Gammarus fossarum (Crustacea, Amphipoda) as a model organism to study the effects of silver nanoparticles

Abstract Amphipods are one of the most important components of freshwater ecosystems. Among them, gammarids are the most widespread group in Europe and are often used as bioindicators and model organisms in ecotoxicology. However, their use, especially of Gammarus fossarum for the study of the environmental impact of nanoparticles, has been rather limited so far. G . fossarum was selected to assess effects of well-characterized chemically synthesized silver nanoparticles (AgNPs 20 nm and 200 nm) and “green” laboratory synthetized (from plant leaf extracts) AgNPs (AgNPs 23 nm and 27 nm). AgNO 3 was used as a positive control to compare AgNPs effects and silver ions effects. A multibiomarker approach was used to investigate the sub-lethal effects of AgNPs on physiological and behavioural responses of G . fossarum . Two different experiments were carried out. In a preliminary experiment, two populations of G . fossarum ( G . f1 and G . f2 ) were tested for sensitivity differences and the most sensitive one was exposed, in a final experiment, to sub-lethal concentrations of AgNO 3 and the most toxic AgNPs. AgNO 3 and AgNPs 23 nm led to a significant decrease in survival rates, osmoregulation and locomotor activity. Ag internalisation, performed with Secondary Ion Mass Spectrometry (SIMS), showed the presence of silver in gills of G . f2 exposed to AgNPs 23 and 27 nm. This study highlighted the influence of method of synthesis on ion release, uptake and toxic effects of AgNPs on G . fossarum . Osmoregulation appeared to be an effective biomarker indicating the physiological health status of G . fossarum . Locomotor activity, which was the most impacted response, reflects the potential effects of released ions from AgNPs 23 nm at the population level as locomotion is necessary for foraging, finding mates and escaping from predators. Therefore, we propose G . fossarum as a suitable model for environmental nanotoxicology, providing information both at individual and population levels.