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Title (Primary) Mixture effects of a fungicide and an antibiotic: Assessment and prediction using a decomposer-detritivore system
Author Konschak, M.; Zubrod, J.P.; Baudy, P.; Fink, P.; Pietz, S.; Duque, T.S.; Bakanov, N.; Schulz, R.; Bundschuh, M.
Journal Aquatic Toxicology
Year 2021
Department ASAM; FLOEK
Volume 232
Page From art. 105762
Language englisch
Topic T5 Future Landscapes
Keywords Aquatic fungi; Azoxystrobin; Ciprofloxacin; Gammarus; Leaf litter breakdown
Abstract Antimicrobials, such as fungicides and antibiotics, pose a risk for microbial decomposers (i.e., bacteria and aquatic fungi) and invertebrate detritivores (i.e., shredders) that play a pivotal role in the ecosystem function of leaf litter breakdown. Although waterborne toxicity and diet-related effects (i.e., dietary exposure and microorganism-mediated alterations in food quality for shredders) of fungicides and antibiotics on decomposer-detritivore systems have been increasingly documented, their joint effect is unknown. We therefore assessed waterborne and dietary effects of an antimicrobial mixture consisting of the fungicide azoxystrobin (AZO) and the antibiotic ciprofloxacin (CIP) on microbial decomposers and the shredder Gammarus fossarum using a tiered approach. We compared effect sizes measured in the present study with model predictions (i.e., independent action) based on published data. During a 7-day feeding activity assay quantifying waterborne toxicity in G. fossarum, the leaf consumption of gammarids was reduced by ∼60% compared to the control when subjected to the mixture at concentrations of each component causing a 20% reduction in the same response variable when applied individually. Moreover, the selective feeding of gammarids during the food choice assay indicated alterations in food quality induced by the antimicrobial mixture. The food selection and, in addition, the decrease in microbial leaf decomposition is likely linked to changes in leaf-associated bacteria and fungi. During a long-term assay, energy processing, growth and energy reserves of gammarids were increased in presence of 15 and 500 µg/L of AZO and CIP, respectively, through the dietary pathway. These physiological responses were probably driven by CIP-induced alterations in the gut microbiome or immune system of gammarids. In general, model predictions matched observed effects caused by waterborne exposure on the leaf consumption, energy processing and growth of gammarids during short- and long-term assays, respectively. However, when complex horizontal (interactions between bacteria and aquatic fungi) and vertical (interactions between leaf-associated microorganisms and shredders) interactions were involved, model predictions partly over- or underestimated mixture effects. Therefore, the present study identifies uncertainties of mixture effect predictions for complex biological systems calling for studies targeting the underlying processes and mechanisms.
Persistent UFZ Identifier
Konschak, M., Zubrod, J.P., Baudy, P., Fink, P., Pietz, S., Duque, T.S., Bakanov, N., Schulz, R., Bundschuh, M. (2021):
Mixture effects of a fungicide and an antibiotic: Assessment and prediction using a decomposer-detritivore system
Aquat. Toxicol. 232 , art. 105762