Lethal and sublethal toxicity of ytterbium in rainbow trout juveniles.

The heavy rare earth element ytterbium (Yb) is a critical element of technology finding its way into urban wastewaters from solid waste disposal sites. The purpose of this study was to investigate the lethal and sublethal toxicity of Yb to rainbow trout juveniles. They were exposed to increasing concentrations of Yb (0.06-40 mg/L) for 96 h at 15 °C. Mortality was recorded, and in the surviving fish, the following biomarkers were determined: protein aggregation, thioneins, lipid peroxidation (LPO), and DNA damage in gills and the liver. The 96-h lethal concentration (LC50) was 2.7 ± 0.66 mg/L indicating that this element is toxic to fish. Biomarker responses to Yb occurred at concentration 45 times less than the LC50 in some cases. The following biomarkers were positively (p < 0.05) correlated to fish survival: liver thioneins, gill DNA strand breaks, LPO, and protein aggregation in the liver. The decrease in LPO in the liver and gills by Yb suggests reduced production of reactive oxygen species production. In conclusion, Yb is toxic to trout juveniles producing sublethal effects at concentrations range of 60 µg/L after 96 h. This concentration represents an upper limit for consideration for aquatic animal health.