Lake Manzala Research Articles

Effect of Loading Rates in Free Water Surface Constructed Wetlands for Treating Polluted Water, Case Study :Bahr El-Baqar Drain (Dept.C)

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List of phytoplankton species of the northeastern part of Lake Manzala, Egypt

List of phytoplankton species of the northeastern part of Lake Manzala, Egypt

Monitoring of Some Heavy Metals in the Water and Three Submerged Plants of the Southern Part of Lake Manzala

Due to their potential to absorb and accumulate toxic heavy metals, three species of submerged aquatic plants, namely Potamogeton pectinatus L., Ceratophyllum demerssum L, and Myriophyllum spicatum L., were collected from ten different locations at the southern part of Lake Manzala and checked for the presence of heavy metals contents (Zn, Fe, Cu, Ni, Pb, and Cd); the values of contents, should they exist, were expressed as mg/g dry weight of the analyzed plant. The studied metals were also detected in water samples. Potamogeton pectinatus and Myriophyllum spicatum are the most active in absorbing of Pb, Cd, Zn, Ni, and Cu, respectively. Ceratophyllum demerssum immensely absorbed Fe and Pb. The presented study reveals that the submerged plants critically absorb and displace heavy metals from marine environments and they probably reduced the effect of high concentrations of these metals on the lake ecosystem. The submerged plants could be used as bioindicators; bioaccumulating agents for heavy metals in polluted water. It can be used in the sustainable management of water streams.

Evidence of two XX/XY sex-determining loci in the Stirling stock of Nile tilapia (Oreochromis niloticus)

Nile tilapia (Oreochromis niloticus) has been the subject of much research on sex determination due to the problems caused by maturation and reproduction in culture before harvest, and because of the emerging complexity of sex determination in this species. Analysis of the stock held at the University of Stirling, derived directly from Lake Manzala in Egypt about 41 years ago, detected an XX/XY locus in linkage group (LG) 1, and then a locus in LG20 that affected sex-ratio in some families, and was associated with the effects of elevated temperature on sex-ratio. Another XX/XY locus in LG23 with the candidate male-specific Amh gene was found recently to control sex determination in a Nile tilapia stock held at the Agricultural Research Organization (ARO) in Israel which was derived from a stock held at the University of Swansea, which was in turn derived from the Stirling stock. Extensive screening of the Stirling Nile tilapia stock for a marker in this male-specific Amh variant (Y-linked deletion in Amh exon VII) showed that this was present at a low frequency (7 out of 51 male broodstock, 13.73%) and associated with male phenotypic sex. It seems most likely that the dominance of the LG23 locus in sex determination in the ARO stock came about through founder effects associated with serial transfer. The presence of the previously undetected LG23 sex-determining locus may have led to some confusion in earlier attempts to develop YY males in the Stirling stock. Increased knowledge of sex determination in this species should aid marker-assisted selection (MAS) to produce all male fish to prevent unwanted reproduction in tilapia aquaculture, although the presence of multiple sex-determining loci in single stocks is likely to complicate such efforts.

Evaluation of Optimum Cropping Systems and Identify Soil Limiting Factors for Improvement of Agriculture Management by Spatial Modeling تقییم النظم المثلى لزراعة المحاصیل وتحدید العوامل المحددة بالتربة لتحسین الإدارة الزراعیة من خلال النمذجة المکانیة

Rice is the main source of calories and protein for about half of world population and also considers one of the most vital bases of employment and income for people in villages. This research presents a case study around Manzala lake, Egypt to model and produce high accuracy maps of land suitability for rice. The proposed model was used to assessment land suitability under the current situation (CS) and optimal scenario (OS). The results under CS showed that about 26% of total area is fall within the moderately suitable class and marginally suitable class (74%) class. Managing options relied on the CS assessment were projected to reduce some soil restriction factors, a fixed values were 2 dS/m for salinity, 7.8 for pH and 4 % for CaCO3.Under OS scenario showed very good results, as all of study area covered by moderately suitable compared with 26% of study area under CS. The results showed the significance of appropriate management to achieve outstand change in soil suitability and reach to agriculture sustainability.

