Gadolinium exposure in Procambarus clarkii: tissue-specific bioaccumulation and oxidative stress responses

Gadolinium (Gd), a rare earth element widely used in medical imaging and industry, is increasingly detected in aquatic environments. This study examines tissue-specific bioaccumulation and antioxidant responses in Procambarus clarkii following exposure to environmentally relevant Gd concentrations (0.1, 1, 10, and 100 μg/L) over 14 days. Bioaccumulation was evident in the gills and hepatopancreas at higher exposure levels (10 and 100 μg/L), whereas muscle concentrations remained below the limit of quantification. Oxidative stress responses varied by tissue, with no clear trend revealed by the non-metric multidimensional scaling (NMDs), suggesting limited antioxidant activation likely due to low Gd accumulation and short exposure duration. However, superoxide dismutase (SOD) activity significantly increased in the gills and hepatopancreas at higher Gd concentrations. In contrast, glutathione peroxidase (GPx) activity showed inconsistent trends, while glutathione S-transferase (GST) activity was elevated in hepatppancreas and muscle only at 0.1 μg/L. Lipid peroxidation was most pronounced in the gills. The Integrative Biomarker Response-Threshold (IBR-T) index revealed low-dose effects consistent with hormetic responses, highlighting biologically relevant alterations observed at the lowest Gd concentrations. These findings suggest that P. clarkii exhibits tissue-specific Gd bioaccumulation and oxidative stress responses, albeit with variable biomarker activation. Further research is needed to assess the long-term effects of Gd exposure in freshwater crustaceans, particularly given rising anthropogenic Gd inputs.