胶网藻对水体中恩诺沙星的毒性响应及去除作用

恩诺沙星是医药及水产养殖业广泛使用的喹诺酮类抗生素,是我国地表水中残留量较多的抗生素种类之一;然而有关该抗生素对水体中浮游植物毒理作用以及后者对其去除作用的研究还鲜见报道.本研究以绿藻门的胶网藻(Dictyosphaerium sp.)为对象,通过12 d室内培养实验,分析在不同浓度(0、 5、 25、 50和100 mg·L^-1)恩诺沙星暴露的条件下,胶网藻的生长、光合作用活力和胞外多糖的响应变化及其对不同浓度恩诺沙星的去除效率.结果表明,各处理组中胶网藻的生物量和光合色素含量均随培养时间的增加而升高,但与对照组相比,恩诺沙星对胶网藻的生长和光合色素积累均产生显著抑制作用(P<0.01).通过拟合分析,计算出恩诺沙星对胶网藻96 h半数致死浓度(LC₅₀)为(241.29±7.33) mg·L^-1,表明胶网藻能够适应高浓度的恩诺沙星胁迫.同时发现,当恩诺沙星浓度<5 mg·L^-1时,能够促进胶网藻的最大光合速率(F_v/F_m),但浓度>5...

Toxicological Effects of Enrofloxacin and Its Removal by Freshwater Micro-Green Algae Dictyosphaerium sp.

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 Dictyosphaerium sp. and the dynamics of ENR concentrations (0, 5, 25, 50, and 100 mg·L^-1) were studied through an exposure experiment for 12 days. Results showed that the biomass and photosynthetic pigment content of Dictyosphaerium sp. increased with increasing exposure time in each treatment; however, it showed a significant inhibitory effect on the growth and pigment accumulation of Dictyosphaerium sp. compared with the control group (P<0.01). The LC₅₀ of ENR to Dictyosphaerium sp. was (241.29±7.33) mg·L^-1 after 96-h exposure, indicating that Dictyosphaerium sp. could adapt to the stress conditions of high concentration ENR. Meanwhile, when the concentration of enrofloxacin was<5 mg·L^-1, it was found to promote the maximum photosynthetic rate (F_v/F_m) of Dictyosphaerium sp. On the contrary, when the concentration of enrofloxacin was>5 mg·L^-1, photosynthetic inhibition was observed (P<0.01). The actual photosynthetic rate (Yield) and the maximum electron transfer rate (ETR_max) 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·L^-1ENR) 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 Dictyosphaerium sp. had a significant promoting effect on the removal of ENR (P<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.