Effect of pollution with lead, cupper, cadmium on gene expression pattern of liver GST and serum lysozymes in Nile tilapia (Oreochromis. niloticus)

Objective: This study was conducted to evaluate the influence of pollution with lead, copper, cadmium on the gene expression pattern of liver Glutathione-S-transferase and serum lysozyme in Nile tilapia (Oreochromis. niloticus). Design: Descriptive study. Fish: A Total of 120 Nile tilapia fish (Oreochromis niloticus) samples were collected from Lake Manzala, and drainage water at different localities. Procedures: Cd, Cu, and Pb concentrations residues within mid-dorsal muscle tissue, within gills, liver, and kidney were determined. Erythrocyte count, hemoglobin concentration, Packed Cell volume and other blood indices, as well as, total leukocyte count were measured. Biochemically, Alanine transaminase, Aspartate transaminase activities, total protein, creatinine, uric acid, lysozymes activity were estimated. GST gene expression was determined in the liver. Results: The results showed that Pb, Cu and Cd were bio accumulated at a higher level in the liver, kidney and gills of Nile tilapia fish (Oreochromis niloticus) from all sampling sites. The levels of the ALT and AST were increased, total protein and Albumin concentrations were decreased. Creatinine and uric acid were significantly (P≤ 0.05) increased in all groups (compared to the control group. Hematological parameters and lysozyme activity were decreased. Up regulation of the hepatic GST expression levels in Nile tilapia exposed to the heavy metals in comparison to the control value. Conclusion and clinical relevance: This study shows that lead, copper and cadmium were bio accumulated at higher concentration in liver, kidney, gills and muscles of Nile tilapia due to large industrial activities near locations of the sampling sites. Additionally, GST gene expression represents sensitive biomarker of aquatic pollution.

Incidence and molecular characterization of fungi and yeast isolated from cultured catfish and Nile tilapia

Objective: To study the incidence and seasonal dynamics of different fungi affected freshwater fishes in Lake Manzala with molecular identification of the isolated fungi. Animals: 300 Nile tilapia (Oreochromis niloticus) and 300 catfish (Clarias gariepinus). Design: Descriptive study. Procedures: Random samples of Oreochromis niloticus (O. niloticus) and Clarias gariepinus (C. gariepinus) were collected from Manzala fish farms. Clinical and postmortem examination of fish was applied. Isolation and identification of different fungi were performed by conventional methods. Furthermore, the molecular characterization of isolated fungi was carried out. Results: C. gariepinus had a higher rate of infection with different fungal species than O. niloticus. Aspergillus spp. (Aspergillus niger and Aspergillus flavus) were the most fungal isolated from the examined fishes, followed by Penicillium spp. and Candida albicans. Aspergillus spp were detected in all seasons with a higher rate in summer and spring. A. flavus, A. niger, Penicillium spp. and C.albicans isolates were amplified from both C. gariepinus and O. niloticus at the specified molecular weight using PCR. Conclusion and clinical relevance: Fungal infection affected the fish showing different external and internal lesions, all species of Aspergillus were found in all seasons with a high rate in, hot seasons, summer and spring. The Prevalence of Penicillium and C. albicans were also reported. All fungal isolates were identified on the phenotypic and molecular bases.

Inhibition of Anabaena sp. and Oscillatoria sp. Using Probiotic Lactic Acid Bacteria

Water blooms are a serious environmental problem affecting fresh and marine ecosystem. Application of probiotic bacteria has been introduced as an emerging and eco-friendly tool to regulate or inhibit cyanobacterial blooms. In the present study, we have isolated and morphologically identified cyanobacteria from El Manzala Lake. Afterward, we examined the use of probiotic lactic acid bacteria MT2 (Lactobacillus sakei) isolated from Nile Tilapia (Oreochromis niloticus) intestine in controlling Anabaena sp. and Oscillatoria sp., isolated from El Manzala Lake. Measuring chlorophyll, phycocyanin and biomass concentration were conducted in a co-culture experiment between the selected cyanobacterial isolates and probiotic lactic acid bacteria (MT2). Chlorophyll content, phycocyanin content and biomass concentration of Anabaena sp., and Oscillatoria sp., were decreased significantly in the co-culture experiment with MT2 bacteria. Also, the microscopic examinations showed that MT2 bacterium was able to lysis and degrade the selected cyanobacterial cells under microscope. We concluded that the use of MT2 (Lactobacillus sakei) is potentially effective against some cyanobacteria especially Anabaena sp. and Oscillatoria sp.

