Negative bottom-up effects of sulfadiazine, but not penicillin and tetracycline, in soil substitute on plants and higher trophic levels.

Veterinary antibiotics are widely used in livestock production and can be released to the environment via manure, affecting non-target organisms. Recent studies provide evidence that antibiotics can adversely affect both plants and insects but whether antibiotics in soil also affect trophic interactions is unknown. We tested whether antibiotics grown in sand as soil substitute with environmentally relevant concentrations of penicillin, sulfadiazine and tetracycline affect the survival of aphids feeding on plants (two crop and one non-crop plant species). Apera spica-venti, Brassica napus, and Triticum aestivum individuals were infested with aphids that were monitored over four weeks. We did not observe effects of penicillin or tetracycline on plants or aphids. However, sulfadiazine treatments reduced plant growth and increased mortality in the two tested grass species, but not in B. napus. Sulfadiazine subsequently decreased aphid density indirectly through reduced host plant biomass. We thus show that an antibiotic at realistic concentrations in a soil substitute can affect several trophic levels, i.e. plants and herbivores. This study contributes to the environmental risk assessment of veterinary antibiotics as it implies that their use potentially affects plant-insect interactions at environmentally relevant concentrations.