Exposure to neodymium blunts the hypoxic ventilatory response in fathead minnows (Pimephales promelas)

Abstract

In hypoxia, the initial response in vertebrates is hyperventilation, known as the Hypoxic Ventilatory Response (HVR), which is a physiological reflex that allows fish to maintain adequate oxygen uptake. The severity of hypoxia in aquatic ecosystems is growing due to anthropogenic impacts. This is a concern with the recent evidence that metals can affect the ability of fishes to mount the HVR, potentially impacting survival. As Rare Earth Elements (REEs) increase in demand with the shift to a low-carbon economy, there is a critical need to understand their environmental consequences. Neodymium (Nd) is used in green technology and is one of the most critical REEs. Here, we investigate whether exposure to Nd will blunt the HVR in a toxicological model, the fathead minnow (Pimephales promelas). The fathead minnow will be exposed to hypoxia and Nd, and the ventilation rate will be observed and compared to controls to determine if there is a blunt in the HVR when the fish are exposed to both hypoxia and Nd. Nd caused a 31% decrease in the HVR and Nd accumulation in the gills was below the detection limit (LOD: 0.0681 μg/L). Toxicity testing with REEs during this time of economic growth is imperative for the protection of aquatic life in Canada.