Morphological characterization and histopathological alterations of homologs Heterophyid metacercarial coinfection in farmed mullets and experimental infected pigeons

In this study, samples of farmed thin-lipped mullets, Mugil capito from Lake Manzala and wild-caught grey mullet Mugil cephalus from Alexandria were found to be infected with heterophyid encysted metacercariae (EMC), and the overall prevalence rates were 80 and 100%, respectively. The number of metacercarial infection in tail tissue was significantly higher than that recovered from trunk and head among M. capito and M. cephalus. M. capito were simultaneously infected with two morphologically different EMC that ascribed to Heterophyes and Pygidiopsis species, while M. cephalus were infected with EMC of Heterophyes species. The experimental infection of domestic pigeons (Columba livia domestica) with the recovered encysted metacercariae confirmed the successful development of two types of Heterophyid flukes: identified as Heterophyes heterophyes and Pygidiopsis genata in the small intestine of pigeons. The histopathological examination revealed that Heterophyes cyst was small, elliptical with thick wall and predominating between cardiac muscle fibres and in the lumen of atrioventricular region of the heart. Pygidiopsis species cyst appeared larger in size, rounded with thin cyst wall and prominent internal structure. Pygidiopsis species were few in the abdominal fat and prominently encysted in the internal visceral organs including wall of the stomach, kidneys and muscular tissue away. They were also deeply encysted in testes and ovaries. Interestingly, the adult flukes were demonstrated in the intestinal lumen of the experimentally infected pigeons but with minor histopathological alterations. Our findings suggest that the heterophyids EMCs in mullets have genera-specific morphological characters and may induce histopathological changes in surrounding host-associated tissues.

Effect of pollution with lead, cupper, cadmium on gene expression pattern of liver GST and serum lysozymes in Nile tilapia (Oreochromis. niloticus)

Objective: This study was conducted to evaluate the influence of pollution with lead, copper, cadmium on the gene expression pattern of liver Glutathione-S-transferase and serum lysozyme in Nile tilapia (Oreochromis. niloticus). Design: Descriptive study. Fish: A Total of 120 Nile tilapia fish (Oreochromis niloticus) samples were collected from Lake Manzala, and drainage water at different localities. Procedures: lead, copper and cadmium concentrations within mid-dorsal muscle tissue, within gills, liver, and kidney were determined. Erythrocyte count, hemoglobin concentration, Packed Cell volume and other blood indices, as well as, total leukocyte count were measured. Biochemically, Alanine transaminase, Aspartate transaminase activities, total protein, creatinine, uric acid, lysozymes activity were estimated. GST gene expression was determined in the liver. Results: The results showed that Pb, Cu and Cd were bio accumulated at a higher level in the liver, kidney and gills of Nile tilapia fish (Oreochromis niloticus) from all sampling sites. The activities of ALT and AST were increased significantly (p < 0.05), but total protein and Albumin concentrations were decreased. Creatinine and uric acid were significantly increased in all groups compared to the control group (P≤ 0.05). Hematological parameters and lysozyme activity were decreased. Up regulation of the hepatic GST expression levels in Nile tilapia exposed to the heavy metals in comparison to the control value. Conclusion and clinical relevance: This study shows that lead, copper and cadmium were bio accumulated at higher concentration in liver, kidney, gills and muscles of Nile tilapia due to large industrial activities near locations of the sampling sites. Additionally, GST gene expression represents sensitive biomarker of aquatic pollution.

