广泛用作兽用抗生素，但浓度波动下FFC的水生生态风险仍未知。因此,急性暴露，研究了FFC的慢性暴露和脉冲暴露对铜绿微囊藻的影响，以全面评估FFC的生态风险，提高对脉冲暴露模式的认识。结果表明，FFC对铜绿假单胞菌的毒性作用以暴露模式为主，暴露持续时间,暴露频率,和暴露浓度。在18天的慢性暴露期间，10μg/LFFC处理的最大生长抑制率为4.07％。然而,在第一次脉冲暴露（8小时）期间，藻类暴露于10μg/LFFC时，生长抑制率从55.1％下降到19.31％。因此,当FFC的浓度在慢性和脉冲暴露下相等时，FFC在短脉冲暴露中对铜绿分枝杆菌的毒性高于连续暴露。此外,重复脉冲暴露增强了铜绿假单胞菌对FFC的抗性。藻类的适应性调节与暴露的持续时间和频率有关。以上结果表明，传统的毒性评估缺乏对污染物排放过程中浓度波动的考虑，从而低估了污染物的环境风险。这项研究旨在促进脉冲暴露的标准化。
