ABSTRACT
Heavy metal toxicity in aquatic life as a result of human activities poses a grave health threat to water quality, aquatic and human life. Parasites may serve as indicators of heavy metal pollution. This research investigated the health status of the fish Heterotis niloticus viz-a-viz quality of the water and sediments in Lekki lagoon, parasitic infection, presence of heavy metals and oxidative stress response in the liver and intestine of the fish. Parasites recovered were also analyzed for the extent of bioaccumulation of heavy metals. The metals in water, sediments, parasites, and fish were analyzed using Atomic Absorption Spectrometry. Heavy metal concentrations in the surface water were generally below regulatory limits of World Health Organization. Sediment had high levels of aluminium (124.78 mg/kg) and iron (327.41 mg/kg); other heavy metals were below regulatory limits. Tenuisentis niloticus, an acanthocephalan, was the only parasite recovered. Seventy (70) out of 100 fish sampled were infected with the parasite. T. niloticus bioaccumulated Cd, Ni, and Pb between 65 to 100 times more than the liver and 12 to 200 times more than the intestine. Other metals bioaccumulated from the host tissues by the parasite had the magnitude between 1 to 12 times as the liver and 1 to 30 times as the intestine. There were significant differences in the activities of antioxidant enzymes between the parasitized and non-parasitized fishes. Fish tissues also showed histological alterations, ranging from mild infiltration of inflammatory cells to moderate inflammation and haemorrhagic lesions. Human activities that introduce stressors into the lagoon should be controlled.
ABSTRACT
Toxicity studies in the aquatic ecosystem have shown that petrol and its product have adverse effects on aquatic biota. They are able to easily absorb these toxic substances into their bodies from sediment, water or even food items that are contaminated, thus impacting the food chain. In this study, water, sediment and fish (Heterotis niloticus) from the Epe Lagoon were investigated for the presence of BTEX (benzene, toluene, ethylbenzene and the three xylene isomers m, o and p-xylenes), and PAHs using GC-MS. Total concentration of BTEX in sediment and water was respectively 32.37 ± 1.07 µg/g, 49.86 ± 7.30 µg/L; while total concentration of BTEX in fish liver and intestine was 33.75 ± 10.09 and 40.16 ± 9.64 µg/g respectively. Benzene, 1,2-Dichlorobenzene and 1,3-Dichlorobenzene components of BTEX were not detected in both sediment and water. Total concentration of PAH in sediment and water was 7.46 ± 1.73 µg/g and 19.33 ± 1.31 µg/L respectively. Total PAHs concentration in liver and fish intestine was 141.23 ± 5.89 and 173.34 ± 4.677 µg/g respectively. Majority of the PAHs congeners were found to be higher than the acceptable limits. Findings from this study shows the need for continuous monitoring of our natural waters as the present situation portends a potential concern for ecological risk.