Incidence and molecular characterization of fungi and yeast isolated from cultured catfish and Nile tilapia.

Objective: To study the incidence and seasonal dynamics of different fungi affecting freshwater fishes in Lake Manzala as well as molecular identification of the isolated fungi. Animals: 300 Nile tilapia (Oreochromis niloticus) and 300 catfish (Clarias gariepinus). Design: Descriptive study. Procedures: Random samples of Oreochromis niloticus (O. niloticus) and Clarias gariepinus (C. gariepinus) were collected from Manzala fish farms. Clinical and postmortem examination of fish was applied. Isolation and identification of different fungi were performed by conventional methods.Furthermore, the molecular characterization of isolated fungi was carried out. Results: C. gariepinus had a higher rate of infection with different fungal species than O. niloticus. Aspergillus spp. (Aspergillus niger and Aspergillus flavus) were the most fungal isolated from the examined fishes, followed by Penicillium spp. and Candida albicans. Aspergillus spp were detected in all seasons with a higher rate in summer and spring. A. flavus, A. niger, Penicillium spp . and C.albicans isolates were amplified from both C. gariepinus and O. niloticus at the specified molecular weight using PCR. Conclusion and clinical relevance: Fungal infection affected the fish showing different external and internal lesions, all species of Aspergillus were found in all seasons with a high rate in, hot seasons, summer and spring. The Prevalence of Penicillium and C. albicans were also reported. All fungal isolates were identified on the phenotypic and molecular bases.

Evaluation of Water Quality on TNF- α and IL- 1 Immune Genes in Oreochromis Niloticus Fish at El Manzala Lake in Egypt

Lake Manzala is known to be from the most significant sources of inexpensive different fish species for human consumption in Egypt. The Lake receives pollution from various sources; domestic wastewater, industrial wastewater, and agricultural drainage directly without any treatments, which lead to many environmental disorders. The following research was conducted for lake water quality evaluation and how it impacts the expression of Tumor necrosis factor- α (TNF- α) and Interleukin-1 (IL- 1) immune genes. Sampling was done seasonally from October 2015 to September 2016, where water and fish samples were collected from 4 locations in El Manzala Lake after mixing with Bahr El Baqr drain (sampling points were 4 km apart from each other). Average values of dissolved oxygen, chemical oxygen, and biological oxygen demand were 6.7 mg O2/l, 139.4 mg O2/l, 92.8 mg O2/l, respectively. For the Nitrogen group, the average concentration of ammonia, nitrite, and nitrate was 0.7 mg/l, 0.38 mg/l, and 0.38 mg/l, respectively. The average records of total bacterial count and total and fecal coliform suggesting high loads of contaminants, particularly in sampling sites close to Bahr El Baqr drain. The relative occurrence of cyanobacteria in water samples was influenced by increasing lake water temperature. The expression of the immune genes for TNF- α and IL- 1 in Nile Tilapia fish liver was confirmed by RT-PCR. The results showed up-regulation of these genes in the liver of Nile Tilapia fish, especially in warm seasons (summer, late summer). TNF-α and IL- 1 level in Nile Tilapia fish could be used as early diagnostic indicators to different environmental events and also are helpful and reliable bioindicators in estimating pollutants of the aquatic environment. High levels of pollution in El Manzala Lake were recorded in this study that may proceed with health risks to a human. Therefore, the Lake needs proper policies to protect and preserve its ecological integrity and biodiversity.

Bio - Economic study of the potential development of fisheries in Lake Manzala

The research aimed to study the determinants of fish production in Manzala Lake, study the seasonal movements of fish species, and show that the area of the water area of Manzala Lake did not exceed 0.7% of the total water area of Egyptian fisheries, but it contributes about 16% of the total Egyptian fish production, respectively, and about 14 . 2% of the total Egyptian fish income. It turns out that the annual fish production in Manzala Lake is directly related to the numbers of boats, the numbers of fishermen and the fish prices, and inversely with the average annual yield of the fisherman. It is clear that the fish production in Manzala Lake fisheries exceeds the seasonal average for the fall semester from the seasonal average for the rest of the seasons of the year to being the breeding and spawning season for the fish as well as the autumn months are actual fishing months where the hunter stays for long periods in the lake, while the average for the spring is the lowest for the rest of the seasons. The necessity of continuous follow-up in the treatment of incoming agricultural wastewater for the lake, and the continuous cleansing of the Bogus lake opening and guarding it from the thief of fry, with continuous review of the maximum allowed number of fishing boats operating in the lake according to technical and economic bases.

