Abstract
East Calcutta Wetland ecosystem is a Ramsar Site in India covering almost 51 km2 and is one of the largest of its type. This
wetland receives a massive load of almost untreated industrial and domestic effluents every day, throughout the year, that has
been effectively utilized in pisciculture for having a better yield (2.85 metric tons of fish per 0.01 km2 of water body per annum).
The present investigation was carried out to study the toxicity of the untreated effluents discharged from tanneries located at the
fringe of East Calcutta wetlands. Guppy (Poecilia reticulata) was chosen as a model fish and was exposed to three different
sublethal concentrations (3%, 6% and 9%) of composite tannery effluents (TE) for different time periods (4 days, 7 days and 15
days). Exposed fish livers were analyzed for metallothionein (MT, a ubiquitous metal binding protein), cytochrome
P4501A1+1A2 (CYP, a major family of xenobiotic metabolizing enzyme in fish biosystem) and nonspecific cytotoxic cells
(NCCs, a major group of innate immune system in fish) expressions applying indirect enzyme-linked immunosorbent assay
(ELISA) procedure. Results showed that expression of all the three chosen biomarkers were significantly dose and time
dependent upon tannery effluent exposure. Major significances drawn from the present study was that fish species cultivated in
east Calcutta wetland ecosystem are under potential threat of contamination and stress induced by composite tannery effluents
that could lead to adverse physiological conditions. Moreover, these findings could be important in terms of designing
biomarkers for early environmental warning system and also for monitoring fish health.