الفهرس 
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Abstract
Water pollution is a matter of great concern throughout the world due to existing of a wide range of pollutants. These pollutants can threat the water resources and cause the damage to aquatic organisms. Industrial, agricultural development and various human activities led to the water pollution and exposed the aquatic organisms to different classes of pollutants. Prolonged exposure to water pollutants even in very low concentrations may induce morphological, histological and biochemical alterations. As well it is also possible that environmental toxicants may increase the susceptibility of aquatic animals to various diseases by interfering with the normal functioning of their immune, reproductive and developmental processes. Some of these pollutants may find their way into the human system through the food chain and may accumulate in his tissues causing toxicity.
This study was conducted on a sample of 200 apparently healthy Oreochromis niloticus, with average body weight of 47.0 ± 8.6 g and 14.9 ± 0.2 cm in length collected from Edku Lake. This lake is exposed to various types of wastes including industrial, agricultural and domestic sewage via four main drains discharge into the lake. Edku, El-khairy, El-Boseily, and Barzik drains. Besides, domestic sewage and industrial wastes, discharged into the sea from the industrial complex along the Abu Qir coast via El Tabia pumping station, west of El-Maadyah. They may at times enter the lagoon through the inlet at El-Maadyah which connects the lake with the sea. Fish samples collected at two sites of Edku Lake, first site was El-Maadyah region and the second site was the Edku drain and were compared with the recovery group (of El-Maadyah region supplied with chlorine free tap water and was left for a month).
The physico-chemical characteristics of water were studied and smears of blood were examined to detect the nuclear and cytoplasmic alterations.
Biochemical and immunological analysis of serum were performed. In addition to measuring some biochemical analysis of tissues such as liver and muscle as hepatic antioxidant enzymes (SOD, CAT, GPx and GSH). Besides body chemical composition analysis as total proteins, lipids, water content, ash of the dorsal white muscles and the energy value. Moreover immunochemical analysis of hepatic Metallothioneins using Elisa was performed. As well, histopathological examination of fish liver and muscle tissues.
The study of the physico-chemical properties of water revealed that there was a significant decrease of dissolved oxygen in Edku drain region in compared to the other both groups. Besides a significant increase in salinity value in El-Maadyaah region compared to the other both groups.
The biochemical analysis
The present study revealed a decrease in serum total protein, albumin, and total lipids, liver function enzymes (ALT and AST) was observed in El-Maadyah and Edku drain groups compared to recovery group. Besides, a significance decrease in kidney function (creatinine level), muscle total protein level, energy value and muscle ash content was found in Edku drain group compared to the other both sites.
While the results revealed that there was an increase in the levels of serum glucose and antioxidant enzymes (SOD, CAT, GPx and GSH) in El-Maadyah and Edku drain groups compared to the recovery group. Besides, an increase in the muscle water content and a significant increase in muscle total lipids were found in Edku drain group compared to the other both sites.
The immunological analysis
The results revealed that there was a decrease in the bactericidal activity in El-Maadyah and Edku drain groups compared to recovery group. While there was an increase in the lysozyme and hepatic metallothionein MT in both polluted sites compared to the recovery group.
The nuclear abnormalities of fish erythrocytes:
The present study revealed genotoxicity abnormalities in the nucleus of fish erythrocytes when examined under microscope include:
Micronuclei, Binuclei, Blebbed nuclei, Kidney-shaped nuclei, Lobed nuclei, Bilobed nuclei, Notched nuclei, Vacuolated nuclei, Hook-shaped nuclei, Fragmented apoptotic nuclei, enucleus.
The frequencies of these abnormalities were elevated in both polluted sited compared to the recovery group
The changes of cytoplasm of fish erythrocytes (cytotoxicity) include:
Swelled cells, vacuolated cytoplasm, microcytes, acanthocytes, echinocytes, tear-DROP like, sickle cell, nuclear retraction, Fused cells and hemolyzed cells.
The present study revealed that the frequencies of these abnormalities were elevated in both polluted sited compared to recovery group
Histopathological alterations in liver and hepatopancreas
The present study revealed histopathological alterations in the liver and hepatopancreas of both polluted sites compared to the recovery group.
The most prominent lesions were parasitic granuloma (was observed in El-Maadyah group), necrosis of hepatocytes, hydropic, vacuolar and fatty degeneration of hepatocytes. In addition to degenerated pancreatocytes (was noticed in El-Maadyah group) and hypertrophy of pancreatic tissue (was noticed in Edku drain group). Also revealed dilation and congestion of blood vessels, hemolysis, hemorrhage and thrombosis. chronic inflammatory reaction due to parasitic infestation (aggregation of melanomacrophages and eosinophilic granular cells) and increase proliferation of the intralobular and interlobular connective tissue were detected.
Histopathological alterations in muscle tissue
The present study revealed histopathological alterations in the muscle tissue of both polluted sites compared to the recover group. The most prominent lesions were:
Hyalinized and necrotic muscle fibers, vacuolar degeneration, dispersed muscle bundles by edema (Edku drain more than El-Maadyah group). In addition to parasitic granuloma (was noticed in El-Maadyah group), infiltration of lymphocytes and aggregation of melanomacrophages. As well, fatty tissue, glycogen granules and variable amount of connective tissue proliferation between muscle bundles (El-Maadyah more than Edku drain).
The present study revealed that the levels of pathological alterations in both liver and muscles were elevated in both polluted sites compared to the recovery group.