The focus of this dissertation is assessment of the potential impact of livestock production practices on terrestrial and aquatic ecosystems by studying the environmental fate and effects of two classes of veterinary antibiotics: macrolides (represented by tylosin) and sulfonamides (represented by sulfamethazine). These antibiotics are widely used in livestock production for disease treatment and prevention, as well as growth promotion. Each has also been widely detected in surface waters in the U.S. The work presented utilized laboratory experiments to study the fate (mobility, dissipation, binding,
and degradation) in soil columns and aquatic microcosms, and bioavailability to benthic invertebrates. Additionally, methodologies were developed for using a passive sampling, or biomimetic, device to estimate bioavailability in aquatic ecosystems. Results suggest the potential persistence of some antibiotic residues in sediments, and the level of bioaccumulation in Lumbriculus variegatus, an aquatic oligochaete, indicates that uptake by sediment-dwelling invertebrates may be a concern.