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The ecological state of inland waterbodies, including hyperhaline lakes, is determined by the combined influence of natural and anthropogenic factors. For the purpose of holding interannual and seasonal monitoring of the hypersaline lake Adzhi-Baichi, located on the western coast of the Crimean peninsula in the arid climate zone, we studied the change in air and water temperatures, as well as the hydrochemical parameters of brine and the dynamics of the Artemia population Artemia salina in 2017–2020. The established general trends are expressed in an increase in air and water temperature in the summer period with maximum values in July–September (above +30°С), which was accompanied by an increase in reservoir salinity and a decrease in the oxygen content. Fluctuations in the pH and values of the redox potential Eh were less pronounced. The maximum brine salinity (more than 350‰) was noted in 2017, the minimum oxygen content (0.7–1.0 mg/L) occurred in 2020, and the lowest Eh values (–78.5 mV) were found in 2019. Crustacean cysts were found in all of the studied periods during the year. Nauplii appeared in March–April at a water temperature of +3…+7°C; adults were found in the summer months and at the beginning of autumn. In summer, at high water temperature and salinity but a low oxygen content, a crustacean die-off occurred. The results reflect the characteristics of the influence of climatic and anthropogenic factors on the ecosystem of the hypersaline lake and can serve as a model for the prediction of possible scenarios of the impact of climate change on inland waterbodies and can be useful for an understanding of the processes of transformation of aquatic ecosystems in arid zones located in a region of intense anthropogenic influence, as well as the development of measures for their protection and the rational use of resources.

Inland athalassohaline solar salterns provide unique opportunity to study microbial successions along salinity gradients that resemble transition in natural hypersaline lakes. We analyzed for the first time 16S rRNA gene amplicon sequences of bacteria (V1–V2) and archaea (V4–V5) in saltern brines of India’s largest inland hypersaline Sambhar Lake. Brines of the salterns (S1–S4) are alkaline (pH 9.5–10.5) with salinities of 130, 170, 280 and 350 gL−1 respectively. 16S rRNA gene copy-number of archaea outnumbered that of bacteria in all salterns. Their diversity also increased along S1 through S4, while that of bacteria decreased. Brines of S3 and S4 were dominated by specialized extreme halophilic bacterial (Halanaerobiales, Rhodothermaceae) and archaeal (Halobacteriales, Haloferacales) members with recognized salt-in strategy for osmoadaptation. Microbial assemblages positively correlated to saltern pH, total salinity, and ionic composition. Archaea in S1 and S2 were unprecedentedly represented by poorly known as-yet uncultivated groups, Woesearchaeota (90.35–93.51%) and Nanohaloarchaeota that belong to the newly proposed nano-sized superphylum DPANN. In fact, these taxa were identified in archaeal datasets of other athalassohaline salterns after re-analysis using latest RDP database. Thus, microbial compositions in hypersaline lakes are complex and need revisit particularly for their archaeal diversity to understand their hitherto unknown ecological function in extreme environments.

In order to identify the influence of hydrometeorological conditions on the seasonal changes in the ecological state of the salt Lake Saki (Crimea), the dynamics of hydrochemical parameters of wa-ter (salinity, oxygen content, temperature, pH, Eh) and changes in the population of the brine shrimp Artemia salina L., as well as the proportion of hatching nauplii from cysts were studied in 2017 and 2018. A decrease in oxygen content and an increase in brine salinity in the summer were accompanied by an increase in air temperature and water temperature; the interannual differ-ences of these parameters were preconditioned by the hydrome-teorological peculiarities. Artemia cysts were found in the water column throughout the year; the nauplii appeared in February – March; the maximum abundance of all life stages of brine shrimp was noted in May. The proportion of hatching nauplii from cysts collected in the cold season was significantly higher than that in the warm season. The observed patterns are discussed as a pos-sible source for analyzing the transformation of hyperhaline eco-systems within the ongoing climate change and for developing the guidelines for the optimal commercial use of the mineral and biological resources of such ecosystems.

The studies of seasonal variations of some hydrochemical water characteristics (salinity, oxygen content, temperature, pH, and Eh) and the state of brine shrimp population in the typical hypersaline Lake Oiburg (Shtormovoe Vil., Crimea) have clearly shown their dependence on weather conditions. Variations have been established in the population size of brine shrimp, their life stages in the lake, as well as the extent of nauplii emergence from crustacean cysts (from 0.5% in March to 11.0% in February). Because of the ancient origin of Crimean hypersaline lakes (they number 45), which have formed 6500–7000 years ago, the processes taking place in them can be used to reconstruct the climatic and evolution events on the Earth in the distant geological epochs. The potential use of the annual dynamics of climatic, hydrochemical, and environmental characteristics of a salt lake in the model is discussed in the context of studying the effects of climate warming, the ensuing trends in the abiotic conditions in the water body, and their effect on biota.

