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
Studia bot. hung. 35, pp. 45-58, 2004 AQUATIC HYPHOMYCETES IN TWO STREAMS DIFFERING IN DISCHARGE AND DISTRIBUTION OF LEAF LITTER J. GÖNCZÖL and Á. RÉV AY Department of Botany, Hungarian Natural History Museum H-I476 Budapest, Pf. 222, Hungary; E-mail: gonczol@bot.nhmus.hu, revay@bot.nhmus.hu Aquatic hyphomycete conidia in transport at four sites in two second-order streams in the Börzsöny Mountains, Hungary were analysed in April, October and November. The streams differed in discharge, water chemistry, distribution and composition of leaf litter in the streambed. Both the conidial concentrations and the numbers of aquatic hyphomycete species were significantly higher in the moderately hardwater, slow-flowing Deszkametsző stream than in the softwater, fast-flowing Bagolybiikk stream. Opposite patterns of changes in conidial concentrations in a downstream direction were obtained in the two tributaries. Conidial numbers and discharge changed in a contrary direction in both streams. The relatively high conidial concentrations (more than 20,000 conidia L" 1 ) appear to be a general pattern in low-order streams with slow-flowing shallow water, low discharge and meandering streambed filled with a continuous layer of leaf litter. In total 66 fungal species were distinguished whose 60% occurred in both streams. Four species - Alatospora acuminata, Clavariopsis aquatica, Flagellospora curvula and Tetrachaetum elegáns - occurred among the top-ranked species at all sites of the two streams. Key words: aquatic hyphomycetes, conidial populations, discharge, leaf litter INTRODUCTION Aquatic hyphomycetes (INGOLD 1942) are one of the groups of stream microorganisms decomposing allochthonous plant litter in woodland streams (BÄRLOCHER 1992a). To understand better their spatial and temporal distribution in different types of streams species composition and concentrations of the conidia in transport have been studied for a long time. From many studies it is obvious that water chemistry plays an important role in structuring fungal communities (BÄRLOCHER and ROSSET 1981, WOOD-EGGENSCHWILER and BÄRLOCHER 1983, MARVANOVÁ 1984, BÄRLOCHER 1987). Some other studies suggested the importance of altitude or factors associated with it (CHAUVET 1991, FABRE 1996). The effect of the composition of allochthonous litter and stream hydraulics on the occurrence and abundance of aquatic hyphomycetes in streams is less known. Spatial distribution of the aquatic hyphomycetes on eleven sites in the catchment area of the Morgó stream has recently been studied (GÖNCZÖL et al. 1999, GÖNCZÖL and RÉVAY 1999, 2003). A comprehensive statistical analysis of earlier data suggested that the effect of abiotic habitat variables and substrate composition Studia Botanica Hungarica 35, 2004 Hungarian Natural History Museum. Budapest
