Seasonal assessment of biomarkers in Channa punctata from Tampara Lake, Odisha, India and toxicity of thorium nitrate on fish

Tampara Lake, a freshwater lake in the Chatrapur beach placer deposits of Ganjam, Odisha, India is a well-known tourist attraction. Multiple factors seem to disturb the aquatic life of Tampara Lake, especially fish. Chatrapur beach placers are rich in various heavy minerals including monazite, an ore of thorium, that emits high background radiations and can affect the biota. Run-offs from the monazite mining sites on the beach placers are also presumed to be carried to the lake. Tourism, local transportation, fishing activities, presence of heavy minerals and mining run-offs appear to disrupt the lake's ecosystem. The present work assessed the protein and lipid concentrations in the liver and muscle, nuclear abnormalities in the peripheral blood erythrocytes and histopathology of gills, liver, kidney, intestine and stomach of Channa punctata from Tampara Lake in summer, winter and rainy seasons. The study also documented the effects of thorium nitrate, a byproduct of monazite ore processing, on Channa punctata of non-monazite areas. Channa punctata from the Tampara lake had significantly lower protein and lipid content in the liver and muscle, nuclear deformities and micronuclei in the erythrocytes and deformities in the gill, kidney, liver, stomach and intestine relative to the fish from the non-monazite areas. Seasonal alterations were observed in the protein and lipid content of muscle and liver, gill and kidney structure. Fish from the non-monazite areas treated with sub-lethal concentrations of thorium nitrate showed a dose-dependent response in the protein and lipid content of liver and muscle, erythrocyte nuclear abnormalities and histopathological aberrations. The present study provides evidence that Channa punctata from Tampara Lake have relatively low nutritional value compared to fish from undisturbed non-monazite areas and are probably distressed by the water contamination due to the presence of heavy minerals and anthropogenic interventions.