Combined effect of UV-irradiation and TiO2-nanoparticles on the predator–prey interaction of gammarids and mayfly nymphs

Although nanoparticle production and application increases continuously, their implications in species interactions, especially in combination with other environmental stressors, are rarely assessed. Therefore, the present study investigated the influence of 2 mg/L titanium dioxide nanoparticles (nTiO2; <100 nm) on the interaction between the prey Ephemerella ignita (Ephemeroptera) and the predator Gammarus fossarum (Amphipoda) over 96 h considering UV-irradiation at field relevant levels (approximately 11.4 W/m2) as an additional environmental factor (n = 16). At the same time, gammarid's consumption of an alternative food source, i.e. leaf discs, was assessed. All endpoints covered were not affected by nTiO2 alone, while the combination of nTiO2 and UV caused a reduction in gammarid's predation (68%), leaf consumption (60%) and body weight (22%). These effects were most likely triggered by the UV-induced formation of reactive oxygen species by nTiO2. The present study, hence, highlights the importance to cover UV-irradiation during the risk assessment of nanoparticles. -- Highlights: • nTiO2 alone did not affect gammarids leaf consumption and predation on mayfly. • Ambient UV intensities affected significantly only gammarids leaf consumption. • Irradiation of nTiO2 by UV resulted in strong impact on both organisms. • Environmental factors alter nTiO2 toxicity. -- UV-irradiation influences nanoparticles' ecotoxicity rising concerns about adverse effects in trophic interactions and ecosystem functions