HEAVY METALS in FISH AS a BIOINDICATOR for MONITORING of METAL RECALCITRANTS in MALAYSIAN RIVERS Maimon Abdullah1, Salem Alzahra

ID: 326 HEAVY METALS IN FISH AS A BIOINDICATOR FOR MONITORING OF METAL RECALCITRANTS IN MALAYSIAN RIVERS Maimon Abdullah1, Salem Alzahrani2 and Abdullah Samat3 1,2,3 School of Environmental and Natural Resource Sciences, Faculty of Science and Technology, National University of Malaysia (UKM), Bangi 43600 Selangor, Malaysia The Langat River is one of the main sources of water supply for the Selangor state in Malaysia and heavy metals are among the most persistent types of pollutants that can pose a threat to the aquatic ecosystem and human health. This study was conducted to determine the concentrations of heavy metals, namely aluminum (Al), cadmium (Cd), copper (Cu), chromium (Cr), iron (Fe), manganese (Mn), nickel (Ni), lead (Pb) and zinc (Zn) in the bones, gills, guts, fins, head, muscles and skin of Tilapia, which is a widespread species of freshwater fish that can be used as a potentially useful bioindicator for monitoring metal pollution in water resources. A total of 33 fishes were collected from three stations located in selected parts of the Langat River during two sampling occasions, in January and February 2009, respectively. The metal contents in dried fish samples were extracted by the acid digestion method and analyzed by inductively coupled plasma mass spectrometry (ICP-MS). Among the metals analyzed, Fe and Al were the most abundant in the different body parts, while Cd and Ni were the least abundant and were not detectable in the edible body parts. The mean concentrations of metals in Tilapia in descending order are as follows: Fe (4583±1.9); Al (2882±2.07); Zn (62.09±5.15); Mn (100.9±0.017); Cu (20.17±0.011); Pb (10.28±0.039); Cr (2.74±0.04); Ni (1.39±0.13) and Cd (20.17±0.011). Macro and trace element accumulation in fish can pose a health risk to consumers in a contaminated water catchment. However, the results of this study show that the metal contents in Tilapia sampled from the Langat River are still within the normal range except for Fe and Mn, which have exceeded the allowable limit set by the Malaysian Food Act (1983) and Food Regulations (1985). The Langat River is within the safety limit for potable water usage and the Tilapia fish harvested from the river is considered safe for human consumption. Keywords: heavy metals; Tilapia; biological indicator; Langat River Introduction As Malaysia undertakes to realize its vision 2020 through its industrialization and urban expansion policies (Muyibi et al. 2008), heavy metals pollution of rivers have become a matter of grave concern as reflected in several studies conducted locally, such as for Kelang River (Law and Singh 1986), Selangor River (Mat and Maah 1994), Linggi River (Khan and Lim 1994), Sepang River (Ismail and Ramli 1997) and Langat River (Sukiman 1989). The Klang-Langat River basin is undergoing a very intensive urbanization process due to rapid population growth and socioeconomic development, while the Langat River is one of the main sources of water supply for the Selangor state. Thus, the river status and its water quality should be continually monitored, particularly with respect to the heavy metals, which are among the most persistent types of pollutants that can pose a threat to the aquatic ecosystem and human health. The impacts of human activities on water bodies require appropriate monitoring tools to facilitate detection and characterization of the causes and sources of chemical, physical and biological impairment of the aquatic habitats. Among these tools, aquatic biota (fish, frogs, insects, benthos and plants) are identified as potential bioindicators to detect pollutant loads in water (Gibson et al. 1996). In tracking long-term changes ID: 326 of a specific water body such as a river system, fish (such as Tilapia, Oreochromis mossambicus) are known to be useful and reliable indicators of long-term effects and broad habitat conditions as highlighted by many investigators over the years (Brinley 1942, Araújo et al. 2000; Vidal, 2008). Tilapia is the common name for around 70 species of perch-like fishes (family Cichlidae) native to the fresh waters of tropical Africa (Bhassu et al. 2004). This study has been carried out to determine the metal concentrations in Tilapia and to screen for its potential as a bioindicator of water pollution by recalcitrants such as heavy metals in the Langat River and other water bodies in Malaysia. Material and Methods Study Area The Langat River Basin (area 2938 km2) lies in the mid western part of Peninsular Malaysia and flows through parts of the industrial area of the Klang Valley