Inappropriate practices and lack of regulations regarding antimicrobial use in agricultural production of developing countries increase the risk of exposure to aquatic ecosystems. Sediments may act as sink of antimicrobial compounds and can provide a historical record of pollution. In the present study, toxic potential of sediments receiving effluents from a fish farm (TIL1), rice farm (AZ) and swine farm (RD2) and from a reference natural wetland (PV) in a tropical dry region was evaluated. According to local surveys of antimicrobials and national product registries, sites were classified from highest to lowest potential exposure as following: RD2>TIL1>AZ>PV. Both, whole sediment and interstitial water tests, showed a high toxicity of pig farm sediments to the behavior of Anodontites luteola and the survival of Daphnia magna (EC50 -48hrs: 2.4 -11.8%) (ANOVA, p < 0.05). Integrated responses from Cholinesterase activity (ChE), Gluthathion-S-transferase (GST) and Lipoperoxidation (LPO) measured in A. luteola tissue pointed at the pig and rice farms as sites influenced by activities with an intensive use of xenobiotic substances. The assessment of toxicity pointed at the need of more research on sub-lethal effects of antimicrobials on aquatic invertebrates. With this purpose, we analyzed biomarker response of A. luteola to oxytetracycline in vitro and found a decrease of ChE and GST in concentrations of 100 microg I(-1).