To understand the factors that determine the extent of blooms of the unicellular green alga Dunaliella and halophilic Archaea in the Dead Sea, and to predict the possible effects of the planned conveyance of Red Sea water to the Dead Sea, we performed simulation experiments in the 0.9 m3 outdoor mesocosms on the grounds of the Dead Sea Works Ltd. at Sedom, as well as in the laboratory. The laboratory simulations showed that development of the Dunaliella was possible only when Dead Sea water (340 g 1-1 total dissolved salts) was diluted with minimally 10% (by volume) of Red Sea water (40 g 1-1 total dissolved salts). Addition of phosphate was essential for the algae to grow, and growth rates and yields increased with increasing phosphate concentration and decreasing salinity. Field simulations in the mesocosms showed that development of algae was rapidly followed by development of dense blooms of red halophilic Archaea, which imparted an intensely red color to the ponds. While algal numbers declined after the peak of the bloom had been reached, number of halophilic Archaea and levels of archaeal pigments remained high for over two years. Although it should be realized that the closed system formed by the shallow ponds differs from the conditions in the lake, the results suggest that a microbial bloom, once formed, can remain present in the Dead Sea for months to years. These observations are important when attempting to predict how the biological properties of the lake may change in the future, and they they have important implications for the planning of the Red Sea-Dead Sea conduit.
Oren, Aharon; Gavrieli, Jonha; Kohen, Marco; Lati, Joseph; Aharoni, Mordehay; and Gavrieli, Ittai
"Long-term mesocosm simulation of algal and archaeal blooms in the Dead Sea following dilution with Red Sea water,"
Natural Resources and Environmental Issues:
Vol. 15, Article 27.
Available at: http://digitalcommons.usu.edu/nrei/vol15/iss1/27