in two states, namely Selangor and Negeri Sembilan. The Langat River is about 120 km long and the main tributaries are the Semenyih River and the Labu River (Sukiman 1989). Fish samplings were conducted at three stations in selected parts of the Langat River tributary system. First station is located at Engineering Lake (EL) within the main campus of Universiti Kebangsaan Malaysia in Bangi. The second station is situated in the Langat River (LR) near Bandar Baru Bangi area and the third station is located at Cempaka Lake (CL), also in Bandar Baru Bangi (Figure 1). ID: 326 Figure 1 Three sampling stations in Langat River tributary system, Selangor Sample Collection A total of 33 fish samples were collected by using a cast net and scoop net with a mesh size of about 2.5 cm. Fresh fish samples were stored in cool boxes, each labeled with dates and location. Likewise, GPS and land use data were recorded for each sampling station. Morphological data of fish recorded are the total length (tip of caudal fin to head), standard length (front of caudal fin to head), and body weight, physical appearance and color. Fresh specimens were immediately taken to the ID: 326 laboratory and all samples were kept frozen in the refrigerator at -20 °C for further preparation and analysis works. Preparation of the Fish Samples Fish samples were each was separated into seven parts: head, muscles, gills, skin, gut, fin and long bone, using a stainless steel knife to prevent metal contamination. The fresh tissues were weighed, then oven-dried at 80 °C to constant weight. The dried samples were pounded into powder form using a mortar and pestle. Acid Digestion Method for Fish Heavy metals in fish body parts were extracted by the acid digestion method, using the Kjeldatherm digester model Gerhardt and following the AOAC standard method (1996). Powdered dried sample of fish part (0.5 g) was soaked in 2 ml of concentrated nitric acid in a PTFE beaker, and then fully digested in the Kjeldatherm digester at 100 °C (for about 2 hours); until the dark fumes turned white to indicate that all the nitric acid had evaporated. The digested samples were air-cooled, and then 2 ml of hydrochloric acid added, and further heated for one hour to complete the digestion, resulting in a clear yellowish solution. The cooled solution was filtered through an acid-resistant filter paper (0.90 µm pore size). The filtrate was further diluted with 25ml of distilled water and then analyzed for metals content using the inductively coupled plasma mass spectrometry (ICP-MS, model Perkin-Elmer OPTIMA 4300). Results and Discussion Sampling efforts using the cast nets were hampered by the presence of floating garbage and debris that were discarded in the upper and midstream parts of the Langat River. The body length of fish samples ranged from 11-22 cm, and the body weight ranged from 40-167 gm. Heavy Metals in Tilapia Aluminium (Al) Results showed that overall mean Al level for all the fish body parts (dry weight) was 250±97.54 µg/g (Table 1), with highest mean value from station 3 CL (428±241 µg/g) and the lowest, from station 2 LR (43.71±6.28 µg/g). Among the body parts, the highest mean Al concentration was in the guts (947.86±1174.34 µg/g), and the lowest, in the muscles (3.06±2.926 µg/g). Kruskal-Wallis H test shows that there are statistically significant differences in the Al contents of the various body parts, with the guts having the highest value of Al (Chi-Square=32.66, df;6, P<0.001). The effects of Al on fish behavior have not been reported much. In reviews of dietary studies in fish, Poston (1991) reported no adverse effects on growth, survival, or feed conversion in the Atlantic salmon fed up to 2000 μg/g dietary aluminum. Poston (1991) also noted that in fact, trace amounts of Al had some nutritional benefits to the Atlantic salmon, thus suggesting that Al may be an essential inorganic element and most likely metabolically regulated. However, other studies showed that under acid rain conditions (i.e., low pH), certain Al complexes can be toxic to fish even at low levels (Haines 1981). ID: 326 Table 1 Mean Al levels in the fish body parts sampled from the Langat River Al S1 S2 S3 Total Mean Skin 2.07±1.92 9.85±2.15 5.966±2.037 5.966±2.037 Bone 15.51±3.27 20.29±5.61 16.43±3.27 17.41±4.05 Fins 8.13±5.34 3.30±1.004 10.61±3.84 7.35±3.42 Muscles - 9.18±8.78 - 3.06±2.926 Gills 31.47±1.78 75.33±6.30 249.51±30.86 118.77±1298 Head 7.45±4.13 7.51±4.29 19.58±3.86 11.52±4.10 Gut 1882±296 2882±1664 - 1588±653.5 Total 277±44.36 428±241 43.71±6.28 250±97.54 Mean Nickel (Ni) Results showed that Ni concentrations for all the fish body parts ranged from 0.13±0.11 µg/g to 1.39 ±0.08 µg/g.

Load more