Sinkholes as a source of life in the Dead Sea region

Abstract

In recent decades, the Dead Sea region has suffered greatly from anthropogenic activities that have resulted in a massive decrease of the Dead Sea water level. This decrease has allowed the penetration of fresh ground water into the underground layer, which dissolved the salt layer and created sinkholes. Presently there are over 5000 sinkholes spread across the west bank of the Dead Sea, some of which are filled with water originating from rainfall, flash floods and spring water. Although sinkholes are detrimental to road infrastructure and tourist sites, they have dramatically increased the number of aquatic habitats surrounding the Dead Sea. In a cross-sectional study of 94 sinkholes along the north-west bank of the Dead Sea, coupled with a longitudinal study of six sinkholes, we examined how the community of invertebrates in the sinkholes is affected by environmental and geographic variables and how biological succession occurs in the sinkholes. We found that sinkholes are populated mainly by aquatic insects, which have high tolerance of a variety of environmental conditions. We also found that the community of invertebrates in the sinkholes is shaped by environmental variables such as salinity, pH, dissolved oxygen concentration, water temperature and the size of the sinkhole. We further found that the geographic distance between the sinkholes increases spatial species turnover and that species turnover across time was high. Patterns of species composition were similar in all the sinkholes, with the community structure during the wet season changing from early to mid-season, and then again from mid-season to late season. Interestingly, despite the extreme conditions of the water of the sinkholes, their seasonal succession processes were similar to those of temporary water bodies along the Mediterranean coast of Israel.