Metallothionein as a Biomarker to Assess the Effects of Pollution on Indian Major Carp Species from Wastewater-Fed Fishponds of East Calcutta Wetlands (a Ramsar Site)

Abstract

Metals are one of the major chemical toxicants that can perturb environmental homogeneity by their prolonged persistence and complex interactions. Bioaccumulation of any metal above its threshold level invariably results in stress often leading to irreversible physiological conditions. The present investigation was carried out to study the potential stress that fish species are facing in wastewater-fed (contaminated) fishponds in East Calcutta Wetlands (ECWs), manifested in total protein and metallothionein (MT) concentrations. Indian major carps (IMCs) – rohu (Labeo rohita), katla (Catla catla) and mrigel (Cirrhinus mrigala) were used as suitable fish models. Total protein concentration of different fish tissues were found to be always lower in wastewater-fed fishponds when compared to fish tissues from freshwater-fed (uncontaminated) fishponds, while an indirect enzyme-linked immunosorbent assay (ELISA) revealed a higher expression of MT in all the fish tissues collected from wastewater-fed fishponds. Major significances drawn from the present study were that fish species cultivated in east Calcutta wetland, with its ecosystem being under a potential threat of contamination and stress induced by composite effluents, could lead to adverse physiological conditions. Moreover, these findings could be important in terms of designing biomarkers for an early environmental warning system and also for monitoring fish health.