Temporal dynamics, key influencing factors and source tracking of antibiotics in the biofloc zero-change aquaculture system

Abstract

As environmental pollutants, antibiotic residues have become a research hotspot. The source, transfer, and influencing factors of antibiotics in the biofloc zero-change aquaculture system remain uncertain. The biofloc zero-change shrimp system during the cycle of shrimp production of a typical aquaculture enterprise in China were investigated. Sulfadiazine and erythromycin-H2O were the dominant antibiotics in source water, pond water, biofloc, and feed. The total concentrations of antibiotics (TCAs) in source water and pond water increased, and were significantly higher (1.28–3.91 times) in source water than those in pond water at the corresponding stage (p<0.05). Pearson correlation showed that positive correlations were observed between suspended solids (SS), chemical oxygen demand (COD) and erythromycin-H2O, with correlation coefficients of 0.84 and 0.82, respectively (p<0.01). Multivariable linear regression analysis showed that COD was positively correlated with the TCAs. RDA demonstrated that COD and SS were positively correlated with erythromycin-H2O. We found that the total amount of antibiotics from feed input throughout the rearing period was 12.24 mg, significantly less than those at the late-stage in the pond water and bioflocs (28.66–29.17 mg) in a shrimp pond. The total amount of antibiotics in the source water of the same volume as the aquaculture pond was 27.90–35.07 mg. This study demonstrates that COD and SS are critical factors affecting the transfer and distribution of antibiotics in the biofloc zero-change aquaculture system, and that source water is the most critical source of antibiotics in the aquaculture system.