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Vidyodaya 1. ofSci. (/999) Vol 8 203-206

Bioaccumulation of heavy metals in three species of freshwater fish from Weras Ganga: evidence for bio magnification

Mayuri R. Wijesinghe, Y. N. A. Jayatunga and R. Hewamanna1,2 Department of Zoology 3. Radio isotope Centre

University of ColomboReceived on 99.02.14Accepted on 99.08.19

Abstract:This paper reports the evidence for biomagnification in three species

of fresh water fish: Oreochromis mossambicus, Ophiocephalus striatus andHeteropneustesfossilis with different feeding habits, from Weras Ganga inthe Colombo District.

The muscle, gills, kidney, gonad and Iiver of fish were analyzed by theX-ray fluorescence method and the mean concentrations of heavy metals ineach species, were computed in ug/g dry organ weight.

It was seen that the piscivore (Ophiocephalus striatus) had muchhigher levels (aggregated means for all the organs) of Cu (131.67.1O), Zn(639.212.30), Cr (3.031.23), Ni (ll.062.35) and Ti (l8.62.30) thanboth the omnivore (Oreochromis mossambicus) and the detritivore(Heteropneustes fossilis}, showing evidence of biomagnification. Theconcentrations of Fe (l463.422.70) and Mn (l83.97.07) were highest inOreochromis mossambicus. Further studies of its feeding habit may providean explanation for this. The lowest concentration of all metals was recordedin the detritivore.Key words: Bioaccumulation, heavy metals, fresh water fish

1. IntroductionMany fresh' water bodies in the Colombo district are subject to heavymetal pollution through the discharge of industrial effluents, and fish from

these water bodies are being caught for human consumption. Three waterbodies from the Colombo district were selected for a study of various aspectsofbioaccumulation of heavy metals infresh water fish. This paper deals withthe study ofbioaccumulation of heavy metals in three species offish, withdifferent feeding habits, from Weras Ganga.

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20 4 Wijesillghe Jayatunga and Hewamanna

Biomagnifiaction, whereby pollutants show an increase in trophiclevel, has been used to explain the high concentration of some pollutants (e.g.DDT) in top carnivores such as raptors (Leblance, 1995). As fish occupy animportant position in aquatic food chains, and are being consumed byhumans it would be useful to gain an insight into the potential risks from theconsumption of fish occupying different trophic levels in a food chain. Thethree species of fish selected for the study were, Ophiocephalus striatus, apiscivore, Oreochromis mossambicus, an omnivore and Heteropneustesfossilis, a detrivore.

2. Materials and methodsThe fish used in this study were collected from the Weras Gangabetween 6 and 8 am during the period from March to April, 1995. All the

individuals of the three species were young adults. On collection, the fishwere immediately packed with ice in polythene bags, transported to thelaboratory, and stored at - 200C. The total number of fish subjected to theanalysis were Oreochromis mossambicus 56, Heteropneustesfossilis 15andOphiocephalus striatus 11. When taken for analysis the fishes were thawedand the individuals of each species were divided into three compositesamples. The gills, gonads, kidney, liver, and a section of the muscle weredissected out, washed thoroughly, oven dried to a constant weight at 105C,and their weights were recorded. The samples were then ashed at 400 C forsix hours in a muffle furnace and stored in a dessicator. The temperature waskept at 400 C as a higher temperature could cause the loss of volatileelements (IAEA, 1980 & APHA, 1980).

The metal analysis was done by the energy dispersive X-ray fluores-cence mul ti-element analyzing method (Bearse et al., 1974) using the modelSEA 201OLXRF Element Monitor version 3.1, at preset conditions of 3000seconds, 10Ilm aperture and 261lA current. The metal concentrations of eachcomposite sample were calculated as Ilg/g dry organ weight. The. data fromthree composite samples for each organ were used to calculate the meanconcentration for the different organs. The mean concentration for eachspecies was then computed from the means of the heavy metal concentra-tions in different organs.

Analysis of dataA one-way ANOV A was applied to the mean concentrations of the threespecies to determine whether the levels of the metals were significantlydifferent in the three species. In instances where a statistically significantresult was obtained with ANOV A the data were subject to HSD test todeterm ine w hether the d ifference in levels betw een any tw o species, w assignificant.

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Bioaccumlation of heavy metals ill fish 205

3. Results:The heavy metals in the three species of fish are given in Table 1. Itwas seen that Ophiocephalus striatus (piscivore) had significantly higherconcentration ( p

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Table 1: Mean concentration (ug/g dry WI.) metal's in Heteropneustes fossilis, Ophiocephalus striatusand Oreochoromis mossambicus of Weras Ganga.

Hete ropneustes fossilis Ophiocephalus striatus Oreochromis mossambicusCu 806.75 131.647. I 8.8852.09Zn 71.555.03 639.212.3 116.573.9Fe 229.287.74 1130.2321.89 1463.3822.7Mn 43.092.32 93. I93.66 I83.9O7.07Cd ND 18.811.84 O.225O.33Cr ND 3.031.23 NDNi O.42O.34 11.062.35 O.47O.48Ti 8.281.95 18.62.3 1.975O.993Values below detectable limit s are denoted by ND

6. References1. APHA (1980). Standard methods for the examination of water and

waste water. American Public Health Association, American waterworks association water pollution control federation, Washington D.C

2. Bearse, R. C, Close D. A. Malanify J. J. and Umbarger C J. (1974).Elemental analysis of whole blood using proton induced X-rayemmission. Annal. Chem. 46 p. 499.

3. Breg, H., Kiibus, M. and Kautsky, N. (1993). Heavy metals in the lakeKariba-A man-made tropical lake. lnst. for Systemerology, 448(8).

4. Dallinger, R., Prossi, F., Segner, H. and Back, H. (1987). Contami-nated food and uptake of heavy metals in fish, A review and proposalfor further research. Oecologia 73 p. 91-98.

5. IAEA (1980). Elemental anaysis of biological materials, currentpoblems and techniques with special reference to trace elements.Techical series, 197 Austria.

6. Leblanc, G. A. (1995). Trophic level differences in the bioaccumulationof chemicals: Implications in assessing environmentalbiomagnification. Environ Sc. and Tech. 29 (1): 154-160.

7. Martin, M. H. and Coughtrey, P. J. (1982). Biological monitoring ofheavy metal pollution: Land and air (pollution monitoring series)Elsevier Applied science, London. p. 22-295.