Cyanoprokaryotes and algae of arubota'im salt cave (Mount Sedom, Dead Sea area, Israel)

In the interior of the Arubota'im cave (35°24'E, 31°05'N), hollowed out in the halite rock of Mount Sedom near the Dead Sea in Israel, there were no visible life forms on the walls or on the bottom. A detailed investigation of the Arubota'im cave during winter and summer periods revealed 13 species of photosynthesizing microorganisms; among them, 11 species were cyanoprokaryotes, and two were green algal flagellates found on the external wall near the entrance to the cave. Among these species, the record of Chlamydomonas sp. is accidental on halite rock; on the salt-rich Artari's medium it became colorless and died. However, the recorded Dunaliella terricola Massjuk is a genuine halophilous species; it is newly recorded for Israel. Inside the cave only cyanoprokaryotes from Chroococcales (6 species) and Nostocales (5 species) were found. Oscillatorian algae were completely absent in the studied samples. All revealed coccoid cyanoprokaryotes, except one, were endogloeic. After inoculation, heterocystous forms demonstrated high viability. The most frequent species in the Arubota'im cave was Nostoc linckia f. terrestris Elenk.; it was recorded both in winter and summer samples collected along the cave from the entrance to the deepest end. Extremely low species diversity of cyanoprokaryotes and algae in the Arubota'im cave (compared to other Israeli caves) is caused by multifactor stress combining low-light intensity, substrate salinity, and long-term water deficit.