Szekessy Vilmos (szerk.): A Magyar Természettudományi Múzeum évkönyve 55. (Budapest 1963)
Halász-Halmi, M.: Microphyto-sociology of the acrothermal springs at Harkány and at Budapest - Mt. Gellért
162 Survey Area I: The basin of the „Old Spring'" (Thermal Spring I.) The cast-stone basin of the „Old Spring" was built about a hundred years ago, and never rebuilt or otherwise disturbed since that time. It stands in the open air, hence the ecological conditions are rather favourable by reason of the long period of years allowing the development of an undisturbed acrothermal mierovegetation. The basin has a perpendicular wall on the one side and, opposite to it, a semicircular one, slanting gradually away from the perpendicular at the brim to the horizontal at the centre of the bottom of the semicircular basin. Its diameter is 0,8 m. The temperature of the spring water is 62 centigrades, and the rising vapours constantly fill the space inside the basin, while the lower parts of the walls are incessantly sprinkled by the hot drops of the acrothermal spring water; its hydrogen-ion concentration being 6,8. The microvegetation developed in macroscopically distinguishable zones ranging closely above each other on both walls of the basin. Semicircular Wall. On this gradually sloping wall, there are six zones above each other, but the two lowest zones were washed away by the drift of the spring water. Zone 111 has the highest surrounding temperature of all the investigated zones (42—37,5 centigrades), lying nearest to the spring water. Its algal laver is 1—1.5 mm thick. As the analysis of 60—70 „MinimiAreals" shows, the dominant species in this warmest zone of the biotop is Hapalosiphon laminosus. Its covering degree is mostly 5, sometimes 4. Accompanying this dominant species appear Symploca thermalis, Phormidium laminosum, Gloeocapsa gelatinosa. However their covering is sporadical, reaching only occasionally degree 1—2. Consequently we designate the association of the zone as Hapalosiphonetum laminosi. Zone IV. In this zone, the temperature of the surrounding atmosphere decreases 5—7 centigrades (37,5—35). as compared to that of zone III. The algal layer is 2—3 mm thick. In this somewhat cooler temperature, Hapalosiphon laminosus loses its former dominance, the covering degree being not more than 3, while Symploca thermalis appears in greater quantities than in zone III. The species becomes more frequent as we proceed towards the upper edge of the zone, and the covering degree reaches grade 4. In company of the two dominants, the species Gloeocapsa gelatinosa, Cluoococcus vari us . Phormidium orientale Synechococcus elongatus appear but sporadically, or sometimes reaching degree 1. We denote the association of this zone as Symploceto-Hapalosiphonetum laminosi. Zone V. In this zone, ranging immediately above the former one and closely connected with it, the temperature of the surrounding atmosphere decreases to 35—32 centigrades. The algal layer is 2—2,5 mm thick. According to the detailed microsociological investigations, Symploca thermalis gains here dominance, while the abundance of Hapalosiphon laminosus decreases and obtains a covering degree of only 1 or 2; sometimes it appears only sporadically. The other accompanying species are generally the same as in the former zone, and have a very low covering degree between 1 and sporadical. The association of this zone is to be named Symplocetum thermalis. Zone VI. This is the last one in the series of subsequent zones, and it occupies the outer end of the semicircular algal community in the basin. Its surrounding atmosphere has a comparatively low temperature, fluctuating between 32—27 centigrades; the atmosphere is still saturated with thermal vapours.
