Chronic exposure to CuO nanoparticles induced community structure shift and a delay inhibition of microbial functions in multi-species biofilms

Abstract

Periphytic biofilms have served as a potentially important environmental media of contaminants removal and an important indicator of the health of aquatic systems. When the nanoparticles (NPs) released, they are likely to encounter periphytic biofilms, and then their ecosystem functioning might be changed. Here, we explored the long-term (28 days) impacts of CuO NPs (μM magnitude) on the microbial biomass, metabolic activities, community structure and associated ecosystem-level processes in multi-species biofilms inoculated from lake water. Slight aggregation of CuO NPs was observed during the exposure experiment. All of the algal, fungal, and bacterial community structure in biofilms were already altered by seven days of exposure to 0.781 and 7.81 μM CuO NPs, but a series of functional endpoints did not show clear differences, suggesting the functional redundancy within biofilm communities. After 28 days, however, a wide range of microbial endpoints that are specific to autotrophs (photosynthetic yield) or heterotrophs (basal respiration) or enzymes that represent the target communities were significantly affected. These decreases matched with the total copper content in biofilms, and indicated the negative effects of CuO NPs on the primary production and nutrient cycling of biofilms. Overall, the response of biofilms to CuO NPs produced a slow and delayed effect on microbial-mediated functions over community structure. These results highlight the highly sensitive responses of biofilms in fresh water to CuO NP, suggesting that CuO NPs (at environmentally relevant doses) would, although changes are slow, affect the biofilms’ functioning and services, such as their sustainability for purification of polluted surface water.