Carotenoid-Rich Fungal Pigment from Fusarium tricinctum Mitigates Heavy Metal-Induced Toxicity in Daphnia magna.

Heavy metals induce toxicity in aquatic organisms through bioaccumulation and oxidative stress. This study investigated the protective potential of a carotenoid-rich fungal pigment from Fusarium tricinctum against cadmium, zinc, chromium, mercury, and copper toxicity in Daphnia magna. HPLC and UV-Vis analyses identified β-carotene as the predominant carotenoid, while the pigment exhibited strong DPPH radical-scavenging activity. Acute toxicity assays determined 48-h LC₅₀ values, and a concentration of 10 µg/L was selected for subsequent co-exposure experiments. ICP-MS analysis revealed that the fungal pigment significantly reduced tissue accumulation of all tested heavy metals compared with metal-only treatments. Moreover, pigment co-exposure attenuated oxidative stress by reducing malondialdehyde levels and modulating antioxidant responses, including SOD, CAT, and GSH. Overall, the F. tricinctum carotenoid pigment enhanced D. magna survival and alleviated heavy metal-induced oxidative damage, demonstrating its potential as a natural protective agent against metal stress in aquatic ecosystems.