Amr A. Abdel-Khalek

Risk Assessment and Toxic Effects of Metal Pollution in Two Cultured and Wild Fish Species from Highly Degraded Aquatic Habitats

Lake Qaroun is an inland lake at the lowest part of El-Fayoum depression, Egypt. It receives agricultural and domestic non-treated drainage waters, which are also used for aquaculture in Qaroun area. The results of the present study aimed to provide comparable data between wild (collected from Lake Qaroun) and cultured (collected from Qaroun fish farms and the reference site) Nile tilapia Oreochromis niloticus and mullet Mugil cephalus, as indicators of natural and anthropogenic impacts on aquatic ecosystem as well as to evaluate the human hazard index associated with fish consumption. Metal concentrations in fish tissues showed a species-specific bioaccumulation pattern. Statistically significant differences were observed in the mean metal concentrations with lower bioavailability in M. cephalus compared with O. niloticus in internal vital organs (liver, kidney, and muscle) but much higher in external organs (gill and skin). Histopathological alterations and evident damages were observed in gill, liver, and kidney of both species collected from Lake Qaroun and Qaroun fish farms compared with those from the reference site. The results showed significant increase of plasma aspartate aminotransferase and alanine aminotransferase activity as well as creatinine and uric acid concentration in both fish species from polluted locations. The human health hazard index showed that the cumulative risk greatly increases with increasing fish consumption rate, thus yielding an alarming concern for consumer health.

Genotoxic effects of metal pollution in two fish species, Oreochromis niloticus and Mugil cephalus, from highly degraded aquatic habitats

In Egypt, Lake Qaroun and its neighbouring fish farms are in a serious environmental situation as a result of pollution by agricultural sewage and domestic non-treated discharges. The present study aims to evaluate genotoxic effects of toxic metals in cultured and wild Nile tilapia, Oreochromis niloticus and mullet, Mugil cephalus collected from these contaminated aquatic habitats, in comparison with fish from a non-polluted reference site. Heavy-metal concentrations (Cu(2+), Zn(2+), Pb(2+), Fe(2+) and Mn(2+)) in water and sediment samples were recorded. The condition factor (CF) was taken as a general biomarker of the health of the fish, and genotoxicity assays such as the micronucleus (MN) test and a DNA-fragmentation assay were carried out on the fish species studied. In addition to micronuclei, other nuclear abnormalities (NA) were assessed in fish erythrocytes. Degradation of the studied aquatic habitats revealed species-specific effects. A significant decrease in CF values associated with a significant elevation in MN and NA frequencies was observed in fish collected from the polluted areas compared with those from the reference site. Moreover, mixed smearing and laddering of DNA fragments in gills and liver samples of both fish species collected from the polluted areas indicate an intricate pollution condition. Results of the present study show the significance of integrating a set of biomarkers to identify the effects of anthropogenic pollution. High concentrations of heavy metals have a potential genotoxic effects, and genotoxicity is possibly related to agricultural and domestic activities.

The Chronic Exposure to Discharges of Sabal Drain Induces Oxidative Stress and Histopathological Alterations in Oreochromis niloticus

To study whether the effluents of Sabal drain could affect the health status of Oreochromis niloticus; site2 (south part of main canal), site3 (at the canal outlet), site4 (north part of main canal) and site1 (reference site) were selected. Compared to the reference fish, activities of superoxide dismutase and glutathione peroxidase in addition to glutathione reduced and thiobarbituric acid reactive substances concentrations of the gills showed significant (p < 0.05) increase with different levels in all studied sites. Whereas, catalase activities revealed significant (p < 0.05) decrease in all studied sites with maximum decrease in site3. The recorded histopathological lesions were correlated with the distance from discharge point. Gills, liver and kidney of site3 had the worst histopathological conditions based on the frequency of alterations appearance and size of the affected areas. While, the regressive alterations that recorded in site2 and site4 suggest the onset of adaptive histological mechanisms.

Assessment of Ecosystem Condition Using Some Biotic and Abiotic Components along Ashtoum El-Gamil Protected Area, Lake Manzala, Egypt = تقييم حالة النظام البيئي باستخدام بعض المكونات الحيوية واللاحيوية بمحمية أشتوم الجميل، بحيرة المنزلة، مصر

The present field investigation considers monitoring some biotic (four fish species and plankton) and abiotic (water and sediment) components as indicators of natural and anthropogenic impacts on aquatic ecosystem during winter and summer seasons. This included measurement of metal concentrations in water, sediment and plankton samples, conducting a risk assessment of sediment pollution and evaluating fish body condition indices as well as oxidative stress biomarkers. The detected seasonal variation among these parameters showed site-related and species-specific patterns. The levels of metal in plankton samples were, in most cases, higher than those in sediment samples and the lowest levels were detected in water samples. Heavy metal enrichment status in sediment showed mostly a progressive pollution condition during summer as well as seasonal fluctuation in levels of Zn and Pb along the studied sites. The scaled mass index (SMI), as a fish body mass-length index, performed better in indicating the fish body condition in relation to the ecosystem condition, where it showed significant increase in case of the flathead mullet (Mugil cephalus) and the green tilapia (Tilapia zillii) during summer and significant increase in the Nile tilapia (Oreochromis niloticus) and the catfish (Clarias gariepinus) during winter. Mullet showed the highest levels of oxidative stress biomarkers (superoxide dismutase, catalase and malondialdehyde), while Nile tilapia showed the lowest levels. The present study affirms the significance of monitoring sediment geoaccumulation index (Igeo) and pollution load index (PLI) as well as SMI and oxidative stress biomarkers as sensitive indicators of intricate pollution conditions and their effects on aquatic ecosystems.