Interactive effects of microplastics and ciprofloxacin on aquatic microbial decomposers

Environmental contamination by microplastics (MP) of aquatic ecosystems is increasing worldwide, making this thematic of global concern. Although it is still poor know their effects as individual contaminants, the possibility of other contaminants to bind MPs can overwhelm the problem. Plant litter decomposition is a key ecological process in freshwaters, where microbial decomposers, play an important role by transferring nutrients and energy to higher trophic levels. The mail goal of this study was to evaluate the interactive effects between MP and ciprofloxacin (CIP), in plant litter decomposition and associated to microbial communities. For this, leaves were immersed in a stream to allow microbial colonization and exposed in microcosms individually and in mixtures to MP (5, 50 and 500 mg L-1 ) and CIP (0.01, 0.1, 1 and 10 mg L-1 ). Leaf mass loss was stimulated by the presence of CIP, while the activity of the extracellular enzyme was inhibited with increasing MP concentrations. The structure of fungal communities changed by the presence of CIP, and fungal reproduction was inhibited by increasing MP concentrations. Moreover, significant antagonistic effects between MP and CIP were found, highlighting the importance to considerer the effects of mixtures of contaminants in further studies to better understand their impacts on ecosystem processes and associated communitie