Toxicity of CeO₂nanoparticles on a freshwater experimental trophic chain: A study in environmentally relevant conditions through the use of mesocosms

Abstract

The toxicity of CeO2 NPs on an experimental freshwater ecosystem was studied in mesocosm, with a focus being placed on the higher trophic level, i.e. the carnivorous amphibian species Pleurodeles waltl. The system comprised species at three trophic levels: (i) bacteria, fungi and diatoms, (ii) Chironomus riparius larvae as primary consumers and (iii) Pleurodeles larvae as secondary consumers. NP contamination consisted of repeated additions of CeO2 NPs over 4 weeks, to obtain a final concentration of 1 mg/L. NPs were found to settle and accumulate in the sediment. No effects were observed on litter decomposition or associated fungal biomass. Changes in bacterial communities were observed from the third week of NP contamination. Morphological changes in CeO2 NPs were observed at the end of the experiment. No toxicity was recorded in chironomids, despite substantial NP accumulation (265.8 ± 14.1 mg Ce/kg). Mortality (35.3 ± 6.8%) and a mean Ce concentration of 13.5 ± 3.9 mg/kg were reported for Pleurodeles. Parallel experiments were performed on Pleurodeles to determine toxicity pathways: no toxicity was observed by direct or dietary exposures, although Ce concentrations almost reached 100 mg/kg. In view of these results, various toxicity mechanisms are proposed and discussed. The toxicity observed on Pleurodeles in mesocosm may be indirect, due to microorganism's interaction with CeO2 NPs, or NP dissolution could have occurred in mesocosm due to the structural complexity of the biological environment, resulting in toxicity to Pleurodeles. This study strongly supports the importance of ecotoxicological assessment of NPs under environmentally relevant conditions, using complex biological systems.

Effects of nanoparticles in fresh waters: risks, mechanisms and interactions

“…Moreover, Zhu et al . () demonstrated a transfer of nTiO 2 from daphnids to fish but found no biomagnification in higher trophic levels (see also Holbrook et al ., ; Bour et al ., ; Fig. ).…”

Nanomaterials in the environment: Behavior, fate, bioavailability, and effects—An updated review

“…These studies showed that elevated total metal concentrations may also be found in primary producers and aquatic invertebrates (Lowry et al ), but whether or not this represents a hazard by food‐chain transfer or simply exposure due to particle settling/direct exposure is not clear. In other work, Bour et al (, ) serially dosed a freshwater mesocosm with CeO 2 NMs over 4 wk and detected total Ce in the biofilms of primary producers (bacteria, fungi, etc. ), the grazing chironomid larvae, and Pleurodeles larvae (amphibian tadpole) as the top predator in the experiment.…”

“…In the last decade, there have been numerous reviews on the ecotoxicity of NMs (Handy et al 2008a(Handy et al , 2012a(Handy et al , 2012bKlaine et al 2008;Kahru and Dubourguier 2010;Fabrega et al 2011;Levard et al 2012;Schultz et al 2014;Adam et al 2015;Bour et al 2016aBour et al , 2016bGarner et al 2015;Semenzin et al 2015;Hjorth et al 2017a). A number of systematic reviews have discussed ecotoxicity databases and the quality and regulatory adequacy of the data therein (Hartmann et al 2017;Hjorth et al 2017b).…”

Cerium(iv) oxide nanoparticles induce sublethal changes in honeybees after chronic exposure

“…For example, Tourinho and co-authors reported that 4 weeks' exposure to nCeO 2 -spiked Lufa 2.2 soil (10-1000 mg kg −1 dry soil) had no effects on the survival and reproduction of springtails (Folsomia candida). 22 No toxicity was recorded in Chironomus riparius larvae, despite substantial Ce accumulation in this organism after exposure to 1 mg L −1 nCeO 2 in experimental freshwater ecosystem studies; 23,24 only differences in teratogenicity were observed between treatments. 24 Alaraby et al showed both up-and downregulation of selected Hsp genes, internalisation of nCeO 2 in the gut epithelium and its presence in haemocytes of fruit fly (Drosophila melanogaster) larvae after exposure to nCeO 2 applied in culture medium (0.01-10 mM, equivalent to 1.72-1721.1 mg L −1 ).…”