Copper and cadmium, isolated and in the mixture, in Eurytemoraaffinis (Copepoda): effects on the physiology, behavior, and reproduction of organisms exposed via water or via food

Abstract

Anthropogenic activities such as agriculture and industries generate high amounts of harmful residuals, most likely ending in aquatic ecosystems and potentially damaging the whole aquatic food chain. The excess of metals released in the environment is of significant concern since these elements can affect the physiology of different levels of the food chain - e.g., producers (phytoplankton); primary consumers (e.g., zooplankton), and secondary consumers (e.g., fish). Besides their single effects in the organisms, the metals can interact with other metals in the aquatic systems and with other contaminants such as pesticides and microplastics, forming complex mixtures that can be antagonistic, synergistic, or with additive responses. The study of metal mixtures also can be challenging due to the essentiality of some metals (e.g., copper) in metabolic processes. Copepods are part of zooplankton and are present in freshwater, marine, and estuarine environments. They are an essential link between the producers and higher trophic levels. The use of copepods in ecotoxicology is still scarce when compared to other organisms from zooplankton, such as the Cladoceran daphnia sp. Still, its use has been increasing in the last decades and different approaches are being tested, from traditional ecotoxicology to molecular ecotoxicology. In recent years, the euryhaline Calanoida copepod Eurytemora affinis - native from the northern hemisphere - was a relevant test organism in ecotoxicology. This proposal aims to evaluate the physiological and behavioral responses of E. affinis exposed to environmental and realistic concentrations of copper (essential metal) and cadmium (non-essential metal), isolated and in the mixture. The acute tests will be done with the contaminants in the water, while the chronic and sub-chronic tests will be performed with metals present in the water (direct exposure) or the food (indirect exposure). Different stages of the organism will be exposed to the metals. We will evaluate the effects on the filtration and ingestion rates, behavior, egg hatching, nauplii survival, and reproduction. With this approach, we aim to elucidate the most damaging exposure route to the organisms and the effects of these exposures in the long term (multigenerational). In addition, we will be able to compare the responses of this species (euryhaline, from the northern hemisphere) with a freshwater species used by us in our current project in Brazil (freshwater, native from Brazil). (AU)