Microbiol. Res. (1996) 151, 149 -156 Aquatic phycomycetes Microbiological Research © Gustav Fischer Verlag Jena recovered from Aswan High Dam Lake [AHDL] Farida T. EI-Hissy, A. M. Moharram, Soad A. EI-Zayat, M. S. Massoud Botany Department, Faculty of Science, Assiut University, Assiut, Egypt. Accepted: October 7, 1995 Abstract Twenty five identified and four unidentified species belong- ing to eleven genera of aquatic phycomycetes were recover- ed from one hundred and thirty surface water samples which were collected mainly from Aswan High Dam Lake (100 samples) in addition to few samples from Aswan reservoir (10 sample) and the main stream of the River Nile at Aswan (20 samples) during the period from January to June, 1992. The richest water samples in aquatic phycomycetes species were those characterized by relatively low tem- peratures (15.9 QC - 20.3 QC) and pH ranged between 7.4-8.3. The poorest samples were characterized by relatively high temperature (20.6 QC - 33.1 QC). pH values fluctuating between 6.3 and 9.2, dissolved oxygen varying from 4.5 to 10.6 mg/L, total soluble salts ranging from 149 to 303 mg/L and the organic matter content between 2.0 and 51.1 mg/L. Saprolegina and Pythium were the most frequent aquatic fungal genera recovered during this investigation whereas Aphanomyces, Dictyuchus, Pythiop sis, Leptomitus, Allomyces and Blastocladiopsis were less frequent. Introduction Several investigations were conducted concerning the aquatic phycomycetes from different water habitats allover the world (e.g. Petersen 1910, Lund 1934 in Denmark; Waterhouse 1942, Dick 1972, 1973, Wil- loughby et al. 1983 in the United Kingdom; Johnson 1974, Johnson et al. 1975 in Iceland; Schaperc1aus 1935, Jacobsen 1981, EI-Hissy 1994 in Germany; Ziegler 1958, and Klich and Tiffany 1985 in USA; Barr 1969 in Canada; Meshcheryakova 1979 in the Corresponding author: F. T. EL-Hissy former Soviet Union; Suzuki and Hatakeyama 1960 in Japan; Dayal and Tandon 1962, 1963, Srivastava 1967, Hasija and Batra 1978 in India, Rattan et al. 1978,1980, Ismail et al. 1979 and AI-Saadi et al. 1979 in Iraq. In Egypt, in spite of several researches were made dealing with the occurrence and distribution of the aquatic fungi in the water habitats (EI-Hissy 1974; EI-Hissy and Khalli11989, 1992, EI-Hissy et al. 1989, 1992, EI-Nagdy and Abdel-Hafez 1990), the most important water impoundment (source) which is known as Aswan High Dam Lake (AHDL) was not yet studied. Therefore, the aim of this investigation was to study the occurrence and distribution of aquatic phycomycetes principally from Aswan High Dam Lake (AHDL) besides Aswan reservoir and the main stream of the River Nile at Aswan as repre- sented by few samples. Materials and methods Collection of water samples: One hundred and thirty surface water samples were collected during this investigation. The majority of these samples (100 water samples) were collected from Aswan High Dam Lake (AHDL) in addition to some samples collected from Aswan reservoir (10 samples) and the River Nile in the area from Aswan to Edfo city (20 samples) as shown in Fig. 1,2 and 3. These samples were taken using sterile glass bottles of one liter capacity which contained a number of sterile sesame seeds for baiting the fungal propagules (zoospores or hyphal fragments of the aquatic fungi). Temperature, pH value, dissolved oxygen, total soluble salts and organic matter contents of the Microbiol. Res. 151 (1996) 2 149