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Abstract

The Dead Sea is an extreme environment characterized by its high salinity ( 347 g l-1) and high concentration of divalent cations (5 M Mg2+ and 0.5 M Ca2+), where low abundance and low diversity of microorganisms are found. A newly discovered system of submarine freshwater springs along the shores of the lake presents a di erent picture, where dense microbial communities can be observed. The goal of this study was to shed light on the mystery of the spring oases in the Dead Sea. We used ultrahigh resolution mass spectrometry via the Fourier transform ion cyclotron resonance mass spectrometry technique (FT-ICR-MS), to molecularly characterized Dissolved Organic Matter (DOM) from aquifers that feed the springs, the springs and the Dead Sea . We were able to assign over 8,000 molecular formulae of individual molecules detected. Dissolved Organic Carbon (DOC) concentrations were found to be higher in the Dead Sea (1200 - 2180 uM) than in the springs (220 - 1720 uM) and aquifers(10 - 730 uM). Despite the DOC concentrations, the springs DOM is more diverse. Our results suggest that the DOM in the springs supplies the microbes with more possibilities regarding organic substrates. Molecularly, the three sets of samples di er signi cantly, however 45 % of the compounds are shared between aquifers, springs and Dead Sea, suggesting that almost half of the DOM is refractory. Additionally we suspect that the absence of polyophenols in the Dead Sea might be due the presence of aromatic degrading bacteria in the springs sediment. This study provides a rst insight into the geo- metabolome of the Dead Sea and its fresh water springs.