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Minia University (2004)

Ecological Studies on Algal Communities in Relation to Environmental Factors at El-Kharga Oasis, New Valley, Egypt

Ahmed, Gamal El-dein Gdarib.

Titre : Ecological Studies on Algal Communities in Relation to Environmental Factors at El-Kharga Oasis, New Valley, Egypt

Auteur : Ahmed, Gamal El-dein Gdarib.

Etablissement de soutenance : Minia University

Grade : Master of Science (MS) Botany 2004

Résumé
Physicochemical water analysis and algal investigations of 15 selected water bodies in wells (cold and hot), agricultural drainage canals, rice fields and sewage oxidation ponds at El-Kharga Oasis, New Valley, Egypt have been conducted monthly during the period June 1998- May 2000. The studied areas were located in the city El- Kharga and the surrounding areas extending from El- ’’ Sherka village about 14 km to the north of the city till the village Boulak about 30 km to the south. The results of study revealed that : l - Water wells were characterized by the highest mean water temperature compared to the other water bodies studied whereas mean values of the other parameters studied were the lowest except for the cations ; Na’, K, Ca and Mg which were slightly higher than that recorded in rice fields. 2- Agricultural drains were characterized by the lowest mean water temperature and moderate pH, alkalinity, COD, K+, Ca” and Mg’. Concentrations of Na+ and chloride were the highest among all the studied water types indicating elevated water salinity. 3- Rice fields were almost similar to water wells, however, they had higher values of pH, alkalinity and nitrate- N than water wells. On the other hand, It concentrations of Na+, K+, Cam and Mg were lower in water of rice fields than in wells. Mean water temperature was higher than that recorded in the other water types except water wells. 4- Sewage oxidation ponds were characterized by low mean water temperature and highest values of pH, alkalinity, COD, nitrate — N, phosphate- P and K+, Ca’ and Mg+. Electrical conductivity and concentrations of t a+ were moderate. A& 5- Throughout the period of study, a total of 233 taxa have been recorded of which 63 were cyanophytes, 69 chlorophytes, 19 euglenophytes, 2 pyri-hophytes and 80 bacillariophytes representing 27.04%, 29.61%, 8.15%, 0.86% and 34.33% of the total number of taxa respectively. 6- Taxa that attained large frequency of occurrence were, Chroococcus turgidus, Oscillatoria an/malls, O. subbrevis, 0. terebtriforn is, Closterium hanumeri, Cosmariuin laevae, Denticula tennuis, Gomphonerna parvulurn, Nitzschia thermalis and N. umbonata. 7- The highest number of taxa was recorded in agricultural drains. Sewage oxidation ponds had slightly smaller number of taxa than in agricultural drains. The least number of taxa was recorded in the hot wells. 8- Diversity of species agreed with the number of taxa being the highest at agricultural drains and the lowest at hot water wells.

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Page publiée le 1er janvier 2021