Physical-chemists, (micro)biologists, and ecologists need to conduct meaningful experiments to study the environmental risk of engineered nanomaterials with access to relevant mechanistic data across several spatial and temporal scales. Indoor aquatic mesocosms (60L) that can be tailored to virtually mimic any ecosystem appear as a particularly well-suited device. Here, this concept is illustrated by a pilot study aimed at assessing the distribution of a CeO2-based nanomaterial within our system at low concentration (1.5 mg/L). Physico-chemical as well as microbiological parameters took two weeks to equilibrate. These parameters were found to be reproducible across the 9-mesocosm setup over a 45-day period of time. Recovery mass balances of 115 ± 18% and 60 ± 30% of the Ce were obtained for the pulse dosing and the chronic dosing, respectively. This demonstrated the relevance of our experimental approach that allows for adequately monitoring the fate and impact of a given nanomaterial.

The CeO2 NPs are increasingly used in industry but the environmental release of these NPs and their subsequent behavior and biological effects are currently unclear. This study evaluates for the first time the effects of CeO2 NPs on the survival and the swimming performance of two cladoceran species, Daphnia similis and Daphnia pulex after 1, 10 and 100 mg.L−1 CeO2 exposures for 48 h. Acute toxicity bioassays were performed to determine EC50 of exposed daphnids. Video-recorded swimming behavior of both daphnids was used to measure swimming speeds after various exposures to aggregated CeO2 NPs. The acute ecotoxicity showed that D. similis is 350 times more sensitive to CeO2 NPs than D. pulex, showing 48-h EC50 of 0.26 mg.L−1 and 91.79 mg.L−1, respectively. Both species interacted with CeO2 NPs (adsorption), but much more strongly in the case of D. similis. Swimming velocities (SV) were differently and significantly affected by CeO2 NPs for both species. A 48-h exposure to 1 mg.L−1 induced a decrease of 30% and 40% of the SV in D. pulex and D. similis, respectively. However at higher concentrations, the SV of D. similis was more impacted (60% off for 10 mg.L−1 and 100 mg.L−1) than the one of D. pulex. These interspecific toxic effects of CeO2 NPs are explained by morphological variations such as the presence of reliefs on the cuticle and a longer distal spine in D. similis acting as traps for the CeO2 aggregates. In addition, D. similis has a mean SV double that of D. pulex and thus initially collides with twice more NPs aggregates. The ecotoxicological consequences on the behavior and physiology of a CeO2 NPs exposure in daphnids are discussed.

Mesocosms are an invaluable tool for addressing the complex issue of exposure during nanoecotoxicological testing. This experimental strategy was used to take into account parameters as the interactions between the NPs and naturally occurring (in)organic colloids (heteroaggregation), or the flux between compartments of the ecosystems (aqueous phase, sediments, biota) when assessing the impacts of CeO2 NPs in aquatic ecosystems. In this study, we determine the transfer, redox transformation, and impacts of 1 mg L(-1) of bare and citrate coated CeO2-NPs toward an ecologically relevant organism (snail, Planorbarius corneus) exposed 4 weeks in a complex experimental system mimicking a pond ecosystem. Over time, CeO2-NPs tend to homo- and heteroaggregate and to accumulate on the surficial sediment. The kinetic of settling down was coating-dependent and related to the coating degradation. After 4 weeks, Ce was observed in the digestive gland of benthic organisms and associated with 65-80% of Ce(IV) reduction into Ce(III) for both bare and coated CeO2 NPs. A transitory oxidative stress was observed for bare CeO2-NPs. Coated-NPs exposed snails did not undergo any lipid peroxidation nor change in the antioxidant contents, while Ce content and reduction in the digestive gland were identical to bare CeO2-NPs. We hypothesized that the presence of citrate coating enhanced the defense capacity of the cells toward the oxidative stress induced by the CeO2 core.

International audienceIndoor aquatic mesocosms were designed to mimic pond ecosystems contaminated by a continuous point-source discharge of cerium oxide nanoparticles (CeO2-NPs). Bare and citrate-coated CeO2-NPs exhibited different chemical and colloidal behaviors in the aquatic mesocosms. Bare CeO2-NPs were chemically stable but quickly homo-aggregated and settled out of the water column. Citrate-coated NPs both homo-and hetero-aggregated but only after the several days required to degrade the citrate coating. While they were more stable as a colloidal suspension, coated CeO2-NPs dissolved faster due to surface complexation with citrate, which resulted in the release of dissolved Ce into the water column. The different distributions over time between water/sediment or dissolved/particulate forms of Ce controlled the availability of Ce to benthic grazers (mollusk Planorbarius corneus) and planktonic filter feeders (copepod Eudiaptomus vulgaris)

Two years after the beginning of the interventions, both eradication operations are still ongoing. Biosecurity measures have been implemented to reduce reinvasion risks of both taxa. With the long-term monitoring of various native plants and animals, Bagaud Island will become a reference study site for scientific purposes.

Indoor aquatic mesocosms were used to assess the behavior of fragmented products of a wood stain containing CuO nanoparticles in a simulated pond ecosytem for 1 month. Byproducts of degradation containing Cu are likely to be released during the use and end-of-life of this wood stain. Over two months, a pond ecosystem was mimicked in 60 L tanks and exposed in environmentally relevant conditions to fragmented products of CuO nanoparticle-based wood stain or pristine CuO nanoparticles. Cu (bio)transformation and (bio)distribution within different environmental compartments (e.g. water, sediments, benthic grazers) were carefully analyzed. Because of the presence of the stain matrix, CuO nanoparticles contained in fragmented products were less bio-physical-chemically transformed (dissolution, complexation) with respect to pristine nanoparticles. After 28 days, only 1% of the Cu injected following fragmented product exposure remained in the water column (0.08 µg.L -1 ), against 10% for the pristine CuO nanoparticles (2.67 µg.L -1 ). Among these ~10%, ~51% were dissolved Cu species (1.35 µg.L -1 ). These results are discussed with respect to the ecological compartments in which they accumulated, and to the dose to which aquatic organisms with distinct life traits were exposed.

Silver nanomaterials with different shapes (spheres, plates, wires, rods, cubes) are valued by industries and scientists for their shape-dependent properties which make them useful for diverse applications.

Production of Manufactured Nanomaterials (MNMs) has increased extensively due to economic interest in the current years. However, this widespread use raises concern about their impact on human and environment. Current efforts are made, both at national and international levels to help developing safer MNMs in the market. In order to assess hazards of MNMs, it is important to take into account exposome parameters in order to link fate and behavior of MNMs to their potential toxicity. In that context, the aim of this study was to compare exposure and impact of TiO 2 MNMs-based cement at different levels of its life cycle (TiO 2 MNMs, cement containing TiO 2 MNMs) between two exposure mesocosm scenarios mimicking : marine conditions using the bivalve Scrobicularia plana and freshwater conditions using the gastropod Planorbarius corneus, for 28 days. These approaches allows measurements of physical-chemical parameters throughout the duration of the exposure. Similar results were observed in both exposure conditions since in the two scenarios Ti was removed from the water column and accumulated in surficial sediments. While in P. corneus, statistically different concentrations of Ti were measured in the digestive glands compared to controls following exposure to TiO 2 MNMs, elevated background of Ti concentrations were measured in the controls of S. plana that did not allow to discriminating any bioaccumulation process. In addition, both TiO 2 MNMs and TiO 2 MNM-based cement exposed S. plana did not present any activation of the p38 mitogen-activated protein kinase (MAPKs).This study demonstrates the challenge of using freshwater-marine continuum using a mesocosm approach in nanosafety.