Effect of abiotic factors on the degradation of oxytetracycline in water

Abstract

Oxytetracycline is widely used to treat vibriosis and other bacterial infections in aquaculture systems. Study was conducted to understand the influence of abiotic factors on the degradation of OTC in water. The degradation of OTC was faster in alkaline conditions followed by neutral and acidic conditions. The half-life of OTC in alkaline condition was 1.8 and 1.2 times shorter than in acidic and neutral conditions respectively. Photolysis was the primary influencing factor for the quicker degradation of OTC as only 20% degradation was recorded in the dark in 2 hours as against complete degradation in the presence of light at 45 ppt salinity. The half-life of OTC in seawater (30 ppt) was 54 minutes and was 1.4 times shorter than its half-life in fresh water. Degradation of OTC under different abiotic factors fit well with the first order kinetics. The optimum water characteristics for brackishwater aquaculture viz. alkaline pH between 7.5 to 8.5 and salinity of 25 to 30 ppt facilitates speeder degradation rate of OTC. The study suggests that, India, being in the tropical zone has the advantage of bright sun light throughout the year and thus facilitates swift degradation of OTC as photolysis is the primary factor influencing degradation. The combined effect of all these favourable parameters averts any OTC residues in the pond water and the surrounding aquaculture environment.