Comparative analysis of algal communities in the rivers of northern and southern Israel as bearing on ecological consequences of climate change

Climatic impact on algal communities is analyzed by comparing two unpolluted river ecosystems, the Oren River of Mediterranean zone, Northern Israel and Zin River of the Central Negev Desert, Southern Israel. Bio-indication method was used for assessment of ecologically significant variations in the composition of algal communities in both rivers. Our analysis highlighted the distinctions in taxonomic diversity and abundances of both salinity tolerant (halobic) and alkaliphilic groups of algae. The ratios of high halobity to low halobity species are appreciably lower in the Oren River than in the Zin River. Although geological substrates are carbonates in both cases, the indicators of alkalic water are more prominent in the Zin River than in the Oren River, in which pH is buffered by organic substances from vegetation and soil. As a result of CCA analysis, we recognized two types of ecological communities, the alkaliphilic (high pH tolerant) and halophilic (high TDS tolerant) types. Predictably, the halophilic communities will be favored with further climate warming. The effects of climate change and anthropogenic pollution are synergistic in the case of the pollution-sensitive Chara community falling under high risk of extinction under the ongoing climate change. Crown