Antioxidants, immunotoxicological, and histopathological impacts of polypropylene microplastics emitted from paper cups on Clarias gariepinus and the ameliorating role of Spirulina and recovery

Fish are particularly vulnerable to microplastics (MPs), especially polypropylene microplastics (PP-MPs), which are widely used and environmentally persistent. Despite their prevalence, little is known about their impact on fish immune systems. Thus, this study's goal was to look at the antioxidants, immunotoxicological, and histopathological impact of PP-MPs on African catfish Clarias gariepinus and the ameliorating role of Spirulina and recovery. A total of 108 fish, weighing 125 ± 3 g and 27 ± 2 cm, were acclimated and divided into six experimental groups (in triplicate): control, PP-MPs-treated groups (0.14 and 0.28 mg/L), PP-MPs + Spirulina (200 mg/L), and Spirulina alone. Fish were exposed to treatments for 15 days, followed by a 45-day recovery period. Antioxidant enzymes (SOD, CAT, GST, MAD), immune biomarkers, and histopathological changes in the spleen and head kidney were assessed. PP-MPs exposure led to a significant (p < .05) decline in antioxidant enzymes and immune biomarkers compared to controls, with increased melanomacrophage centers and tissue damage. Spirulina supplementation significantly improved immune and antioxidant responses, although some parameters, like MAD and histopathological alterations, showed incomplete recovery even after 45 days. PP-MPs have immunotoxic and oxidative effects on Clarias gariepinus, with partial recovery possible through Spirulina supplementation. However, full restoration of immune tissue morphology requires longer recovery periods. The observed immune alterations were closely associated with histopathological damage in key immune organs.