Long-term mesocosm simulation of algal and archaeal blooms in the Dead Sea following dilution with Red Sea water

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

The onset of the Messinian salinity crisis in the deep Eastern Mediterranean basin

Astronomical tuning of the Messinian pre-salt succession in the Levant Basin allows for the first time the reconstruction of a detailed chronology of the Messinian salinity crisis (MSC) events in deep setting and their correlation with marginal records that supports the CIESM (2008) 3-stage model. Our main conclusions are (1) MSC events were synchronous across marginal and deep basins, (2) MSC onset in deep basins occurred at 5.97 Ma, (3) only foraminifera-barren, evaporite-free shales accumulated in deep settings between 5.97 and 5.60 Ma, (4) deep evaporites (anhydrite and halite) deposition started later, at 5.60 Ma and (5) new and published 87Sr/86Sr data indicate that during all stages, evaporites precipitated from the same water body in all the Mediterranean sub-basins. The wide synchrony of events and 87Sr/86Sr homogeneity implies inter-sub-basin connection during the whole MSC and is not compatible with large sea-level fall and desiccation of the Mediterranean

The effect of a phosphonate-based antiscalant on the morphology and precipitation kinetics of gypsum: The Red Sea – Dead Sea project

The proposed plan for the 'Red Sea – Dead Sea project' has raised concerns that the surface water of the Dead Sea would turn white due to gypsum precipitation. The occurrence of such an event would depend on the precipitation kinetics and the morphology of the precipitating crystals. Batch experiments were conducted to study the effect of a phosphonate-based antiscalant on the precipitation kinetics and morphology of gypsum under the conditions of this project. Addition of the antiscalant was found to increase the induction time by a factor of 1.2-5 over the entire range of Dead Sea – Seawater mixtures investigated, depending on brine composition. Once nucleation occurred, the antiscalant also slowed the crystal growth by a factor of 1.2-3. However, when the solutions were seeded with gypsum, the rate of crystal growth with and without antiscalant were similar, within uncertainty. More crystals precipitated from unseeded solutions with no antiscalant and the crystals were smaller and less tabular than those precipitated from unseeded solutions with antiscalant

The Expected Impact of the Peace Conduit Project (The Red Sea – Dead Sea Pipeline) on the Dead Sea

brines, Dead Sea, desalinization, gypsum precipitation, Israel, Jordan, microbial blooming, peace conduit, sustainable development, water balance, water level,

The Mg isotope signature of marine Mg-evaporites

Marine Mg-evaporites are a small oceanic sink of magnesium, precipitating only from extremely evaporated brines. The isotopic composition of Mg in seawater, δ26Mgseawater, has recently been shown to be an effective tool for reconstructing the Mg budget of the modern and past oceans. However, estimations of the Mg isotope fractionation between the Mg-evaporites and their precipitating solution are required for full quantification of the isotope effect of the evaporitic sink on δ26Mgseawater, as well as for utilizing ancient evaporitic sequences as an archive for past δ26Mgseawater. Here, we estimate the Mg isotope fractionation between Mg-evaporites and modern marine-derived brine along the course of seawater evaporation, up to degree evaporation of >200. The sequence of Mg-salts included epsomite (MgSO4·7H2O), kainite (KMgClSO4·3H2O), carnallite (KMgCl3·6H2O), kieserite (MgSO4·H2O) and bischofite (MgCl2·6H2O). The following isotope fractionation values, either negative or positive, were calculated from the isotope difference between the salt and its precipitating brine, and from the evolution of δ26Mg in the brine throughout the evaporation: Δcarnallite-brine = +1.1‰, Δepsomite-brine = +0.59‰, Δbischofite-brine = +0.33‰, Δkieserite-brine = −0.2‰ and Δkainite-brine = −1.3‰. Magnesium isotopic compositions determined on minerals from different ages in the geological record corroborate well these results. Due to precipitation of multi-mineral assemblages having isotope fractionation values of opposing signs, the δ26Mg value of the brine changes only slightly (50%). The isotope fractionations are shown to correlate with the number of water molecules coordinated to the Mg2+ and with Mg-O bond length in the mineral lattice. Given these isotope fractionations, it is calculated that a volume of 0.4 · 106–0.8 · 106 Km3 of a mono-mineral assemblage of kainite or carnallite needs to precipitate in order to change seawater δ26Mg by only 0.1‰. This huge volume is by far larger than the volume of these minerals known to date in the global geological record. Therefore, it is concluded that the impact of Mg-evaporites formation on δ26Mgseawater has been insignificant since the Proterozoic. The results of this study suggest that the Mg isotopic composition of Mg-evaporites preserved in the geological record of evaporitic basins may be used to: 1) quantify geochemical processes that fractionate Mg-isotopes within these basins, such as dolomitization; and 2) complete the secular variations curve of the marine δ26Mg record using basins with well-established evaporitic sequences.ISSN:0016-7037ISSN:1872-953

A highly active karstic aquifer bounded by saline waters: The Judea Group aquifer

The freshwater of the Judea Group aquifer that recharges on the crest of the Judea and Samria Mountain ridge flows east and west, defining two groundwater basins. At the foothills of both basins the freshwater encounters ancient saline or brackish water. The mode of interaction between the two water bodies within each basin is different, although both eventually discharge as brackish spring system. We describe these systems and identify the source of the higher salinity end members

Precise determination of dolomite content in marine sediments

Dolomite (CaMg[CO3](2)) is a common rock-forming mineral. Nevertheless, its mechanisms of formation and the factors that cause dolomite concentration variations within the sedimentary records constitute long-standing geochemical questions. In addition, the flux of Mg2+ leaving the ocean by the formation of dolomite is a controversial question, with some studies arguing that dolomite formation is a negligible Mg2+ sink in the modern ocean, while others show that it constitutes more than 50% of the total Mg2+ removal rate. An important factor that impedes the resolution of the dolomite Mg2+ flux is the lack of analytical methods with adequate precision and detection limit to directly measure minute quantities of authigenic dolomite in marine sediments. Here, we present a new analytical method for direct, precise measurement of dolomite content in marine sediments. The method is based on sequential leaching of carbonate minerals in acid and tracks the CO2 emitted by the dissolution. Based on the measurement of gravimetric standards of calcite and dolomite, the method's detection limit and precision were determined as better than 0.2 and +/- 0.2 dry wt% of dolomite, respectively. The method out-performed dolomite quantification made by x-ray diffraction and by inductive coupled plasma mass-spectrometry, which provided precision of +/- 2 and +/- 1 dry wt%, respectively. Measurements of the dolomite content in modern sediments from the seafloor below the oligotrophic Eastern Mediterranean and the eutrophic Mississippi plume, and in clayey-silty alluvial soil from south-eastern Israel, demonstrated that the aforementioned precisions are also valid for natural samples.ISSN:1541-585