Species composition and diversity of aero-terrestrial algae and cyanobacteria of the Boreč Hill ventaroles.

Abstract

The algal flora of the Boreč Hill ventaroles was examined and compared with the flora of their close surroundings. In comparison to unaffected sites, the ventaroles differ in seasonal temperature fluctuation as well as in soil pH. Winter exhalations caused by continual air circulation in the cranny system of rock massive result in a significant increase in air temperature and soil pH. The ventaroles were inhabited by a markedly richer and more diversified algal flora. Over half of investigated species occurred only in the ventaroles, including all chrysophyte, eustigmatophyte and desmid taxa. In contrast to the unaffected sites, different algal populations were discovered in the ventaroles. The investigated species could be separated into two groups: ventarole-specific ones preferentially occurred in both the ventaroles, and those occurred only in a large ventarole. There, water condensation in moss plants during winter exhalations enables a short-term occurrence of several algal species preferring aquatic environments. The diatom flora of the ventaroles resembles well the species composition found in the caves. By contrast, the desmid flora is rather similar to algal communities found in ephemeral water bodieslike temporary peat bog pools or dripping rocks. Thus, the Boreč Hill ventaroles represent a unique type of biotope, with a specific algal flora adapted to periodical periods of warm, moist air exhalations of several months' duration.