The effects of antimicrobials on aquatic ecosystems

Antimicrobials are routinely detected in freshwaters, where organisms are exposed to complex mixtures rather than single compounds. This PhD thesis links real-world exposure patterns to ecological responses by integrating four lines of research: environmental occurrence, multi-trophic effects, internal exposure and food-web transfer, and the ecological consequences of advanced wastewater treatment. The results showed that antimicrobial contamination can propagate across connected compartments, and that mixture effects are frequently non-additive and differ across trophic levels. Microbial and community responses were highly context-dependent, varying between water and sediment and with nutrient status and organic matter, while functional endpoints revealed impacts not captured by community structure alone. Food-chain experiments further indicated that limited biomagnification does not preclude ecological risk, as dietary exposure can still impair predator performance. Finally, advanced wastewater treatment reduced chemical pressure but could also restructure microbial communities, highlighting the need to balance removal efficiency with ecological outcomes. Ultimately, this thesis provides a transferable framework to support interdisciplinary research and management of emerging contaminants in aquatic systems.