Integrated Use of Nanomechanical, Histological, and Biochemical Biomarkers of Oreochromis niloticus as Signs of Metal Stress

Abstract

The bioaccumulation of heavy metals in fish is a recognized environmental problem. Heavy metals, after leaking into the water, penetrate fish directly through the gill and later the skin. Fish develops protective defense mechanisms against the damaging effects of heavy metals. The present investigation aimed to determine the magnitude of five heavy metals (cadmium, iron, manganese, cobalt, and lead) in the muscle tissues of the Nile tilapia (Oreochromis niloticus) and their possible impacts on its histological, nanomechanical, and biochemical biomarkers. The results showed that fish muscle from the polluted site accumulated high levels of the tested heavy metals compared to the reference site. Biochemical profile of the Nile tilapia showed elevated serum glucose, total proteins, uric acid, creatinine, bilirubin, superoxide dismutase, and malondialdehyde in exposed fish compared to their conspecifics at reference site. Histological examination of the liver showed severe alterations in the hepatic tissues. Nanomechanical properties, signified by roughness and stiffness, confirmed the damaging effect of metals on hepatocytes. These findings provide a rational application of histological, nanomechanical and biochemical parameters to be used as indicators of metal stress in aquatic organisms. Therefore, it can be suggested that integrated biomarker response is a comprehensive index of all biomarkers and a good indicator of the health status of aquatic ecosystem and have proven to be very useful in the environmental pollution monitoring.