Accumulation, metabolism and elimination of enrofloxacin in 

submerged macrophytes in simulated ecosystem

LI Chuanbu1，2， WANG Yuan2， ZHAO Shu2， FAN Peili2， 

LING Hai1，2， LI Xincang2， ZHOU Junfang2， FANG Wenhong2

(1. Key Laboratory of East China Sea Fishery Resources Exploitation and Utilization, Ministry of Agriculture and Rural affairs, 

East China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Shanghai200090, China; 2. National 

Pathogen Collection Center for Aquatic Animals, College of Fisheries and Life

 Science, Shanghai Ocean University, Shanghai201306, China)

Abstract: In order to evaluate the efficiency of antibiotic removal of submerged macrophytes from aquaculture tail water, HPLC method for the determination of enrofloxacin and ciprofloxacin in submerged macrophytes was established based on the improved QuEChERS pretreatment method. The accumulation, metabolism and elimination of enrofloxacin residue in submerged macrophytes were studied in simulated ecosystem. The effects of different extraction solution, extraction salt and extraction time on the recovery were optimized, and the purification effect of different purification agents was investigated. The recovery rates of enrofloxacin and ciprofloxacin in submerged macrophytes were 79.60 %110.15 % and 57.26 %102.00 %, respectively. The detection limits were 0.003 μg·g-1 and 0.005 μg·g-1, respectively. In simulated ecosystem, Vallisneria natans, Elodea nuttallii and Hydrilla verticillata were exposed to enrofloxacin of final concentration of 200 μg·L-1, respectively. The maximum enrofloxacin concentration of 0.82 μg·g-1, 0.86 μg·g-1 and 2.34 μg·g-1 were determined at 24 h after the exposure. The areas under the curves (AUC) were 192.06 （μg·g-1)·h, 209.92 (μg·g-1)·h and 471.44 (μg·g-1)·h, respectively. The bioaccumulation coefficients (FBC) of enrofloxacin were 9.7, 10.2 and 27.8, respectively. The concentrations of ciprofloxacin, the metabolite of enrofloxacin, reached the highest value at 72 h after the exposure, which were 0.027 μg·g-1, 0.029 μg·g-1 and 0.037 μg·g-1 respectively, and showed a slow downward trend after 300 h; the area under the curves(AUC) were 8.42 (μg·g-1)·h, 8.21 (μg·g-1)·h and 12.21 (μg·g-1)·h, respectively. Results showed that submerged macrophytes could effectively accumulate enrofloxacin residue in aquaculture tail water, and Hydrilla verticillata was significantly better than Vallisneria natans and Elodea nuttallii. The results provided a theoretical basis for the treatment of antimicrobial residues in aquaculture tail water. The submerged macrophytes can absorb antibiotics from the aquatic environment through  roots and leaves, and then migrate and transform them into other metabolites in the macrophytes, which plays a certain role in the degradation of antibiotics in the aquatic environment. In aquaculture, insitu degradation or translocation degradation of antibiotics by aquatic plants has the characteristics of low cost, high efficiency and green environmental protection, which has a considerable application prospect in aquaculture tail water treatment. HPLC method for the determination of enrofloxacin and ciprofloxacin in submerged macrophytes was established based on the improved QuEChERS pretreatment method. Finally, 1% formic acid acidified acetonitrile was selected as the extraction solution, 1.0 g NaCl as the extraction salt. The sample was purified with 50 mg PSA and 5 mg GCB, and was extracted by vortex for 15 min. The recovery rates of enrofloxacin and ciprofloxacin in submerged macrophytes were 79.60%110.15% and 57.26%102.00%, respectively. The detection limits were 0.003μg·g-1 and 0.005 μg·g-1, respectively.

In order to evaluate the removal efficiency of antibiotics in submerged macrophytes from aquaculture tail water, the experiment was carried out in simulated ecosystem.  Vallisneria natans, Elodea nuttallii and Hydrilla verticillata were chosen to investigate its absorption, elimination and removal effects of antibiotics. They were separately exposed to  enrofloxacin of final concentration of 200 μg·L-1,respectively. The maximum enrofloxacin concentration of 0.82 μg·g-1, 0.86 μg·g-1 ,2.34 μg·g-1were determined at 24 h after the exposure. The areas under the curves (AUC) were (192.06 μg·g-1)·h, 209.92 (μg·g-1)·h,471.44 (μg·g-1)·h, respectively. The bioaccumulation coefficients (FBC) of enrofloxacin were 9.7, 10.2 and 27.8, respectively. The concentrations of ciprofloxacin, the metabolite of enrofloxacin, reached the highest value at 72 h after the exposure, which were 0.027 μg·g-1, 0.029 μg·g-1 and 0.037 μg·g-1 respectively, and showed a slow downward trend after 300 h; the areas under the curves(AUC)were 8.42 (μg·g-1)·h,8.21 (μg·g-1)·h, 12.21 (μg·g-1)·h, respectively.  Results showed that submerged macrophytes could effectively accumulate enrofloxacin residue in aquaculture tail water, and Hydrilla verticillata was significantly better than Vallisneria natans and Elodea nuttallii in accumulation effects. These results provided a theoretical basis for the treatment of antimicrobial residues in aquaculture tail water.

Keywords: enrofloxacin; submerged macrophytes; accumulation, metabolism and elimination; simulated ecosystem; HPLC method