Occurrence and risks of antibiotics in the Laizhou Bay, China: Impacts of river discharge

The presence of thirteen antibiotics categorized into four different groups (fluoroquinolones, macrolides, sulfonamides and trimethoprim) was investigated in the rivers discharging to the Laizhou Bay and the seawater of the bay, and the impacts of river discharge on the marine environment were assessed. The results revealed that the same antibiotics predominated in both the river water and the seawater. Additionally, the detected antibiotics in the river water were generally higher than those in the inner bay and in the open bay, reflecting the importance of the riverine inputs as a source of antibiotics. Risk assessment based on the calculated risk quotients (RQ) showed that enoxacin, ciprofloxacin, and sulfamethoxazole in the two aquatic environments both posed high ecological risks (RQ>1) to the most sensitive aquatic organisms Vibrio fischeri, Microcystis aeruginosa and Synechococcus leopoliensis, respectively.

► Some selected antibiotics were ubiquitous in the Laizhou bay, North China.
► The same antibiotics also predominated in the rivers discharging to the bay.
► River discharge was an important source of antibiotics in the bay.
► Parts of the antibiotics in the bay posed high ecological risks to some organisms.