Due to their widespread use in consumer products an exposure of the aquatic
environment to nanoparticles (NPs) is most likely. Especially metal/metaloxide NPs are
widely used, of which silver nanoparticles (AgNPs) have gained considerable attention
due to their broad microbiocidal properties implying a specific hazard for exposed
aquatic algae and bacteria.In a case study with selected AgNPs (different sizes (10, 20
and 40 nm), and different coatings (citrate coated, non-coated)), the toxicity to natural
freshwater microbial communities was determined. To distinguish between particle
related effects and effects caused by free silver ions silver nitrate (AgNO3) was tested
as a reference. The effects on the algal part of the community was studied through
pigment profiling with HPLC. The bacterial community composition was analysed by
metabolic profiling (ecologplates™). Inhibition of growth detected as a decrease in total
biomass was seen in both bacterial and algal communities, for some cases in the range
of environmentally realistic concentrations. Differences in toxicity could be determined
for the different particles with AgNO3 being for almost all cases the most toxic
compound with one excpetion. All experiments were backed up by analytical
measurements (total silver content, dissolved silver (ultrafiltration), particle size
distribution (Nanosight))
