Concentrations of Heavy Metals in Sediment and Selected Organisms in Lukut River, Malaysia, and Their Toxicological Effects on Penaeus Monodon (Fabricius) Juveniles
Safahieh, Alireza (2007) Concentrations of Heavy Metals in Sediment and Selected Organisms in Lukut River, Malaysia, and Their Toxicological Effects on Penaeus Monodon (Fabricius) Juveniles. PhD thesis, Universiti Putra Malaysia.
The status of heavy metals contamination in Lukut River, Negeri Sembilan, Malaysia was studied in September 2003. In general, except for Pb in the water, the level of heavy metals in the water and sediment of Lukut River were found to be within the range of other Malaysian Rivers. The metals concentrations in T. telescopium and the prawns P. monodon and P. merguiensis was within the range of heavy metal measured in other gastropods or prawn species previously studied in Malaysia indicating no serious metal pollution exists in the study area. Heavy metal concentration in the muscle tissues of the prawns was found to be lower than maximum permissible levels recommended for human consumption. High level of Pb was found in the water of Lukut River (390.10 μg/l) which was found to be relatively higher than some Malaysian rivers. The pattern of Pb concentration in water samples and low Pb level in the sediment suggested that dissolved Pb was originated from the sea–based inputs. The sublethal toxicity of the metals on growth, moulting and Ca content in exoskeleton of P. monodon juveniles were also investigated in 21 days period. Results indicated that after 21 days the juveniles exposed to Cu concentration of 1000 μg/l, Zn concentration of 1000 μg/l, Cd concentration of 160 μg/l and Pb concentration of 316 μg/l or above grew slower than controls (P<0.05). Among the metals studied, Cu and Zn were found to have an inhibition effect on exoskeleton calcification. The lowest concentration caused reduction in exoskeleton calcification was 100 μg/l and 1000 μg/l for Cu and Zn respectively. Metals exposure was also affected the moulting of P. monodon. The period of molt cycle was increased significantly in the prawns exposed to 3160 μg/l Cu, 1000 μg/l Zn, 160 μg/l Cd and 316 μg/l Pb. However, low Cu and Zn concentrations were found in Lukut River do not affect the calcification of the prawn’s exoskeleton or their molting. Penaeus monodon does not regulate the level of metals in the body. It was found to accumulate heavy metals (Cu, Zn, Cd and Pb) in proportion of external metal concentrations. Meanwhile the metals accumulation in muscle, exoskeleton and remainder were found to perform in different rates. The highest accumulation rate for Zn and Cd was found in exoskeleton while the highest accumulation rate of Cu and Pb was found in remainder. In addition, the lowest accumulation rates for all of the studied metals were found in the muscle tissue. Among the metals studied Cu and Pb were accumulated faster than Cd and Zn. Heavy metals depuration from muscle, exoskeleton and remainder of tissues were studied during one week duration. The fastest depuration of Zn, Cd and Pb was found in exoskeleton, while Cu was mainly depurated from the remainder of tissues. Furthermore among the metals studied Cu and Pb depurated faster than Zn and Cd. Moulting was found to cause no significant reduction in the Cu, Zn and Cd concentration in the moulted prawns. On the other hand it caused significant reduction of Pb content in the prawn’s body. Comparison between exoskeleton of the exposed intermolts and the exuviae of the newly moulted prawns (post moults) indicated that Pb concentration in the moults was significantly higher than exoskeleton which indicates that molting could be a effective way to eliminate the accumulated Pb from the body. In general, based on the results from field study (analysis of water, sediment and biological samples) it is concluded that Lukut River is not polluted by heavy metals. Except for Pb, the level of metals in the water of Lukut River is not high enough to cause any impact either on aquacultured or on wild prawns.
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