Influence of oxytetracycline on the fate of nitrogen species in a recirculating aquaculture system

Common aquaculture practices include the use of certain pharmaceuticals such as antibiotics in avoiding diseases and promoting a healthier growth of the culture. The aim of this study is to monitor and assess the influence of different low oxytetracycline concentrations on the transformation of nitrogen compounds under aeration condition in a lab-scale recirculating aquaculture system (RAS). Over 1 mg L-1 dose of oxytetracycline to aquaculture had induced ammonia(NH4-N), nitrate(NO3-N), soluble COD accumulation in RAS. In addition, nitrous oxide (N2O) emission from RAS was significantly reduced during the oxytetracycline dose periods. After ceasing the dose of oxytetracycline, ammonia oxidation and nitrous oxide re-emission were observed. This observation indicated that low concentrations of oxytetracycline could affect the nitrogen species in RAS. Also, the emission mechanisms of N2O may not be only dependent on nitrification process but also dependent on denitrification process in our RAS system.