Effect of some Environmental Factors on the Distributions and Chlorophyll Contents of Fresh Water Phytoplankton of the River Nile before El-Qanater El-Khairia Barrage, Egypt.

INVESTIGATIONS were carried out on the seasonal variations, ….. biodiversity and chlorophyll contents of phytoplankton in relation to physico-chemical parameters of the River Nile water before El-Qanater El-Khairia barrage during two successive years (from summer 2006 to spring 2008). The detected phytoplankton community consisted of 176 species in 62 genera of six systematic algal divisions. Chlorophyta (42.05%) recorded the highest population followed by Bacillariophyta (40.91%), Cyanophyta (9.65%) and Euglenophyta (5.11%). Pyrrophyta and Xanthophyta were less dominant. Chlorophyta, Bacillariophyta and Cyanophyta were responsible for the remarkable fluctuations in the phytoplanktonic picture of the investigated water. The highest number of taxa of all divisions was recorded in summer 2006. These may due to the highest recorded values in K+, Cl-, NO3-, and PO4-3 with lowest values in the electrical conductivity (E.C), total dissolved salts (TDS), HCO3- and CO32- during this season. Algal productivity (as number of individuals L-1) attained its highest value during summer 2007, while its lowest value was recorded in winter 2008. These may correlated to the highest recorded values of temperature, silicate and bicarbonate in association with complete depletion in Phosphorus and Carbonate values in the same season. The lowest number of taxa and the total algal productivity (as number of individuals L-1) of all divisions were recorded during winter 2008. This was positively correlated with the relative increased in Sulphate, Carbonate, Magnesium and Phosphate concentrations during winter 2008.This may attribute to death and decomposition of aquatic microorganisms in this season. Summer 2006 showed maximum values in both Shannon-Weaver diversity (H) and species richness (D). There more or less positive correlations between the fluctuations of total chlorophyll contents (ug L-1) and those of total