Pages 121–127
Abstract
Research summary supplied by the authors
The present study which was conducted in East Kolkata Wetlands investigates the impact of tannery effluents on aquatic biota, focusing on fish (Labeo rohita, Catla catla, Cirrhinus mrigala, Oreochromis niloticus, Oreochromis mossambicus) as bioindicators for sustainable environmental management. Physicochemical analyses revealed distinct variations between wastewater-fed and uncontaminated fishponds, with parameters such as temperature, pH, dissolved oxygen, alkalinity and trace metal concentrations significantly influenced by effluent exposure. Wastewater-fed ponds exhibited elevated levels of toxic metals, notably exceeding recommended surface water limits, resulting in metal bioaccumulation primarily in fish liver and gills, while muscle and brain tissues showed lower concentrations. Fish demonstrated physiological adaptations, including increased metallothionein expression, which chelates heavy metals, mitigating toxicity and maintaining metal homeostasis. Despite metal stress and reduced total protein levels in tissues, fish yield remained high, indicating effective acclimatization mechanisms. Enzymatic biomarkers such as alkaline phosphatase, acid phosphatase, alanine aminotransferase and aspartate aminotransferase showed elevated activities, reflecting enhanced liver detoxification and stress responses. Additionally, oxidative stress markers, including superoxide dismutase and cytochrome P450, were significantly induced, suggesting reactive oxygen species generation due to metal overload. Immunotoxicological assessments revealed suppression of nonspecific cytotoxic cells, indicating compromised innate immunity linked to metal exposure. These findings highlight the dual role of fish as both indicators of environmental contamination and resilient organisms capable of physiological adjustments under heavy metal stress. The study underscores the importance of monitoring bioaccumulation patterns and biochemical responses in fish to evaluate aquatic ecosystem health and inform sustainable management strategies for wastewater-impacted environments. Keywords Bioindicator, Tannery Effluent, Heavy Metals, Metallothionein, Oxidative Stress