Mixed messages from benthic microbial communities exposed to nanoparticulate and ionic silver: 3D structure picks up nano-specific effects, while EPS and traditional endpoints indicate a concentration-dependent impact of silver ions

• Published in: Environmental science and pollution research international 2016-03, Vol.23 (5), p.4218-4234
• Main Authors: Kroll, Alexandra, Matzke, Marianne, Rybicki, Marcus, Obert-Rauser, Patrick, Burkart, Corinna, Jurkschat, Kerstin, Verweij, Rudo, Sgier, Linn, Jungmann, Dirk, Backhaus, Thomas, Svendsen, Claus
• Format: Article
• Language: English
• Subjects: Algae; Aquatic plants; Aquatic Pollution; artificial indoor streams; Atmospheric Protection/Air Quality Control/Air Pollution; Bacillariophyceae; Bacteria; Biofilms; Biofilms - growth & development; Biological Sciences; Biologiska vetenskaper; Biomass; Biopolymers - analysis; Boundary layers; chlamydomonas-reinhardtii; Chlorophyta - drug effects; Community ecotoxicology; diatom communities; Diatoms - drug effects; Earth and Environmental Science; Ecosystem; Ecosystems; Ecotoxicology; Environment; Environmental Chemistry; Environmental conditions; Environmental Health; Environmental science; Enzymes; Extracellular polymeric; extracellular polymeric substances; Flow velocity; Food chains; Freshwater ecology; Freshwater organisms; heavy-metals; Ions; laser-scanning microscopy; Metal Nanoparticles - toxicity; Microbial activity; Microbial Consortia - drug effects; Microorganisms; Nanoparticles; near-bed turbulence; Periphyton; Pollutants; Research Article; Saccharides; sierra-nevada; Silver; Silver - toxicity; Silver nanoparticles; Silver Nitrate - toxicity; Stream water; Streams; Studies; Surface water; Waste Water Technology; Water Management; Water Microbiology; Water Pollutants, Chemical - toxicity; Water pollution; Water Pollution Control
• ISSN: 0944-1344; 1614-7499
• DOI: 10.1007/s11356-015-4887-7

Silver nanoparticles (AgNP) are currently defined as emerging pollutants in surface water ecosystems. Whether the toxic effects of AgNP towards freshwater organisms are fully explainable by the release of ionic silver (Ag + ) has not been conclusively elucidated. Long-term effects to benthic microbial communities (periphyton) that provide essential functions in stream ecosystems are unknown. The effects of exposure of periphyton to 2 and 20 μg/L Ag + (AgNO 3 ) and AgNP (polyvinylpyrrolidone stabilised) were investigated in artificial indoor streams. The extracellular polymeric substances (EPS) and 3D biofilm structure, biomass, algae species, Ag concentrations in the water phase and bioassociated Ag were analysed. A strong decrease in total Ag was observed within 4 days. Bioassociated Ag was proportional to dissolved Ag indicating a rate limitation by diffusion across the diffusive boundary layer. Two micrograms per liter of AgNO 3 or AgNP did not induce significant effects despite detectable bioassociation of Ag. The 20-μg/L AgNO 3 affected green algae and diatom communities, biomass and the ratio of polysaccharides to proteins in EPS. The 20-μg/L AgNO 3 and AgNP decreased biofilm volume to about 50 %, while the decrease of biomass was lower in 20 μg/L AgNP samples than the 20-μg/L AgNO 3 indicating a compaction of the NP-exposed biofilms. Roughness coefficients were lower in 20 μg/L AgNP-treated samples. The more traditional endpoints (biomass and diversity) indicated silver ion concentration-dependent effects, while the newly introduced parameters (3D structure and EPS) indicated both silver ion concentration-dependent effects and effects related to the silver species applied.