Evaluation of bacterial quality of Oreochromis niloticus samples of Lake Manzala, Egypt

The present study aimed to investigate bacterial quality of tilapia fish (Oreochromis niloticus) and evaluate the hygienic health hazard of fish contaminated with some food borne pathogens. Bacteria were isolated from intestine, gills and flesh of Oreochromis niloticus collected from Lake Manzala during two seasons; winter and summer, 2017. Microbiological studies was applied for all samples as total viable bacteria, total coliform, faecal coliform, faecal streptococcus and examined for the presence of Pseudomonas sp. Results show that total viable bacterial count mean was highest in intestine 222 x 104 CFUg-1 in summer. Total coliform count mean was highest in intestine 425 x 103 CFUg-1 in summer. Faecal coliform count mean was highest in gills 90 x 102 CFUg-1 in summer. Faecal streptococcus detected in fish organs only in summer. P. aeruginosa count mean was highest in intestine 185 x 102 CFUg-1 in summer. Molecular identification of suspected colonies was as DNA extraction, PCR technique using ISSR protocol and sequencing, using the nucleotide sequences of the genes for 16S rRNA revealed different strains of Pseudomonas aeruginosa. All isolates were tested for resistance to 10 groups of antibiotics namely Tetracycline (10μg), Gentamicin (10μg), Ampicillin (10μg), Trimethoprim/Sulphamethoxazole (25μg), Vancomycin (30μg), Erythromycin (15μg), Ciprofloxacin (30μg), Chloramphenicol (30μg), Amoxicillin (10μg) and Rifampicin (5μg) using Kirby-Bauer disc diffusion method. The results showed high frequency of multi-drug resistance to many antibiotics, particularly penicillin, ampicillin and chloramphenicol. Therefore this fish species caught from the Lake Manzala may pose health hazards to human and the whole ecosystem.

Bioaccumulation of Chromium by Autochthonous Bacteria Associated With The Heavy Metal- Resistant Halophyte Arthrocnemum macrostachyum

ARTHROCNEMUM macrostachyum is a halophyte naturally growing on Manzala Lake shoreline of Egypt and able to tolerate and accumulate heavy metals. The use of metal-resistant rhizobacteria is an important technology to improve the tolerance capability of the halophytes in metal-polluted environments. A total of 33 bacterial isolates were obtained from the root system of A. macrostachyum and screened for resistance to 1.25 and 12.5mM of Cr(VI) in plant-based culture medium prepared from the halophyte shoot juice. The six most tolerant isolates were identified based on cell morphology and API microtube profiles. Those isolates were found closely related to Bacillus lentus, Burkholderia cepacia, Raoultella ornithinolytica and Providencia retgeri indicated on the online database. Among the strains tested for their ability to accumulate chromium, Bacillus lentus was the most effective with an average accumulation percentage of 17.8, Providencia retgeri ranked thereafter (15.1%). Bacillus circulance was the least with a negligible accumulation level of 0.5%. The biosorption rate of the heavy metal was contact time- and bacterial strain-dependent. Again, Bacillus lentus showed the highest uptake capacity of 32.8mg g-1, a parameter that positively correlated with contact time (r= 0.865), this was not the case with Burkholderia cepacia where the correlation was negative (r= – 0.811). When introduced into an aqueous solution of 25mg L-1 Cr(VI), Burkholderia cepacia was the superior in Cr(VI) reduction (86.7%), while Bacillus circulance failed to reduce the heavy metal. The pH 5.5 was the most favorable for bacterial Cr accumulation which proportionally decreased as the acidity of the solution increased. This study provides more understanding of the significant contribution of the heavy metal-tolerant microbiome to improve the metal remediation efficiency of halophytic plant covers of stressed environments.

