B. Papp szerk.: Studia Botanica Hungarica 35. 2004 (Budapest, 2004)

Gönczöl, János; Révay, Ágnes: Aquatic Hyphomycetes in two streams differing in discharge and distribution of leaf litter

in determining fungal communities were both important, but not to the same degree (GÖNCZÖL et al. 2003). The results of canonical correspondence analysis suggested that altitude, water hardness and conductivity were the major factors correlated with the distribution of individual species. At the same time we still know little about the composition of conidial communities and conidial concentrations in low-order, small streams in the Morgó stream system. There are little data in the literature on conidial concentrations, amount of allochthonous substrates and discharge in small streams. It is well known that the major peak in conidial numbers in forested streams in temperate climates coincides with leaf fall (IQBAL and WEBSTER 1973, BÄRLOCHER and ROSSET 1981, SHEARER and WEBSTER 19856). However, we know little how stream hydraulics affects the structure and quantity of substrates and the spore concentrations in stream water. Therefore the objectives of this study were: 1 ) to survey the structure and estimate quantity of the leaf litter in two second-order tributaries differing in hydrological features in the Morgó stream system, and 2) to analyse the species composition and conidial numbers of aquatic hyphomycetes in these small streams. MATERIALS AND METHODS The study was conducted on the Deszkametsző and Bagolybükk streams, two second-order tributaries of the Morgó stream (Börzsöny Mts, Hungary). Two sampling sites were chosen in each stream (Dl, D2, Bl, B2 in Fig. 1). Five water samples (5x 150 ml) were taken at each sampling site on 21 April, 25 October and 29 November 2001. Immediately after collection the water samples were passed through Whatman Isopore polycarbonate membrane filters (25 mm diam, 8 pm pore size) using pneumatic pumps (Antlia Pressure Filtration System, Schleicher & Schuell, Dassel, Germany). The conidia trapped on the filters were stained with cotton blue in lactic acid. The entire surface of each filter was thoroughly scanned at 250-400x magnification and the conidia were identified and counted. The number of conidia per litre of water was then calculated. The stream sites were characterised by geographical and some physicochemical parameters. Water temperature, pH, conductivity, total hardness and discharge were measured in the field on each sampling occasion (Table 1). Discharge was calculated by measuring the current velocity with a propeller-type current meter (FP 101 Flow Probe, Global Water Instrumentation, USA). The species composition of the leaf litter in the streambed was estimated by randomly taking 500 pieces of leaves collected in October and November from ca 300-500 m long sections of the streams above each sampling site. The leaves were identified, counted and their relative frequencies were calculated (Table 2). The /-test was used for testing differences in water chemistry and in total number of species between streams and for comparison of conidial concentrations at the sites of each stream.