Temperature modulates AgNP impacts on microbial decomposer activity

Abstract

Silver nanoparticles (AgNP) scan have toxic effects on aquatic species and compromise important ecosystem processes. AgNP impacts have been the focus of much research, but their effects under different environmental contexts, such as the increase in global temperature are difficult to predict. The aim of this study was to evaluate the interactive effects of AgNPs and temperature on the activity and diversity of microbial decomposers of plant litter in streams. Litter-associated microbial communities were exposed in microcosms to increased concentrations of AgNPs (50 to 75000 mu g L-1) and AgNO3 (5 to 7500 mu g L-1) and kept for 21 days at 10 degrees C, 16 degrees C and 23 degrees C. Effects of AgNPs and AgNO3 were assessed based on leaf mass loss and litter-associated microbial communities by measuring microbial diversity, the activity of fungal extracellular enzymes, and fungal biomass and reproduction. Increase in temperature stimulated leaf mass loss, but not fungal biomass and reproduction. Increased AgNP and AgNO3 concentrations inhibited fungal reproduction and diversity, particularly at 23 degrees C. Activities of the extracellular enzymes phenol oxidase and beta-glucosidase were generally higher at 23 degrees C. Microbial communities were mainly structured by AgNP and AgNO3 concentrations more than by temperature. The negative effects of nano and ionic Ag on microbial activity were more pronounced at 10 and 23 degrees C. The behavior of AgNPs was more related to water physical and chemical characteristics (pH) than to temperature. Results highlight the importance of considering different environmental scenarios when examining NP toxicity to freshwater biota and ecosystem processes. (C) 2017 Elsevier B.V. All rights reserved.