Impacts of physicochemical and heavy metal parameters on infestation level of the monogeneans, Quadriacanthus spp. infesting Nile catfish, Clarias gariepinus of different water localities in Nile Delta, Egypt.

Fish parasites can be used as bio-indicators to evaluate pollution degree in aquatic ecosystems. Limited research has, however, investigated the potentiality of these parasitic worms to tolerate various environmental factors. This study, therefore, investigated whether the gill, Quadriacanthus monogenean parasites of Bagrus bajad Forskål, 1775 are potential bio-indicators of aquatic ecosystem health. The seasonal differences in prevalence, mean intensity and abundance of Quadriacanthus species of Clarias gariepinus varied between each other and between the three localities. Most Quadriacanthus species exhibited their highest prevalence, mean intensity and abundance in Spring and/or Summer and their lowest values in Autumn and/or Winter. The seasonal differences in prevalence were significant for Q. kearni and Q. clariadis while a significant difference in the mean intensity between different seasons was recorded only for Q. aegypticus. Also, seasonal differences in the abundance were highly significant for Q. aegypticus and significant for Q. kearni. The total dissolved solids, Chlorides, Sulphate, Sodium, Cadmium and Lead were higher at Manzala Lake than standard permissible limits. The pH has significant correlations with the infestation levels of all Quadriacanthus spp. Dissolved oxygen showed a highly significant positive correlation with the mean intensity of Q. clariadis and a significant positive correlation with the abundance of Q. clariadis. Iron was the only heavy metal to record a significant positive relationship with the mean intensity of Q. kearni. It is noteworthy that Quadriacanthus species were found to have a noticeable ability to resist the effect of hazardous concentrations of many physicochemical and heavy metals parameters. Therefore, it is highly recommended that these monogeneans could be regarded as bio-indicators for water quality.

Molecular characterization and expression analysis of hepc1 and hepc2 in three tilapia species collected from Lake Manzala

BackgroundAntimicrobial peptides were examined as an evolutionarily preserved component of the innate immune response and identified as a vital first-line defense against a broad spectrum of pathogens in fish. The objective of this study was to investigate the molecular characterization and expression analysis of hepc1 and hepc2 in three strains of tilapia species infected naturally in Lake Manzala.ResultsThe results revealed that the alignment of nucleotide sequences including cDNA and deduced amino acid sequences showed that hepcidin 1 in Sarotherodon galilaeus has four genotypes due to SNPs in codon 34Gln (CAG)/Leu (CTG) and codon 36Glu (GAA/GAG). Regarding hepcidin 2 gene, different genotypes were detected in Tilapia zillii and Sarotherodon galilaeus due to SNPs in codons 19Met (ATG)/Ile (ATT), 57Pro (CCA)/Ser (TCA), and codon 14Leu (CTT / CTC). Hepcidins 1 and 2 coding region sequences in three tilapia species deposited to GeneBank and phylogenetic analysis indicated that tilapia species are more similar to each other and closely related to Sea perch. On the other hand, the expression levels of hepc1 and hepc2 genes were over-expressed in different tilapia tissue species (hepc1 in Sarotherodon galilaeus and hepc2 in Tilapia zillii).ConclusionsThe results concluded that the hepcidin 1 and 2 genes showed constitutive expressions in most of tested tissues and have a very similar three-dimensional structure as well as mature peptides which mean that these genes are highly conserved within the species examined.

