Environmental Impacts of CoWO4 and NiWO4 Nanoparticles on Trophic Levels of an Aquatic Food Chain

Abstract

The increasing production and use of nanoparticles (NPs; < 100 nm) of cobalt tungstate (CoWO4) and nickel tungstate (NiWO4) in environmental and technological areas contributes to the presence of these contaminants in aquatic ecosystems. Although several studies report the toxicity of NPs to aquatic biota, the toxic potential of CoWO4 and NiWO4 on freshwater organisms is still unknown. In light of this, the aim of this research is to evaluate the effects and mechanisms of toxicity, via multiple parameters, of CoWO4 and NiWO4 NPs on three trophic levels of a planktonic food chain, composed by the chlorophycean Raphidocelis subcapitata (primary producer), the cladoceran Ceriodaphnia silvestri (primary consumer) and the fish Hyphessobrycon eques (secondary consumer). These Neotropical species will be exposed to different concentrations of the NPs in order to determine the toxicity of these materials to the test organisms by assessing population, morphological, biochemical, physiological/metabolic and reproductive parameters. In addition, microcrustaceans will be exposed by two routes, medium and contaminated food, which will allow investigation of bioaccumulation and transfer of NPs in this food chain. The evaluated species make up the base of aquatic food chains and contact of organisms with the NPs can be bioaccumulated and consequently transferred to the food chains. Therefore, any damage to these trophic levels can have consequences throughout the aquatic trophic web, causing imbalance throughout the ecosystem. With this study, it is expected to determine the main toxicity mechanisms responsible for possible deleterious effects of CoWO4 and NiWO4 NPs on microalgae, cladocerans and fish, from a complete and integrated approach, which includes the risk assessment of cobalt and nickel NPs in tropical freshwater bodies by obtaining reference values that will allow the risk of these NPs to be quantitatively characterized, in order to provide valuable information that may subsidize regulatory actions aimed at protecting aquatic biota.