Antibiotics in Aquatic and Terrestrial Ecosystems

Abstract

Antibiotics are widely prescribed for use as human and veterinary medicines. Through waste disposal and inadvertent releases, these compounds are often introduced to terrestrial and aquatic ecosystems. Antibiotics are considered emerging ecological contaminants because of a limited understanding of their occurrence, fate, and effects. Physiochemical properties of antibiotics influencing environmental fate pathways such as partitioning to sediment may not be characterized by calculating K d values from K ow for individual compounds. Similarly, state-of-the-science hydrological models should be coupled with pharmaceutical introduction models and newly derived experimental data to predict fate and transport of antibiotics at the watershed scale. While single-species toxicity tests are useful for understanding impacts on ecosystems, alternative endpoints, focusing on target specific responses and evolutionary conservation of targeted pathways, may need to be developed to assess their antibiotic impacts on terrestrial and aquatic ecosystems. Lotic mesocosms are specifically recommended for antibiotics to assess structural and functional responses of aquatic systems to individual, mixture, and degradate exposures via waterborne and dietary routes. This information will support both prospective (regulatory) and retrospective (postrelease, site specific) ecological risk assessments for antibiotics. Watersheds influenced by confined animal feed operations and effluent-dominated stream ecosystems likely represent worse-case scenarios for antibiotic impacts, particularly in rapidly urbanizing and agricultural intensive areas in arid and semiarid ecosystems.