Occurrence, distribution and risk assessment of antibiotics at various aquaculture stages in typical aquaculture areas surrounding the Yellow Sea.

The pollution of antibiotics commonly existed throughout the entire aquaculture process, but the residues of antibiotics at different aquaculture stages have rarely been studied. This study investigated the occurrence, distribution and risk assessment of antibiotics at different aquaculture stages (the non-aquaculture stage, the early aquaculture stage, the middle aquaculture stage, and the late aquaculture stage) in two typical marine aquaculture areas (Mahegang River and Dingzi Bay) surrounding the Yellow Sea. Fluoroquinolones and tetracyclines were commonly used antibiotics in the aquaculture of these areas with high detection frequencies (17% to 83%). Compared among four aquaculture stages, the highest concentration of antibiotics (9032.08 ng/L) in aquaculture ponds was detected at the late aquaculture stage. And the antibiotic pollution level of natural water was directly related to the aquaculture stages. Similarly, at the aquaculture stages, the detection frequency of antibiotics in sediments was higher than that at the non-aquaculture stage. Based on the correlation analysis, the concentration of main antibiotics in water showed a positive correlation with total nitrogen (p<0.05) and chlorophyll a (p<0.01), while it showed a negative correlation with salinity (p<0.01) in coastal water of the Dingzi Bay. According to the risk assessment, with the development of aquaculture stages, the selection pressure of fluoroquinolones and tetracyclines on resistant bacteria had increased. And the ecological risks caused by sulfonamides and tetracyclines to aquatic organisms had also increased markedly. Overall, this study may provide a reference for formulating regulatory policies regarding antibiotic use at different aquaculture stages.

Antibiotics in mariculture organisms of different growth stages: Tissue-specific bioaccumulation and influencing factors.

Maricultured organisms are chronically exposed to water containing antibiotics but the bioaccumulative behavior of antibiotics in exposed organisms at different growth stages has received little attention. Here, we investigated the concentrations and tissue-specific bioaccumulation characteristics of 19 antibiotics during three growth stages (youth stage, growth stage, and adult stage) of various organisms (Scophthalmus maximus, Penaeus vannamei, Penaeus japonicus, and Apostichopus japonicus) cultivated in typical marine aquaculture regions, and explored the factors that could affect the bioaccumulation of antibiotics. Tetracyclines (TCs) and fluoroquinolones (FQs) were the dominant antibiotics in all organisms, and the total concentrations of the target antibiotics in fish (S. maximus) were significantly higher than those in shrimp (P. vannamei and P. japonicus) and sea cucumber (A. japonicus) (p < 0.01). The bioaccumulation capacity of a class of statistically significant antibiotics in most samples was strongest during the youth stage and weakest during the adult stage. The antibiotics exhibited higher bioaccumulation capacity in lipid-rich tissues (fish liver and shrimp head) or respiratory organs (fish gill) than muscle. Our results also reveal significant metabolic transformation of enrofloxacin in fish. Different from previous studies, the logarithm bioaccumulation factor (log BAF) was positively correlated with log Dlipw in low-biotransformation tissues (fish gill and muscle) rather than lipid-rich tissues (fish liver). Based on the calculated hazard quotients (HQ), doxycycline in fish muscle may pose a distinct risk to human health, which deserves special attention. Overall, these results provide insight into the bioaccumulation patterns of antibiotics during different growth stages and tissues of maricultured organisms.