TRANSFORMATION OF CHLORAMPHENICOL AND OXYTETRACYCLINE IN AQUACULTURE POND SEDIMENTS

Transformation processes of two antibiotics, chloramphenicol (CM) and oxytetracycline (OTC), in aquaculture pond sediments collected from a freshwater eel pond and a marine shrimp pond were investigated. The sorption rates of CM in the freshwater and marine sediment slurries (10%, wt/vol) were 4% and 2%, respectively. In contrast, the sorption rates of OTC in the freshwater and marine sediment slurries (10%, wt/vol) were 99.8% and 90.3%, respectively. CM amended at 60-70 mg/L was transformed within 4 days in the freshwater and marine pond sediment slurries when incubated under anaerobic conditions, and within 12 days under aerobic conditions. OTC amended at 60-70 mg/L was not transformed after incubation for 70 days in the freshwater and marine pond sediment slurries under anaerobic conditions. However, OTC wits transformed to undetectable levels within 47 days when incubation proceeded under aerobic conditions. OTC was in fact also removed in the sterile sediment slurries under aerobic conditions during the incubation periods, although its rates of removal were much lower than the rates in the active sediment slurries. The transformation rates of CM were greater under anaerobic conditions than under aerobic conditions at all concentrations (60-400 mg/L).