Seasonal fluctuations of freshwater fungi in river Nile (Egypt).

The seasonal fluctuations of aquatic fungi were studied over 24 water sample collected monthly between May 1979 and April 1981 from the River Nile near Assiut (about 375 km, south from Cairo, Egypt). The richest periods in aquatic fungal genera and species were September--December 1979, January--March, October--December 1980, and January--April 1981. These periods represent low or moderate temperature months. The poorest periods were May--August 1979, April, May, July, August and September 1980 which are almost summer months. Twenty-nine species and one variety of Olpidiopsis saprolegniae which belong to ten genera of aquatic fungi were collected during this investigation. Three genera were of high seasonal occurrence (19-24 months) namely: Achlya, Saprolegnia and Dictyuchus. Three other genera were of moderate seasonal occurrence (6-11 months) namely: Isoachlya, Leptolegnia and Pythium. The rest of genera were of low or rare seasonal occurrence.