Effects of LaCoO(3) perovskite nanoparticle on Daphnia magna: accumulation, distribution and biomarker responses

Perovskite nanomaterials (PNMs) have been shown to be promising materials for the effective replacement of conventional energy source materials. With the increasing use of PNMs, they will inevitably enter aquatic environments, giving rise to concerns regarding the environmental impact of PNMs. To fill up the gap in information about the environmental effect of PNMs, Daphnia magna was exposed to a typical PNM LaCoO(3) for 48 h, to assess temporal patterns in PNM bioaccumulation and distribution. Synchrotron radiation based micro X-ray fluorescence spectroscopy (μ-XRF) was used to investigate the time dependent spatial distribution of LaCoO(3). Reactive oxygen species (ROS), superoxide dismutase (SOD) and Na(+)/K(+)-adenosine triphosphatase (ATPase) were measured as key biomarkers. The results showed that oxidative stress was observed at both LaCoO(3) concentrations and Na(+)/K(+)-ATPase was inhibited by high levels of LaCoO(3). The mode of action of LaCoO(3) was mainly dependent on the metal forms. At low LaCoO(3) levels, food ingestion was the main entry pathway into organisms and LaCoO(3) nanoparticle aggregates accumulated in the gut area. At high LaCoO(3) levels, both waterborne and dietary uptake was observed and the gut and thoracic limbs were the main target sites for LaCoO(3) nanoparticle aggregates and dissolved ions, respectively. LaCoO(3) was not found to translocate in daphnids during the 48 h exposure period at either concentration, suggesting that internalization did not occur. These findings help further our understanding of the fate of PNMs in aquatic organisms, as well as the associated biological responses to PNM exposure.