B. Papp szerk.: Studia Botanica Hungarica 29. 1998 (Budapest, 1999)

Gönczöl, János; Révay, Ágnes: Aquatic Hyphomycetes in a tributary of the Morgó stream, Börzsöny Mts, NE Hungary

Spatial and temporal distribution of conidial communities of aquatic hyphomycetes of the Morgó stream system has been studied largely in the main channel of this stream system (GÖNCZÖL 1975, RÉVAY and GÖNCZÖL 1990, GÖNCZÖL and RÉVAY 1993, GÖNCZÖL et al. 1999, GÖNCZÖL and RÉVAY 1999). Little is known, however, about the aquatic hyphomycetes of the tributaries. The main goal of this study was to compare conidial communities of aquatic hyphomycetes of a tributary and the main channel of the Morgó stream. From the comparison of aquatic fungal communities of sites different in their water chemistry and/or riparian vegetation was hoped to get further data about the ecological requirements of individual species. MATERIALS AND METHODS Sampling site and technique The study was conducted at the Csömöle stream, a second order tributary of the Morgó stream. This is a small, generally 1 m wide and 10-20 cm deep, slowly flowing and slightly meandering stream of rocky bed and with low but fairly constant discharge. One sampling site (Site Cs) was chosen approximately midway along the stream (Fig. 1). Water temperature, conductivity, pH and total hardness were measured in the field on every sampling occasion. The measuring methods and instruments were the same as those published earlier (RÉVAY and GÖNCZÖL 1990). Two water samples (250-250 ml) were taken on the following dates: 9 April, 5 June, 15 August, 25 October, 5 December 1997 and 21 January 1998. Immediately after collection the water samples were passed through Whatman Isopore polycarbonate membrane filters (25 mm diam, 8 p.m pore size) using pneumatic pumps (Antlia Pressure Filtration System, Schleicher and Schuell, Dassel, Germany). The conidia retained on the filter surface were stained with cotton blue in lactic acid. The entire surface of each filter was thoroughly scanned and at 250-400x magnification the conidia identified and counted. The number of conidia per litre of water was then calculated. The species composition of the leaf litter in the stream bed was analysed. 500-500 leaves were randomly collected from the stream around the sampling site on 25 October 1997 and on 6 November 1998. The leaves were identified, counted and their relative frequencies calculated. To compare the aquatic hyphomycete communities detected in the Csömöle stream and at six sites of the Morgó stream studied earlier (GÖNCZÖL et al. 1999) two similarity indices were calculated. Sörensen's index = 2c/a+b * 100, with a+b = sum of the number of species of two sites, and c = number of species in