N. O. ERHUNMWUNSE

Heavy metal contamination poses significant ecological and health risks in aquatic ecosystems due to its persistence and bioaccumulation potential. This study assesses heavy metal contamination in Brycinus macrolepidotus from the Ovia River, Nigeria, using non-invasive techniques. Iron (Fe), zinc (Zn), copper (Cu), lead (Pb), and cadmium (Cd) levels were examined in muscle tissues, caudal fins, and scales. The research begins with an in-depth background study emphasizing the
environmental and health implications of heavy metal contamination. Non-invasive techniques are prioritized to accurately assess contamination levels while minimizing harm to fish populations. Ovia River, chosen for its freshwater ecosystem supporting diverse aquatic life and human activities, serves as the study area, with sampling locations representing both upstream and downstream conditions affected by various human activities. Sample collection involved careful handling of Brycinus macrolepidotus specimens to preserve their physiological state. Noninvasive methods collected muscle tissue, caudal fin clips, and scales for heavy metal analysis, ensuring minimal harm to the fish. Results reveal varying heavy metal concentrations, predominantly iron and zinc, in different fish tissues. Non-invasive techniques effectively assessed contamination levels, providing insights crucial for environmental monitoring and conservation efforts.

6PPD-quinone (6PPD-Q), a transformation product of tire antioxidants, has recently emerged as a potent aquatic contaminant with significant toxicological implications. This study investigated the sublethal effects of 6PPD-quinone (6PPD-Q) on lipid metabolism in Clarias gariepinus juveniles over a 28-day exposure. Fish were exposed to 500, 1000, and 1500 μg/L of 6PPD-Q, with positive and negative controls, following OECD (2019) guidelines. Lipid profile parameters total cholesterol (TC), triglycerides (TG), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), and very-low-density lipoprotein cholesterol (VLDL-C) were analyzed to assess hepatotoxic and oxidative effects. Results (P <0.05) showed significant increases in TC and LDL-C, with concurrent reductions inHLDL-C and VLDL-C at higher concentrations, indicating oxidative stress and lipid dysregulation. Triglycerides exhibited an initial rise followed by depletion at the highest dose, suggesting disrupted β-oxidation. further mechanistic studies are recommended to elucidate the biochemical and molecular pathways affected by 6PPD-Q exposure.In conclusion, chronic 6PPD-Q exposure induced lipid imbalance and hepatocellular stress in C. gariepinus, underscoring the toxic potential of tire-derived pollutants in freshwater ecosystems