Biomonitoring of lead and cadmium pollution using Oreochromis niloticus physiological stress responses

BACKGROUND AND OBJECTIVES: Heavy metal pollution is a major environmental problem because these contaminants are toxic, persistent, and able to accumulate in aquatic ecosystems. Lead and cadmium are among the most hazardous heavy metals due to their toxicity and potential bioaccumulation. The study objectives were to evaluate lead and cadmium contamination in water, sediment, and Oreochromis niloticus. As well as assess hematological and histopathological responses as biomarkers of heavy metal pollution from the downstream Brantas River, Indonesia. METHODS: Water, sediment, gill, and liver samples of Oreochromis niloticus were collected from five sampling stations along the Jagir River. The concentration of lead and cadmium was determined using Atomic Absorption Spectrophotometry. Hematological and histopathological responses were assessed as biomarkers of heavy metal exposure. Statistical differences between stations were evaluated using analysis of variance followed by the least significant difference test. Meanwhile, principal component analysis was used to be applied to examine multivariate relationships among variables. FINDINGS: Heavy metal accumulation increased toward downstream stations, with the highest lead concentration recorded at Station 5. Increased metal accumulation was associated with decreases in erythrocytes count (24.3 percent), hematocrit value (31.7 percent), hemoglobin concentration (26.5 percent), and lymphocyte percentage (25.4 percent). In contrast, leukocyte increased by 14.8 percent, neutrophil by 53.4 percent, and micronuclei by 40.0 percent, indicating physiological stress and genotoxic effects. Histopathological alterations became progressively more severe with increasing contamination levels and included hyperplasia, lamellar fusion, edema, necrosis, hepatocyte degeneration, and hemorrhage. These findings demonstrate a strong relationship between heavy metal accumulation and biological responses in Oreochromis niloticus. CONCLUSION: Histopathological changes became more severe with increasing contamination levels and included hyperplasia, lamellar fusion, edema, necrosis, hepatocyte degeneration, and hemorrhage. These findings indicate that hematological and histopathological changes in Oreochromis niloticus are sensitive biomarkers and can function as biomonitoring tools capable of detecting heavy metal pollution in aquatic ecosystems.