Author(s): Mohamed Saad Abd El-Karim, Abeer MA Mahmoud

Abstract: Lake Nasser plays an important role in the local and national economy. Phytoplankton is the main base for organic matter production for different consumers in Lake Nasser. The present study investigated the variation in phytoplankton biomass, chlorophyll a, and biochemical contents, lipid, protein and carbohydrates. The samples were collected from three different regions, the main channel and two Khors, Tushka and Dahmeit in mid autumn-2014 and late spring-2015. Chlorophyll a, carbohydrate, lipid and protein levels were non-significantly differed among the three regions of the lake (P = 0.13). Total protein constitutes the major part of the biochemical contents of the phytoplankton while total lipid constitutes the minor one. In general, average chlorophyll a, carbohydrate, lipid and protein were 4.27 µg/l, 2.89 mg/l, 0.2 mg/l and 38.91 mg/l, respectively, in the main channel, 7.86 µg/l, 1.74 mg/l, 0.16 mg/l and 30.68 mg/l, respectively, in Khor Tushka, whilst they were 4.2 µg/l, 1.34 mg/l, 0.28 mg/l and 39.36 mg/l, respectively, in Khor Dahmeit. Results of the principle components analysis and Spearman correlation matrix indicated that responses of biochemical composition and chlorophyll a to the changes in nutrient concentrations were dissimilar depending on the location and time of sampling which indicated that, in addition to nutrients, many other factors regulate chlorophyll a and biochemical contents in Lake Nasser. The regression analysis revealed a lack of correlation between chlorophyll and both reactive phosphorus and total inorganic nitrogen (TIN) in Khor Dahmeit, whereas slight correlations were found with PO4 in the main channel and Khor Tushka. PO4 significantly explained 22% (P = 0.019) and 11% (P = 0.008) of the observed chlorophyll a variability in Khor Tushka and main channel, respectively.

Pages: 463-473  |  1352 Views  97 Downloads

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