Wang Zhen-Fang, Han Zi-Yu, Wang Meng-Xue, Ma Yi-Chi, Wang Ting, Wang Li-Qing, Zhang Wei
Centre for Research on Environmental Ecology and Fish Nutrient(CREEFN)of the Ministry of Agriculture, Shanghai Ocean University, Shanghai 201306, China.
Key Laboratory of Exploration and Utilization of Aquatic Genetic Resources, Ministry of Education, Shanghai Ocean University, Shanghai 201306, China.
Huan Jing Ke Xue. 2020 Jun 8;41(6):2688-2697. doi: 10.13227/j.hjkx.201912227.
Enrofloxacin (ENR), a fluoroquinolones antibiotic, is widely used in the medical and aquaculture fields. Its residues in surface waters in China are high. However, few studies have evaluated both its toxicity to phytoplankton and the degradation or removal by microalgae. In this study, the growth, photosynthetic activity, and exopolysaccharides (EPS) of freshwater micro-green algae sp. and the dynamics of ENR concentrations (0, 5, 25, 50, and 100 mg·L) were studied through an exposure experiment for 12 days. Results showed that the biomass and photosynthetic pigment content of sp. increased with increasing exposure time in each treatment; however, it showed a significant inhibitory effect on the growth and pigment accumulation of sp. compared with the control group (<0.01). The LC of ENR to sp. was (241.29±7.33) mg·L after 96-h exposure, indicating that sp. could adapt to the stress conditions of high concentration ENR. Meanwhile, when the concentration of enrofloxacin was<5 mg·L, it was found to promote the maximum photosynthetic rate (/) of sp. On the contrary, when the concentration of enrofloxacin was>5 mg·L, photosynthetic inhibition was observed (<0.01). The actual photosynthetic rate (Yield) and the maximum electron transfer rate (ETR) showed a trend of initially decreasing and then increasing in 12 days. It can gradually adapt to the stress conditions and recover certain photosynthetic activity after 6 days' exposure. In addition, ENR can also stimulate the EPS (RPS and CPS) release. At the end of the experiment, the removal rates of ENR in the four control groups (no algae addition groups) (5, 25, 50, and 100 mg·LENR) were 7.27%, 5.56%, 5.30%, and 4.88%, respectively, while the removal rates of the treatment groups were 3.21, 3.01, 2.69, and 2.83 times of the no algae groups, indicating that sp. had a significant promoting effect on the removal of ENR (<0.01). Overall, our results can provide new insights for the understanding of the ecological toxicity of fluoroquinolone antibiotics to primary producers in the aquatic system and also provide new ideas for the ecological removal of antibiotic residues in water bodies and the biological resource utilization of freshwater microalgae.
恩诺沙星（ENR）是一种氟喹诺酮类抗生素，广泛应用于医学和水产养殖领域。其在中国地表水中的残留量较高。然而，很少有研究评估其对浮游植物的毒性以及微藻对其的降解或去除情况。在本研究中，通过为期12天的暴露实验，研究了淡水微绿藻的生长、光合活性和胞外多糖（EPS）以及恩诺沙星浓度（0、5、25、50和100mg·L）的动态变化。结果表明，在各处理中，藻的生物量和光合色素含量随暴露时间的增加而增加；然而，与对照组相比，其对藻的生长和色素积累表现出显著的抑制作用（<0.01）。暴露96小时后，恩诺沙星对藻的LC50为（241.29±7.33）mg·L，表明藻能够适应高浓度恩诺沙星的胁迫条件。同时，当恩诺沙星浓度<5mg·L时，发现其促进了藻的最大光合速率（Pmax）。相反，当恩诺沙星浓度>5mg·L时，观察到光合抑制（<0.01）。实际光合速率（Yield）和最大电子传递速率（ETR）在12天内呈现先下降后上升的趋势。暴露6天后，它能逐渐适应胁迫条件并恢复一定的光合活性。此外，恩诺沙星还能刺激EPS（RPS和CPS）的释放。实验结束时，四个对照组（无藻添加组）（5、25、50和100mg·L恩诺沙星）中恩诺沙星的去除率分别为7.27%、5.56%、5.30%和4.88%，而处理组的去除率分别是无藻组的3.21、3.01、2.69和2.83倍，表明藻对恩诺沙星的去除具有显著的促进作用（<0.01）。总体而言，我们的研究结果可为理解氟喹诺酮类抗生素对水生系统中初级生产者的生态毒性提供新的见解，也可为水体中抗生素残留的生态去除以及淡水微藻的生物资源利用提供新思路。
