STRESS RESPONSES AS BIOMARKERS OF SENSITIVITY IN LABEO ROHITA EXPOSED TO LIME TREATED SLUDGE FILTRATE FROM PAPER AND PULP INDUSTRY

摘要

In this study, Labeo rohita were exposed to filtrates from concentrated lime treated sludge, fly ash and sludge without lime treatment obtained from paper and pulp mill using static bioassay over a period of 96 h. Mortality (100%) was observed in concentrated lime treated sludge filtrate and 10% dilution within 24 h exposure indicating its toxic potential. Concentrated filtrate of lime treated sludge and its 10% dilution contained high concentrations of heavy metals like cadmium, chromium, copper, nickel etc which could have led to the mortality of the fish. Filtrates of fly ash (10% mortality) and without lime treatment (0% mortality) are non-toxic to fish. Vital physiological and biochemical responses like oxygen consumption and gill ventilation,ionic composition and total glycogen were examined in L. rohita exposed to 50% and 100% dilutions of lime treated sludge filtrate over a period of 96 h. Though no mortality was observed, significant depression (P<0.01) in the metabolic rate of fish withincreased ventilation frequency was seen from 48 h until 96 h in 50% dilution while it was insignificant in 100% dilution. A similar trend was also seen in the total glycogen content of the fish. Impaired osmoregulation due to disturbed ionic compositionwas observed in fish exposed to 50% dilution of the lime treated sludge filtrate while there is no such change in 100% dilution. These findings demonstrate that sludge from paper and pulp mills is toxic to fish and elicits subtle responses that can serve as early warnings of environmental deterioration.