How much are metals for next-generation clean technologies harmful to aquatic animal health? A study with cobalt and nickel effects in zebrafish (Danio rerio)

Abstract

Cobalt (Co) and nickel (Ni) are key metals for next-generation clean technologies with broad applications in industrial, military and commercial products. However, the knowledge about their environmental impact and toxicity to aquatic organisms remain limited, especially for the early developmental stages of fish. Thus, the current study aimed to evaluate the developmental toxicity of Co and Ni in zebrafish (Danio rerio). Zebrafish embryo-larval toxicity test (ZELT) was conducted with Co and Ni at different concentrations (10, 20, 40, 60, 80 and 100 mg L−1) during 144 h in a static condition. Multiple biomarker responses were analyzed, such as mortality, hatching rate, neurotoxicity, cardiotoxicity, teratogenesis, and morphometric changes. Results showed high embryotoxicity of Ni compared to Co. Both metals inhibited the hatching process and induced morphological changes, such as inhibition of swim bladder inflation, yolk sac edema and pericardial edema. Co induced bradycardia in zebrafish embryos, while Ni caused tachycardia, indicating differential cardiotoxic effects. Overall, the exposure to Co and Ni disrupts early development of zebrafish, confirming their risk to the health of freshwater fish. Results indicated the ZELT as a suitable approach to assess the environmental risk of metals for next-generation clean technologies.