Effects and Implications of Trophic Transfer and Accumulation of CeO₂ Nanoparticles in a Marine Mussel

Abstract

Bivalves are hypothesized to be key organisms in the fate and transport of engineered nanomaterials (ENMs) in aquatic environments due to their ability to filter and concentrate particles from water, but how different exposure pathways influence their interactions with ENMs is not well understood. In a five-week experiment, we tested how interactions between CeO 2 ENMs and a marine mussel, Mytilus galloprovincialis, are affected through two exposure methods, direct and through sorption to phytoplankton. We found that phytoplankton sorbed ENMs in <1 h. The exposure methods used did not result in significantly different mussel tissue or pseudofeces Ce concentrations. Approximately 99% of CeO 2 was captured and excreted in pseudofeces and average pseudofeces mass doubled in response to CeO 2 exposure. Final mean dry tissue Ce concentration (±SE) for treatments exposed to 3 mg L −1 CeO 2 directly was 33 ± 9 μg g −1 Ce, and 0 ± 0, 19 ± 4, 21 ± 3, and 28 ± 5 μg g −1 for treatments exposed to 0, 1, 2, and 3 mg L −1 CeO 2 sorbed to phytoplankton. Clearance rates increased with CeO 2 concentration but decreased over time in groups exposed to CeO 2 directly, indicating stress. These results show the feedback between ENM toxicity and transport and the likelihood of biological mediation in the fate and transport of ENMs in aquatic environments.

Heteroaggregation of nanoparticles with biocolloids and geocolloids

“…This study showed that heteroaggregation between NPs and cells can have important impacts on the two components that lead to toxicity in E. coli RR1, and significant reduction of CeO 2 NPs to Ce(III) [107]. Similarly, Conway et al [120] reported that sorption of CeO 2 NPs to Isochrysis galbana, a marine phytoplankton, occurred within 1 h but toxicity was not observed until after 7 d.…”

“…Listed in decreasing order of interactions, with zeta potential of each NP in water (pH 5.6) added in parenthesis, they found that CeO 2 NPs (32.2 mV) ≈ TiO 2 NPs (32.7 mV) N ZnO NPs (16.0 mV) N Ag-PVP NPs (− 12.0 mV) N CeO 2 -citrate NPs (−17.9 mV) N Ag-gum Arabic NPs (−27.5 mV) [94]. Heteroaggregation between CeO 2 NPs and Isochrysis galbana was found to increase with NPs concentration [120], and the effect of NP size on heteroaggregation with E. coli has also been described [122]. In the study, Morones and others observed that Ag NPs with diameter of 5±2 nm were preferentially in direct interaction with bacteria, which corresponds to the lower end of size distribution of the Ag NPs cells were exposed to (diameter = 16±8 nm).…”

“…For instance, NPs-microorganism heteroaggregation can lead to increased removal of NPs from wastewater during secondary treatment [106,[115][116][117][118]. Interactions between cell walls of microorganisms and NPs are also thought to precede uptake and toxicity [107,108,[110][111][112]116,119], and may be important for trophic transfer of NPs in both aquatic and terrestrial environments [108,[119][120][121].…”

“…Heteroaggregation between NPs and cells occur rapidly [110,120,126], and heteroaggregates may continue to grow over time if conditions are favorable [126]. Heteroaggregation may be due to weak physical interactions via DLVO and non-DLVO forces [114] as disaggregation (desorption) has been reported in aqueous conditions that may not affect strong chemical bonds.…”

Environmental release, fate and ecotoxicological effects of manufactured ceria nanomaterials

“…The effect of the exposure methods, direct and through sorption to phytoplankton was tested on the mussel Mytilus galloprovincialis. 101 Ce uptake was enhanced by the ingestion via the phytoplankton in the first 5 days of exposure but was similar to a direct exposure after 2 weeks. The authors showed that with increasing nanoceria concentration, mussels increased their clearance rates as well as the pseudofeces production in order to prevent the ingestion of nanoceria.…”