Zoosporic fungi and fungus-like organisms in the Siemianówka dam reservoir

Abstract: The occurrence of fungi in the Siemianowka dam reservoir and in the river Narew downstream and upstream of the reservoir was investigated, during the spring, summer and autumn months, taking into consideration many physicochemical factors of water. Phytoplankton chlorophyll a content was also determined. Eighty-seven fungal species, including 71 fungus-like organisms (Straminipila) and 16 species of true fungi were identified. Most species were found in the river Narew upstream of the reservoir, the fewest inside it. The latter finding can be correlated with cyanobacterial blooming recurring every year. The greatest number of species developed in the spring months, the smallest in the summer period. The surface layer of the reservoir was poorer in species than its deeper layers. Moreover, 6 rare species were detected, including Aphanodictyon apiculatum which is recorded for Poland for the first time.