الفهرس 
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Abstract
The study aims to assess the water quality of the Nile River in Damietta region with the use of numerous statistical analyses, in addition to the determination of the riverine protozoa community dynamics and employment of which as bio-indictors of the Nile River water quality.
The environmental investigations after the monthly analysis of 32 physicochemical parameters along one year from February 2016 to January 2017 at six different sampling sites, revealed that about 70% of the total variance in observations was explained by five main influences using Factor analysis; seasonal fluctuation, agricultural activities, organic matters, heavy metals, and erosion factor. Cluster analysis distributed the sites into two groups, the first (Sites IV and VI) of lower quality attributed to untreated drainage and dense agricultural discharges, the second (Sites I, II, III and V) with better quality. Only 11 parameters were necessary for distinguishing temporal variations according to Discriminant analysis, while only seven parameters were responsible for spatial variations. Site VI was showed the highest WQI values, which generally ranged between 12.73 and 33.73. According to these values, the Nile River Damietta branch represents a good to an excellent source of drinking water for entering secondary treatment.
The free-living protozoa community recorded a number of 54 species along the Nile River in Damietta region distributed into six main protozoa phyla (Amoebozoa, Choanozoa, Heliozoa, Cercozoa, Myzozoa, Ciliophora). Ciliophora phylum recorded the highest richness (30 species). Shannon Diversity Index had an absolute value of 3.13 bits. The protozoan abundance showed a high density with an average total abundance of 1089 Cells /l, as well as the population biomass data that showed significant variation with a mean total of 588.3 μg /l. Cluster analysis resulted in the distribution of protozoan species into three groups according to their dominance revealing the most dominant species (Paradileptus elephantinus). Spearman’s test for biological indices resulted in a significant negative effect of aluminum, fluoride, and turbidity on abundance and biomass, and positive effect of dissolved oxygen and potassium on biomass. And finally, multivariate analysis resulted in the distribution of protozoa community on three different types of habitats along the river (higher runoffs, higher temperature, and higher dissolved salts).