Kaszab Zoltán (szerk.): A Magyar Természettudományi Múzeum évkönyve 63. (Budapest 1971)

Gönczöl, J.: Aquatic Hyphomycetes from the Mts. Börzsöny

ANNALES HISTORICO-NATURALES MUSEI NATIONAL1S HUNGARICI Tomus 63. PARS BOTANICA 1971. Aquatic Hyphomycetes from the Mts. Börzsöny By J. GÖNCZÖL, Budapest The aquatic Hyphomycetes are microscopic fungi living on decaying leaves submerged in water. From both a systematical and an ecological standpoint, their group is very interesting and considerably problematic. They liberate spores of characteristic shape—preponderantly four-branched from a common centre ("tetraradiate spore", INGOLD, 1966)—into the water. Even within this basic shape, they excel by their richness of form and variability. Besides the most frequent, tetraradiate form also other interesting spore forms are encountered: from the spirals of the Anguillosporas to the bizarre shapes of the Ingoldias. These various forms, especially the 4-branched ones, presumably facilitate floating in and dispersal by water, apparently ranging over the whole world, yet, rather unknown in detail. Subsequently to INGOLD'S basic work, published in 1942, new aquatic Hyphomycetes have been and are today described from many points of the world. Apart from BÁNHEGYI'

s comprehensive paper (1962), it were algologists who recorded the occurrence of Tetracladium marc hal ianum and T. setigerum on some occasions in Hungary (KOL, 1957; SZEMES, 1960). HORTOBÁGYI (1949) observed the mass winter occurrence of Tetracladium marchalianum in the Lake Balaton. The majority of aquatic Hyphomycetes are to be found in the clear water of mountain streams, but their role played in the life of the waters and dependence on the other members of the micro-world of natural waters (e.g. concerning algae: MARVANOVA & MARVAN, 1963), and the effects of water quality or purity on their presence are still hardly known. Investigations in this direction have hardly been made yet. SUZUKI & NIMURA (1960) studied the dependence of the aquatic Hyphomycetes on pH in Japanese lakes; DUDKA (1964) investigated some other factors of the aquatic environment, e.g. suspended oxygen. WOELKERLING & BAXTER (1968) studied the combined effects of several factors (carbon dioxyde, hardness, -nitrites, -nitrates, dissolved oxygen, pH). Comparatively more data are known on the seasonal occurrence of diverse species, though merely on the basis of occasional sampling and collecting. In the present paper, I propose to submit some data concerning the distribution and seasonal frequency of aquatic Hyphomycetes on the basis of a systematic investigation (for a whole year) of one of the brooks in the Mts. Börzsöny. Material and method (Fig. 1 and 2) I studied the conidia of aquatic Hyphomycetes deriving from the material collected in the Morgó brook of the Mts. Börzsöny, from December 1969 till December, 1970. I took my samples monthly, habitually 1.5—2 km. above the village Kismaros (Sample site I), and, for comparison, on two occasions also at a higher reach of the stream (Sample site II). The samples were taken from the accumulated foam-scum in several places of the brook, these sites being the points of natural enrichment of the water by the conidia of aquatic Hyphomycetes (INGOLD, 1966; NILSSON, 1964). The mechanism of foam formation enables namely the adherence of the swirling conidia to the aquatic membrane of the bubbles and thus their accumulation by the surfacing bubbles in the gathering froth. There is of course no guarantee that the foam thus produced yields a complete picture of the aquatic Hyphomycetes of a brook, that is, that the conidia of all species living in the water occur in the foam and that the proportions of the conidia present in it correspond to the true rates of the species. Hence the results of my studies approach only by a certain amount