Abstract

Aquatic ecosystems are exposed to anthropogenic stressors and pollutants, including chemical pollutants, temperature, salinity, and habitat degradation, that threaten their biodiversity. Current conservation initiatives base their environmental assessment solely on the chemistry of water and sediments, neglecting the more telling indicators of ecological stress: organisms' physiological responses. This research investigates a set of biomarkers consisting of the oxidative-stress enzymes (catalase, superoxide dismutase, glutathione peroxidase), the neurotoxicity marker (acetylcholinesterase), and condition indices (hepatosomatic index, condition factor) on the freshwater carp Labeo rohita sampled from different reaches of the Hooghly River, India, under different environmental-stress situations. Findings indicate that condition and histological parameters respond to pollutant impacts over extended periods, whereas the oxidative-stress and neurotoxicity biomarkers react more rapidly. Supporting their diagnostic and predictive capabilities, correlation and multivariate analyses associated the biomarkers with critical physicochemical variables. The integrated biomarker response (IBR) index, with high precision, identifies a stress gradient, providing a quantitative method to support conservation. This biomarker system identifies stress to target specific sites and times for management action within aquatic conservation initiatives.

Keywords: Biomarkers, Oxidative stress, Fish conservation, Aquatic pollution, Early-warning, Environmental monitoring