Assessing water quality of River Mahananda, Malda, India using Cirrhinus reba as a bioindicator: Oxidative stress biomarkers and histopathological fingerprints

Environmental pollution has been seen to cause a catastrophic effect on the River Mahananda, Malda, West Bengal, due to the discharge of untreated urban wastes and wastewater into the riverine system resulting in the decline of several local fish species owing to deteriorating water quality. Hence, the objective of this work was to assess the alteration of different physicochemical parameters of water in the River Mahananda owing to pollution during various seasons, and to examine their toxicological effects on the intracellular antioxidant system and histological parameters in Cirrhinus reba. The WPIs of the polluted sampling sites declined significantly from fall to summer. The season-based principal component analysis indicated that TDS, dissolved oxygen, total hardness, total alkalinity, free chlorine, chloride, copper, and zinc were the most common descriptors for the physicochemical alterations of the River Mahananda, reflecting its prominent pollution portfolio. SOD, CAT, GPx, GR, and GSH were found significantly (p < 0.05, p < 0.01, and p < 0.001) decreased in liver of C. reba collected from polluted sites compared to the control. The acetylcholinesterase activity was noted to increase significantly (p < 0.05 and p < 0.01) in an order of S2 > S3 > S4 > S1. A several-fold increase in TBARS level was observed in C. reba collected from polluted sites during summer, compared to the control. Major histopathological changes were observed in summer and spring in liver, kidney and gill tissues of C. reba. In conclusion, while certain principal components were significant predictors for various biochemical parameters, the overall model showed varying degrees of predictive power, highlighting the need for further research with larger sample size and potentially more comprehensive modelling strategies.