Current status of Liza ramada (Risso, 1810) (Mugilidae) caught by trammel net (Ballah) at El-Gamil region, Manzala Lake, Egypt

Liza ramada, the target species caught by trammel net (Ballah) at El-Gamil region, north of Lake Manzala, is studied to estimate the life history parameters by using length–frequency data of 842 specimens. The life span was estimated as 4 years. It exhibited a negative allometric growth (b=2.94). The von Bertalanffy growth parameters were L∞= 30.45cm, K= 0.48 yr−1 and t0 =-0.339 yr−1 with a derived growth performance index of O′ =2.6 .The mean annual instantaneous total, natural and fishing mortality coefficients were 1.47, 0.71and 0.76/year, respectively. The exploitation rate was estimated as 0.52. The probability of capture ensured that 50 percent (Lc) of the fish caught was estimated at length 12.18 cm which is 31.2% lower than the length at first sexual maturity (17.7 cm) and lower by 40.1% than the estimated Lopt value (20.4 cm). This result reflects the smaller mesh sizes of the inner layer of nets used by fishermen. Therefore an urgent recommendation should be applied to prevent the illegal fishing gears, increase the mesh sizes especially for the inner layer of trammel net used as well as improving the quality of water discharged into the lake to increase the yield per recruit of Liza ramada, protect fish stocks and to secure a profitable fisheries and optimum catch efficiency for the future.

Land use/cover and eco-toxicity indices for identifying metal contamination in sediments of drains, Manzala Lake, Egypt

Six heavy metals in three main drains along the East Nile Delta were estimated to assess the environmental risk and employ land use/cover map of each drain. Composite sediment samples (n = 3) were collected from each drain. The elements were analyzed by Atomic Absorption Spectrophotometer. The order of metal ions in the sediments of three drains of Manzala lake take the following order: Fe > Co > Ni > Cr > Cd > Pb in El-Serw drain, Fe > Ni > Co > Cd > Cr > Pb in Hadous drain and Fe > Cd > Ni > Co > Pb > Cr in Bahr El-Baqar drain. Studied Pollution indices indicate that drains discharged into Manzala Lake are mostly contaminated by metals. Geo-accumulation index showed contamination by Cd in all sites especially in site 13 of Bahr El-Baqar drain and low values to others. The mean probable effect level quotient showed percent of 21% in Hadous and El-Serw drains and 73% probability of being toxic in Bahr El-Baqar drain. The mean effect range median quotient also showed 21% in Hadous and El-Serw to 49% probability of being toxic in Bahr El-Baqar drains. Index of anthropogenicity impact indicate that the man-made activity either agricultural, industrial or fisheries impacted in the appearance of metal ions in the following sequence; Cd > Co > Pb > Ni > Cr. Hazard severity according to hazard quotient and modified hazard quotient of Ni and Cd take the following sequence; El-Serw < Hadous < Bahr El-Baqar drains. For Cr is; Hadous < Bahr El-Baqar < El-Serw and Pb is; Hadous < Elserw < Bahr El-Baqar drains. According to contamination severity index showed low for Pb, Ni and Cr and severe for Co and Cd which take the sequence of; Bahr El-Baqar > El-Serw > Hadous.

Molecular Detection of Some Virulence Genes in Aeromonas Species Isolated from Fishes and Water of Manzala Lake

In a view of increasing the role of Aeromonas spp. in fish and human diseases, the present wok was conducted to assay the presence of six virulence genes using PCR in Aeromonas species isolated fromfishes and water of Manzala Lake. A total of 200 fish samples comprising 100 Oreochromis niloticus fish, 100 Mugil cephalus fish and 50 water samples were collected from El Gamil region in Lake Manzala. A total number of 258 isolates belonging to Aeromonas spp. were recovered from fish and lake water samples and they were biochemically identified into 4 biotypes. PCR assay of 15 representatives, biochemically confirmed Aeromonas spp. isolates showed that they were genetically confirmed belonging to genus Aeromonas based on specific16S rRNA gene sequence. Virulence properties of the 15 representative strains showed that the majority of the examined strains carried one or more virulence genes. A significant 5 virulence gene have been found in the tested Aeromonas isolates. The frequencies distribution of these genes wasaero (100%), act (20%), ahcytoen (13.33%), lip (13.33%), alt (6.67%). Meanwhile, Haemolysin (hly) gene could not be detected in any of examined Aeromonas isolates.