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

general pattern of the temporal changes of conidial concentrations recorded in most streams in temperate regions (IQBAL and WEBSTER 1973, BÄRLOCHER and ROSSET 1981, CHAMIER and DIXON 1982, SHEARER and WEBSTER 1985). Delayed appearance of the peak in conidial number may be partly due to the hydrological feature of this stream (i.e. meandering stream bed, low current velocity and constantly low discharge) inducing a certainly high, litter retentive capability. The main reason for the relatively high conidial concentration still in June may be the same. The minimum conidial concentration (748/1) in January can be attributed to the almost entirely frozen stream and the restricted water movement. The proportion of scolecoconidia in the conidial populations in the Csömöle stream was strikingly high. The analysis showed that scolecoconidia accounted for 48% (19 species) and 29.5% (21 species) of the conidia collected in the Csömöle stream and the Morgó stream, respectively. No reasonable explanation for this structure of the conidial pools could be found. Nevertheless, as one speculation comes up that low discharge combined with very low current speed in a woodland stream may be preferred by scolecosporous species. Whether hydrological feature may select species in particular stream habitats certainly requires further studies. The total number of species (45) is comparable to the species numbers detected at any, especially the two lowermost sites (Site V = 44, Site VI = 45) of the Morgó stream (GÖNCZÖL et al. 1999). The slightly alkaline character of the stream appears not to diminish the fungal species number. Considering taxonomic difficulties in the identification of conidia the actual number of species is certainly even higher. The present investigation, like some earlier studies, also confirms that softwater and hardwater streams in various geographical areas in Hungary support fungal communities with closely similar species numbers (GÖNCZÖL 1987, GÖNCZÖL and RÉVAY 1992). Two species, Flagellospora leucorhynchos and Sigmoidea praelonga, have not been found yet in the Morgó stream, but had already been reported from two hardwater streams of the Aggtelek National Park, Hungary (GÖNCZÖL and RÉVAY 1992). The identification of Flagellospora leucorhynchos is somewhat difficult since it may easily be confused with F. curvula. Whether its abundant occurrence is restricted to small streams with similar hydrological features to those of Csömöle, Patkós and Kecske-kút streams (Aggtelek Mts) require further investigations. Extremely high proportion (48.3%) of Alatospora acuminata was detected in December. A similarly high percentage (42.6%) of this species was obtained earlier in an October sample at Site II of the Morgó stream. These high values at both sites coincided with the annual peak concentration of the stream spora. Tricladium angulatum proved to be a dominant species in April, October and December. Its considerable occurrence in this stream further confirms our as-