The fate of chemical additives and antimicrobial agents applied in Danish freshwater fish farms MORTEN S. BRUUN\ LARS-FLEMMING PEDERSEN2, INGER DALSGAARD1 , PER BOVBJERG PEnERSEN2 AND OLE SoRTKJArn3 Discharges of chemical additives and antimicrobial agents from aquaculture are potentially unwanted substances in the environment. When chemicals are used for water disinfection at a fish farm, the receiving water body will be contaminated. Likewise, treatment of bacterial diseases in aquaculture inevitably leads to environmental release of antimicrobial agents. The current lack of knowledge of the resulting concentrations and their possible effects leaves an open question to the authorities trying to establish meaningWater samples are collected in Kajak tubes at fish farms. (photo by Morten S. Bruun) Chemicals additives are used without a prescription for various purposes in aquaculture production. Chemical additives range from pure oxygen and sodium chloride to such pH regulating substances as limestone and acid. Chemical additives also include disinfectants, such as formaldehyde and hydrogen peroxide, as well as chloramine-T and copper, which are called antifouling agents because of their specific action. Water disinfection is conducted with chemicals to ful threshold values for additives and antimicrobial agents in relation to aquaculture. Background information and general results from a Danish study concerning discharge concentration of additives and drugs from freshwater rainbow trout farms are presented. The present study included measures of chemical additives, such as formaldehyde, chloramine-T, hydrogen peroxide and copper and antimicrobial agents, including sulfadiazine, trimethoprim, oxolinic acid and fiorfenicol, sampled on fish farms during treatment. Decomposition rates of the four chemicals were examined in water and sediment to model and predict actual discharge. Antimicrobial resistance in fish to pathogenic and indigenous bacteria was monitored as well. Unwanted Substances in the Natural Environment Aquaculture effluents have become a focal point in recent years because of potential ecotoxicological effects of applied agents (Gaikowski et al. 2004). Besides fish feed, various other agents are applied to the water. improve rearing conditions and water quality. Chemical additives, such as formaldehyde, chloramine-T and hydrogen peroxide are applied to the water and successively discharged to receiving water bodies (Masters 2004). Antimicrobial agents or antibiotics are approved drugs with antibacterial effects requiring prescriptions by a veterinarian. Antimicrobial agents inhibit or kill disease-causing (and indigenous) bacteria. Some antimicrobial agents are foreign to the natural environment whereas other antibiotics are produced by plants, bacteria and fungi. The presence of antimicrobial agents might promote the development of resistant bacteria, but resistance is naturally found in most environments. Antibiotic release from fish farms appears following fish disease outbreaks and treatments, where prescribed feed coated with antibiotic is fed to the fish for 8-10 days. Regulation of Aquaculture Effluents To regulate aquaculture operations, the Danish Environmental Protection Agency (DEPA) has proposed WORLD AQUACULTURE 57
RkJQdWJsaXNoZXIy MjExNDY=