الفهرس 
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Abstract
Cyanobacterial winter bloom occurred in Port-Said at the northern part of Egypt causing an unpleasant taste and odor of drinking water and the frequent clogging of filters in the drinking water treatment plant were the primary problems that trigger this study. The objectives were to explore the changes in cyanobacterial community structure at different sites and to explore the primary factors affecting such structure. Samples of water and water column algae were collected from the Port-Said freshwater canal and sites along the Rosetta branch of the Nile River in Kafr El-Zayat, Edvena and Rosetta from September 2007 to March 2009. Variations in floristic composition, phytoplankton communities and water characteristics were determined. Different ecological parameters exhibited seasonal variations with small changes among different sites. Among the identified species of Cyanophyta, Microcystis aeruginosa, Oscillatoria brevis and Oscillatoria princeps recorded the highest cell counts. For Microcystis aeruginosa, the maximum cell counts were recorded in November 2008 and January 2009 at the Edvena site; maximum values of Oscillatoria brevis were recorded in January 2009 at the Kafr El-Zayat site, and maximum values of Oscillatoria princeps were recorded in January 2009 at the Rosetta site. A canonical correspondence analysis (CCA) of physicochemical parameters and cyanobacterial counts indicate that the maximum counts were positively correlated with TDS, nitrate, ammonium and phosphate.