Biological Productivity in the Dead Sea Part I. Microorganisms in the Water Column

Abstract

AbstractStudies were performed to determine the distribution of microbiota in the Dead Sea during 1963 to 1965. The dominant organisms in the surface water were found to be two red halophilic bacteria, followed in abundance by a green flagellated alga, Dunaliella virdis. Cultures inoculated with Dead Sea water produced growth of the red bacteria as well as unidentified non‐pigmented halo‐tolerant bacteria, capable of growing in 25% salt solution, and bacteria that grew only in dilute salt media. The latter are mainly spore‐forming aerobes, probably introduced by rain‐wash of the soil, as well as from the Jordan River and fresh water springs. Sulfate reducing bacteria were also cultured from the water and from the sediment. Pigment studies on extracts from laboratory cultures of the red bacteria, from centrifuged suspensions of Dead Sea water and, by comparison, from a pure culture of Halobacterium salinarium, showed that the dominant pigment in all cases was the carotene α‐bacteriorubrin. The total number of organisms decreased with depth of the water column, especially below the thermocline. The interpretations given for the decrease are: lack of dissolved oxygen, decrease in incident light, and lack of dissolved phosphate. The last factor is probably due to rapid precipitation of phosphate by divalent ions.