الفهرس 
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Abstract
Manzala lake is an open system; it thus receives a high population of bacteria originating from many different inlets surrounding the lake. To study bacterial population in water and fish of the southern area of the lake, water and fish samples were taken in summer and winter. For all bacterial counts performed (total aerobic, total coliform, Fecal coliform, E. coli and enterococci) differences were observed in water and fish samples, total aerobic bacteria in water of fish farm was exhibited the highest values in summer and winter samples. Randomly some of the isolates were identified as the following genera: Citrobacter, E. coli, Edwardsiella, Enterobacter, Hafina, Klebsiella, Proteus, Providancia, Enterococcus faecalis, and E. faecium. The results, with regard to public health, suggest that the occurrence of these bacteria in the lake and fish reflects the need for a practice for fish growers in the lake and stresses the need for establishing a safety limit for fish to be harvested for marketing and human consumption. Some of the isolates from water, fish skin and fish gut samples were identified as the following genera: Citrobacter, Edwardsiella, Enterobacter, Hafina, Klebsiella, Proteus, Providancia, and the species E. coli, Enterococcus faecalis, and E. faecium. It is evident from the results that bacterial quality of the fish organs reflects the bacteriological condition of water in which they live, especially fish guts and the skin surface. When studying correlation between the measured parameters of Manzala lake water and the bacterial content it was found that the implication is that strong relationships were found for the total aerobic bacteria, total coliform, fecal coliform, E. coli and Enterococci densities in water samples and salinity percentages . It could be concluded that the increment in the bacterial content has contributed to the increment in BOD5 measurements. Data showed a negative linear relationship between bacterial content and nitrate concentration in water samples, that is, bacterial count decrease as nitrate values increase. It appeared that there is a positive linear relation between phosphorous concentration and bacterial content of different water samples, that is, the bacterial densities increase as phosphorous increase and there were strong relationships found for each of total aerobic bacteria, total coliform, fecal coliform, and E. coli densities in water samples and the corresponding phosphorous values and there is a positive linear relation between the twelve values of bacterial densities and lead concentrations in water samples. Results also indicated that there is a positive linear relation between copper concentration and fecal coliform content of different water samples.