Effect of Tannery Effluent on Oxygen Consumption and Accumulation of Toxic Metal in Freshwater Fish Danio rerio (Hamilton)

Raw tannery effluent is toxic which may be lethal or sublethal concentration in aquatic environment. The present study deals with the effect of tannery effluent on oxygen consumption and metal accumulation in freshwater fish Danio rerio. Oxygen consumption of an animal is the important physiological parameters to assess the toxic stress because it is a valuable indication of energy expenditure and metabolism. The present study showed that the rate of oxygen consumption decreased in 24-120 hours in sublethal concentration compared with control. The levels of Cr accumulated tissues (gill,muscle,liver) were analysed through the Atomic absorption Septrophotometer. The results show the Cr concentration were HCG > HCM > MCG > MCM > LCG > LCM > HCL > MCL > LCL. The results were plotted and discussed in details. Keyword: Danio rerio; tannery effluent; oxygen consumption; bioaccumulation P.Sivakumar et al 602 J Pharm Chem Biol Sci , December 2015-February 2016; 3(4: 601-607 Tannery effluents are ranked as the highest pollutants all among the industrial wastes. They are especially large contributors of chromium pollution. The tannery waste waters continue to cause negative effects on the aquatic organisms. Fishes are the simple and reliable biomarkers of pollution of aquatic bodies. When fish are exposed to elevated levels of metal in a polluted aquatic ecosystem, they tend to take these metals up from their direct environment [2]. The respiratory potential or oxygen consumption of an animal is the important physiological parameters to assess the toxic stress, because it is a valuable indicator of energy expenditure in particular and metabolism in general [3]. Oxygen consumption has been used as an indirect indicator of metabolism of fish [4] and the energetic cost of ionic and osmotic regulations seems to play a significant role in growth rates [5]. Therefore, it is important to know the oxygen consumption of Danio rerio exposed to 5%, 10%, 15%, 20% and 25% tannery effluent concentration. The present study is aimed to determine the acute toxicity of tannery effluent with reference to its effects on behaviour and the oxygen consumption to the freshwater fish Danio rerio. Accumulation of metals in the fish tissues were reported by many authors [6-8]. The present investigation was analyzed the Cr metal concentration level in the muscle, gill and liver tissues of freshwater fish Danio rerio. Atomic Absorption Spectrometry (AAS) is one of the most favored techniques for determination of toxic element in biological samples as well as living tissues. The aim of the present work is to determine the toxic element in Danio rerio using AAS method and to evaluate the level of toxicity. MATERIALS AND METHODS The test fish Danio rerio of length 4.7 ± 1.0 cm and 3.9 ± 1gm of body weight were collected from local aquafarm and acclimated to the laboratory conditions for 60 days. 200 individuals were used for the experiment. They were stored in large rectangular FRP tanks and water was aerated continuously to maintain optimum level of dissolved oxygen. The fish were fed with artificial fish pellet on every day and the water was renewed every day by routine cleaning of aquaria to remove unconsumed food, faecal matter or dead fish. The fish were acclimatized to the laboratory conditions at 28  2C. After acclimation, feeding was stopped two days before the commencement of the experiment in order to avoid faecal contamination. FRP tanks (20L capacity) filled with various concentration of raw tannery effluent mixed with dechlorinated tap water was used for the experiment. The tannery effluent for the present study was collected from a tannery at Ambur, Vellore District, Tamil Nadu. Only the raw effluent was used for the study. Fishes were divided into six groups of 10 fishes each. They were classified in to control, 5%, 10%, 15%, 20% and 25% sub-lethal concentration of tannery effluent. The control was maintained in normal tap water without the metal toxicant. The test was conducted for 120hrs and observations were made continuously during the period of experimentation. Each experiment was set up in triplicate and only the arithmetic mean of the three experiments at each concentration was taken to express the results. The dissolved oxygen content in the initial and final water samples were estimated by Wrinkler’s modified method [9]. The difference in the dissolved oxygen content between initial and final water samples represents the amount of oxygen consumed by the fish. P.Sivakumar et al 603 J Pharm Chem Biol Sci , December 2015-February 2016; 3(4: 601-607 AAS is a spectroanalytical procedure for the quantitative determination of chemical elements using the absorption of optical radiation (light) by free atoms in the gaseous state. In analytical chemistry the technique is used for determining the concentration of a particular element (the analyte) in a sample to be analyzed. The modern form of AAS was largely developed during the 1950s by a team of Australian chemists. They were led by Sir Alan Walsh at the Commonwealth Scientific and Industrial Research Organisation (CSIRO), Division of Chemical Physics, in Melbourne, Australia. 10ml of fish tissue sample (gill, muscle, liver) from different concentrations of raw tannery effluent were centrifuged at 2500rpm on 15min. The clear supernatant was used for AAS analysis. The values obtained by AAS analysis represent the residual concentration of tannery effluent in the solution (chromium).