Can photocatalytic and magnetic nanoparticles be a threat to aquatic detrital food webs?

Arunava Pradhan,Marta Fernandes,Pedro M Martins,Cláudia Pascoal,Senentxu Lanceros-Méndez,Fernanda Cássio

doi:10.1016/j.scitotenv.2020.144576

Abstract

Freshwaters are likely to serve as reservoirs for engineered nanomaterials (ENMs) due to their accelerated unintentional release, increasing the relevance of assessing their impacts on aquatic biota and the ecosystem processes they drive. Stream-dwelling microbes, particularly fungi, and invertebrate shredders play an essential role in the decomposition of organic matter and transfer of energy to higher trophic levels. We assessed the impacts of two photocatalytic (nano-TiO2 and erbium doped nano-TiO2) and one magnetic (nano-CoFe2O4) ENMs on detrital-based food webs in freshwaters by exposing chestnut leaves, colonized by stream-dwelling microbes, to a series of concentrations (0.25–150 mg L−1) of these ENMs. Microbial decomposition and biomass of fungal communities, associated with leaves, were not affected by the ENMs. However, the activities of antioxidant enzymes of microbial decomposers were significantly (P < 0.05) stimulated by ENMs in a concentration-dependent way, suggesting oxidative stress in stream microbial communities. The stronger responses of these stress biomarkers against nano-TiO2 (increase upto 837.5% for catalase, 1546.8% for glutathione peroxidase and 1154.6% for glutathione S-transferase) suggest a higher toxicity of this ENM comparing to the others. To determine whether the effects could be transferred across trophic levels, the invertebrate shredder Sericostoma sp. was exposed to ENMs (1 and 50 mg L−1) for 5 days either via contaminated water or contaminated food (leaf litter). Leaf consumption rate by shredders decreased significantly (P < 0.05) with increasing concentrations of ENMs via food or water; the effects were more pronounced when exposure occurred via contaminated food (up to 99.3%, 90.7% and 90.3% inhibition by nano-Er:TiO2, nano-CoFe2O4 and nano-TiO2, respectively). Overall, the tested photocatalytic and magnetic ENMs can be harmful to microbial decomposers and invertebrate shredders further compromising detrital-based food webs in streams.

Highlights

Recent developments in nanotechnology led to an increased worldwide production and application of engineered nanomaterials (ENMs) (Stark et al 2015)
The current study aims to evaluate the effects of nano-TiO2, nano-Er:TiO2 and nano-CoFe2O4 on stream microbial decomposer communities and invertebrate shredders using the detrital model system, which has proven sensitive to various contaminants (Pradhan et al 2011; Pradhan et al 2015a; Tlili et al 2016)
The DLS revealed that the average hydrodynamic diameter (HDD) of the nano-TiO2 and nano-Er:TiO2 were 222.1 ± 4 nm and

Summary

Introduction

Recent developments in nanotechnology led to an increased worldwide production and application of engineered nanomaterials (ENMs) (Stark et al 2015). Commission, 2016), which may further enhance the commercial use of these ENMs in Europe. Nanoparticles of TiO2 are often applied in wastewater effluent treatments and chlorine-free disinfection due to their photocatalytic properties (Rickerby 2014). Nano-TiO2, doped with rare earth metals, like erbium (nano-Er:TiO2), can enhance the photocatalytic performance because of the vacant f-orbitals of Er3+ that allow intermediate energy states (reducing the band gap), improving the adsorption of various molecules (e.g. amines, alcohols, aldehydes, amines thiols) from contaminants onto the nanoparticle surface (Gomez et al 2012; Martins et al 2014). Nanoparticles of CoFe2O4 have potential to remove anionic dyes (Yavari et al 2016) and to treat metal-rich industrial effluents or wastewaters (Srivastava et al 2016)

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