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.
Highlights
Urbanization and industrialization have persistently contaminated most of the natural environment, and major cities around the globe are under a budding threat of pollution
In fish species protein acts as the major macronutrient that controls energy gain or loss (Diana 1982) and an increase in pollutants, including heavy metals, often results in decreased total protein concentration in fish tissues (Goel et al 1988; Almeida et al 2001)
Total protein concentration of different fish tissues collected from both contaminated and uncontaminated fishponds have been presented in Figs 2 – 5
Summary
Urbanization and industrialization have persistently contaminated most of the natural environment, and major cities around the globe are under a budding threat of pollution. In the eastern fringe of city Calcutta (recently renamed as Kolkata) there lies East Calcutta Wetland, a Ramsar site (No 1208) in West Bengal, India (lat 22°33′ - 22°40′N, long 88°25′ - 88°35′ E), the biggest urban wetland ecosystem covering around 12,771 ha area. This wetland receives untreated industrial run-off from almost 6000 large- and small-scale industrial establishments (including tanneries) along with Calcutta metropolitan’s (12 million inhabitants) domestic sewage throughout the year.
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