Algae of the Sefunim Cave (Israel): species diversity affected by light, humidity and rock stresses

Algal flora was studied in the stalagmite Sefunim Cave located in Mount Carmel about 10 km south of Haifa, Israel. A total of 69 species of algae were revealed belonging to Cyanoprokaryota (45), Chlorophyta (15), Bacillariophyta (7), and Xanthophyta (2); among them, 13 species are newly recorded for Israel. Cyanoprokaryotes proved to be the most diverse and abundant group in all studied cave environments. Number of species sharply decreased from the entrance to the depth of the cave (from 46 to 26 species) manifesting prior importance of light intensity for species diversity. Taxonomic composition of the algae changed along the gradient of illumination as well: in cyanoprokaryotes the share of chroococcal species decreased and of oscillatorian species increased from the entrance to the end of the cave. As for eukaryotic algae, in the inner chamber of the cave, xanthophytes disappeared from the floristic spectrum; diatoms took the lead over Chlorophyta in species richness. In the studied environment, species and taxonomic diversity of diatoms, to a greater extent, depended on the presence of additional moisture than on the level of illumination. It was revealed that light intensity, availability of dripping, and kind of rock substratum affected the structure of cavernicolous algal communities.