Occurrence, source, and the fate of antibiotics in mariculture ponds near the Maowei Sea, South China: Storm caused the increase of antibiotics usage

Antibiotic residues in mariculture environments have been detected globally, while little information is available about their dynamic levels, source, behavior, and fate during the whole culture process. In this study, the dynamic occurrence, bioaccumulation, source, fate, and human dietary risk of 19 antibiotics were investigated in different breeding stages of mariculture ponds near the Maowei Sea, South China. Fourteen antibiotics, including three sulfonamides (SAs), five fluoroquinolones (FQs), three macrolides (MLs), and two chloramphenicols (CAPs), were detected in the mariculture ponds, with FQs being the most abundant antibiotics. Significant variations of antibiotic concentration occurred during the whole culture process. Severe weather, especially typhoons and rainstorms, resulted in the average highest levels of ∑₁₉antibiotics (mean: 567 ng L^-1) in mariculture ponds. The source apportionment estimated for the mariculture ponds showed that direct application was the primary source of antibiotics (91.2%). The antibiotics in mariculture ponds were mainly discharged through aquaculture wastewater (65.8%) and settling particles (33.8%). The estimated annual input of antibiotics into the Maowei Sea was 2.24 times higher through the two main rivers (48.0 kg a^-1) than through the mariculture wastewater (24.1 kg a^-1). The apparent bioaccumulation factors (ABAFs) confirmed that young and adult tilapia accumulated more sulfamethoxazole (SMX) and norfloxacin (NOX), respectively. The result from the estimated daily intakes suggested that the antibiotics in the seafood could not pose a risk to human health by dietary exposure assessment. CAPSULE: Big variation of antibiotic concentration occurred during the whole culture process in the mariculture farms, and the storm increased antibiotic application.