Multi-biomarker assessment of essential and toxic elements accumulation in Labeo gonius from Khushab Lake (Pakistan)

The continuous increase in the concentration of heavy metals in bodies of water due to human activity poses a serious threat to the sustainability and overall health of the ecosystem. This study investigated the essential and toxic elements bioaccumulation in various tissues (gills, muscles, liver, and brain) of the Minor carp (Labeo gonius) from two sampling sites of highly polluted Khushab Lake, a tributary of River Jhelum (in the Pakistan's Punjab province), along with a less exposed reference site (Chashma Lake-less polluted site). The impacts of pollution on the health profile of the fish were assessed using multiple biomarkers for analysis. The maximum accumulation of essential and toxic elements was reported in liver tissues, followed by gills. Copper (Cu) and iron (Fe) were the highest accumulated essential elements in liver and gills tissues, while magnesium (Mg) and calcium (Ca) were the highest accumulated in muscles and brain tissues. Hematological and serum biochemical profile of L. gonius showed intense abnormalities at Khushab Lake as compared to reference site. Histopathological investigations indicated severe alterations in the liver tissues along with significant changes in other tissues. Principal component analysis (PCA) showed strong correlations among essential and toxic elements in various tissues of fish. The results revealed that aquatic life in Lake Khushab is at the greatest risk to its health. Therefore, mitigating measures should be adapted by key stakeholders including environmental protection agency (ensure disposal of pre-treated wastes and effluents) and fisheries department (limnological assessment and stocking of fish at regular intervals).