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

proves that Cyanophyceae are able to live, — indeed, to form associations, — in conditions of life so extreme that they forbid the invasion of any other plant life, with the exception of certain specially thermophilous bacteria, — and they also in a very small percentage. Also the other zones, gradually retreating from the spring water, are dominated by Cyanophyceae (90—93 per cent), with the difference however, that the leading role in the association of Mastigocladus laminosus Cohn is taken over in degrees by Symploca thermalis (Kütz.) Gom., that is, by Schizothrix calcicola (Halász, 1949). B) Cooling basins. The constitution of the microvegetation in the cooling basins still show a close relation to those of the springs. The open and constantly steaming concrete basins of considerable sizes fill up by spring water unexposed to the open air. The water, issuing from the depths, arrives through closed pipes directly into the basins. In the cooling basins, the associations of the microvegetation develop and undergo certain changes in connection with, and under the influence of, the artificially regulated temperature and the large bodies of water. Consequently, Mastigocladus laminosus can be found solely in some filamentous fragments, and the unicellular Cyanophyceae attain dominancy beside the filamentous algae, especially Gloeocapsa gelatinosa Kütz., and Aphanothece bullosa (Menegh.) Rabenh. It is yet to be noted that, whilst the colonies built up of the monotonous body of some Cyanophyceae species in the basin of the highest temperature (54 °C) constitute 75 per cent of the microvegetation (beside the sulphur and ferro-bacteria of 25 per cent), Cyanophyceae are present in 90 per cent in the basins of 40 °C and 28—30 °C temperatures. This ration is, though striking, in accordance with the observed cases of occurrence concerning the blue-green algae, whose optimal temperature is about 40—45 °C. Chlorophyceae are absent as yet, the same as from the springs themselves (Vouk, 1937 ; Prát, 1954). CJ Mud basins. In the mud basins, above the oxydization and condensed steam zones over the hot mud, the pyriophytous Cyanophyceae are represented by 1—2 species solely, building monotonous colonies. Here the unicellular Chlorophyceae first appear. Their occurrence may be brought into connection with the fact that the mud permeated by the thermal water is of a cold fresh-water origin. Cyanophyceae are present in 86 per cent, as against the 13 per cent of the Chlorophyceae. DJ The swimming pools The 32°—

29°C water of the swimming pools are strongly exposed to the effects of biotical factors. Consequently, in the microvegetation flourishing here, there are present, in average values, about the same amount of Cyanophyceae (48 per cent) and Chlorophyceae (47 per cent). There are also flagellates and sulphur bacteria here. Since the Chlorophyceae are not especially thermal organisms and as their conditions of life are linked up with colder fresh waters, they generally occur, as in the hot springs of Harkány, in biotops whose temperature is not high on