Algal Foods Reduce the Uptake of Hematite Nanoparticles by Downregulating Water Filtration in Daphnia magna.

Abstract

Rapid developments in nanotechnology have led to the release of substantial amounts of nanoparticles (NPs) into aquatic environments, where many types of biotic particles are present and could potentially interact with the NPs. Nevertheless, how biotic particles may affect the bioaccumulation and toxicity of NPs remains largely unknown. In the present study, we investigated the effects of the green alga Chlamydomonas reinhardtii on the accumulation kinetics (uptake, assimilation, efflux) and toxicity of polyacrylate-coated hematite NPs (HemNPs), using Daphnia magna as the test organism. As a biotic particle and daphnid food, C. reinhardtii reduced the accumulation and toxicity of HemNPs in D. magna. The HemNPs were well-dispersed with little adsorption to the alga. Their decreased accumulation could thus be partly explained by their low trophic transfer from the alga to the daphnid and by the inductive effects of the alga on HemNP efflux. However, the main cause was the direct inhibition of HemNP uptake from the water phase as a result of the reduced water-filtration activity of D. magna in the presence of C. reinhardtii. Overall, in bioaccumulation studies, the inhibitory effects of biotic particles on NP uptake from the water phase should be paid attention.