Boros István (szerk.): A Magyar Természettudományi Múzeum évkönyve 6. (Budapest 1955)

Halász, M.: The characteristic occurrences of blue green algae in the hot springs of Harkány

On the median parts of the perpendicular, as also on the external bands of the oblique, walls of the spring-well, this zone changes presently into the mixed associations of Schizothrix calcicola (Ag.) Gom., and Symploca thermalis (Kütz.) Gom. ; next come pure Schizothrix calcicola associations with the unicellular Gloeocapsa and Chroococcus species, associating (in gradually higher numbers) with the filamentous algae (Halász, 1949 a). The associations here discussed are the most characteristical ones of the high temperature thermae ascending from the depths of the Central Danubian Basin, though their forms of appearance and their zonal development do not always become manifest in such clearly definable articulation. There are, e. g. mixed associations in the springs of the Gellérthegy, Budapest (Halász, 1942; Istvánffy, 1892; Palik, 1949). The associations formed at the place of ascension of the spring will, concurrently with the eventual alteration of the environmental conditions, be relieved by other communities. On the walls of the cooling basins in contact with the hot water, the association of Schizothrix calcicola (Ag.) Gom., and Microcoleus sociatus (W. et G. S. West), and those of the unicellular Gloeocapsa gelatinosa Kütz. and Aphanothece bullosa (Menegh.) Rabenh. develop. In the condense steam and oxydization zones of the mud basins, the unicellular green algae also appear, besides the monotonous colonies of the Cyanophyceae. The changes in the associations of the Cyanophyceae in strict connection with the changes of temperature can be well observed in the development of the associations forming in the overflows which drains off the hot water. In contrast to the relatively constant environmental conditions of the springs and cooling basins, both the swimming pools and the whole course of the channel receiving the water of the drains of the basins are exposed to the polluting effects of biotical factors ; aggravated also, in the case of the latter, by the afflux of cold waters of allochtonous origin too. Consequently, the original and characteristical associations gradually disappear, to give up their places to newer associations adapted to the altered environmental conditions, retaining finally but fragments of the characteristical elements of the original associations. In the hot water of the overflows, the several Oscillatoria and Phormidium associations turn up, simultaneously with the decrease of temperature. Stenothermal forms gradually disappear from these associations, surrendering to eurythermal, indeed, locally to also non-thermal, elements (Cf. Table 2). II. The Distribution of the Microvegetation A) Springs. In the successive zones of the spring-wells only Cyanophyceae appear, and the presence of a Flagellate species can be shown in traces only (Halász, 1953). In the immediate vicinity of the ascending 62,6 °C hot spring water, no micro-phytoassociations occur ; most probably because the strong current of the downpouring water impedes any colonization. In the innermost association zone of 46—42 °C, nearest to the downpouring water, 93 per cent of the forming microvegetation is made of Cyanophyceae. It is worthy of note that no Cyanophyceae appear in the region of the spring wells. Besides Cyanophyceae, there are only sulphur and ferro-bacteria to be found here, and these only make up 6,5 per cent of the whole vegetation. This circumstance emphatically