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Effects of silver nanoparticles on food chains and environmental processes

 

Silver nanoparticles are often used in commercial or medical products due to their anti-microbial effect and can end up in the environment. This project has investigated the influence of nanoparticles on different aquatic microbial communities.

Background (completed research project)

Silver has a toxic effect on bacteria, but is harmless for humans. The combination of these properties turn silver nanoparticles into nanomaterials that are often used in commercial products and medicine. Silver nanoparticles end up in the environment through wastewater when using these products. Their anti-microbial effect represents a risk there for living organisms, mostly micro-organisms. Renata Behra and her team investigated the effects of silver nanoparticles on two different biofilms, which depend on a healthy microbial community. The first system is dominated by foliage-disintegrating fungus, which interact with bacteria. The second system is composed of algae and other microorganisms. Both communities produce a considerable amount of biomass, off which further aquatic organisms feed, such as shrimps and snails. The project investigated the effects of silver nanoparticles on ecological functions in which these two systems are involved. It further analysed whether silver nanoparticles influence the coexistence between bacteria and fungus or algae and to what extent the silver nanoparticles pass into larger, more complex organisms through the food chain. Finally, Renata Behra and her team also investigated the effects of the sulphidation of silver nanoparticles on biofilms. These experiments are based on the findings of Ralf Kaegi’s NFP 64 project, which showed that silver nanoparticles react very quickly with sulphides in wastewater.

Results

The investigations have shown that the silver nanoparticles impair different ecological processes as well as species composition in both biofilms. The particles accumulated in biofilms and were absorbed by shrimps and snails, affecting their behaviour and reproduction. This confirms the role of biofilms as an important entrance gate of nanoparticles into the food chain and shows that silver nanoparticles have both a direct and indirect effect on aquatic ecosystems. Some of these effects could not be observed in the experiments with dissolved silver and thereby can be specifically traced back to nanoparticles. Furthermore, Renata Behara’s team could demonstrate that silver nanoparticles that agglomerate with sulphides have no toxic effects on biofilms, thereby confirming the findings from Ralf Kaegi’s project: the sulphidation of silver nanoparticles in wastewater represents an important process that significantly reduces the toxicity of silver nanoparticles.

Relevance

This project presents methods to investigate the influence of nanoparticles on different ecosystems and shows important ways by which silver nanoparticles can pass into the food chains via microorganisms and thus how they can have an indirect effect on ecosystems.

Original title

Silver nanoparticle effects on simple stream food webs and ecosystem processes

Project leader(s)

  • Dr. Renata Behra

Co-applicants

  • Dr. Ralf Kägi
  • Dr. Andreas Voegelin

 

 

Further information on this content

 Contact

Dr. Renata Behra Umwelttoxikologie UTOX
EAWAG
Überlandstrasse 133
Postfach 611
8600 Dübendorf +41 44 823 51 72 renata.behra@eawag.ch