Cultivation and molecular approaches were used to study methanogenesis in saline aquatic system of the Lake Elton (southern Russia), the largest hypersaline lake in Europe. The potential rates of hydrogenotrophic, acetoclastic, methylotrophic and methyl-reducing methanogenesis and diversity of the growth-enriched for by adding electron donors methanogenic communities were studied in the sediment slurry incubations at salinity range from 7 to 275 g/L. The most active pathway detected at all salinities was methylotrophic with a dominance of Methanohalobium and Methanohalophilus genera, at salt saturation and moderately halophilic Methanolobus and Methanococcoides at lower salinity. The absence of methane production from acetate, formate and H2/CO2 under hypersaline conditions was most probably associated with the energy constraints. The contribution of hydrogenotrophic, acetoclastic, and methyl-reducing methanogens to the community increases with a decrease in salinity. Temperature might play an important regulatory function in hypersaline habitats; i.e. methylotrophic methanogens and hydrogenotrophic sulfate-reducing bacteria (SRB) outcompeting methyl-reducing methanogens under mesophilic conditions, and vice versa under thermophilic conditions. An active methane production together with negligible methane oxidation makes hypersaline environments a potential source of methane emission.

Microbialites are microbial communities that create a carbonate structure. They are abundant in the Great Salt Lake, a hypersaline lake in the arid Great Basin of the USA, where they contribute to overall primary production, seasonally up to 55%. While the microbial diversity of microbialites has been investigated, how abiotic factors affect the abundance of their primary constituents is not well understood. We examined how microbialite primary producers respond to varying levels of temperature, salinity, and nitrogen within ranges observed in the Great Salt Lake. All abiotic factors and their interactions significantly affected the maximum chlorophyll-a abundance, suggesting that these factors co-limit microbialite primary producers in the Great Salt Lake. Maximum chlorophyll-a concentrations increased with nitrogen additions and showed a parabolic relationship with salinity and temperature with peaks around 60 ppt and 20°C, respectively. While salinity had a strong effect on microbialite primary producers, we found that temperature and nitrogen were more impactful, accounting for 40 and 30% of the variance in maximum abundance, respectively, while salinity contributed just 15%. Our results show the importance of the interplay of abiotic factors on Great Salt Lake microbialites and highlight the need for increased study of benthic communities in inland saline lakes.

Hypersaline waters with a salinity exceeding 35 g/L are widely distributed on the planet (hypersaline lakes and lagoons, deep-water “lakes,” and pore waters of sea ice) and are among the most extreme habitats on Earth. The present work analyzes and summarizes the results of long-term research on hypersaline lake and lagoon ecosystems in the Crimea, along with the literature data. The analysis shows that these extreme ecosystems are unique in terms of the physical and chemical parameters and processes, as well as the structure and functioning of the biota inhabiting them. In particular, salinity affects the freezing and boiling points of water. Thus, water remains liquid in a hypersaline environment, and life can exist in a wider temperature range than in fresh and sea waters, e.g., from –35 to 109°С at a salinity of 350 g/L. With a salinity increase, the species diversity sharply declines in eukaryotic organisms and grows in prokaryotes. The energy supply to ecosystems in freshwater and marine ecosystems is primarily ensured by oxygenic photosynthesis, while that in hypersaline waters comes from three phototrophic and a variety of chemosynthetic mechanisms. Thus, for example, anoxygenic photosynthesis may result in 50% or more energy (up to 85%) in an ecosystem, and its share in the total primary production increases with increases in salinity higher than 100–160 g/L. Despite the extreme nature of the environment, the majority of hypersaline waterbodies are highly productive. This paradox can be explained by two factors: the commonly high concentrations of nutrients in hypersaline waters and the high, small-scale, spatiotemporal variability of abiotic factors in such waterbodies, which allows for the interaction of oppositely directed processes to close nutrient cycles within one community. In response to high salinity and its sharp fluctuations, the osmoregulation mechanisms of primary producers include release into the environment of exopolysaccharides, the amount of which increases with salinity and can account for 50–70% of the primary production. This leads to an increased role of heterotrophic osmotrophs in food webs. Further insight into hypersaline ecosystem may expand our understanding of the organization of life in an extreme environment.

18 pages, 5 figures, 2 tables, supplementary material https://www.frontiersin.org/articles/10.3389/fmicb.2021.701414/full#supplementary-material.-- Data Availability Statement: All DNA sequence FASTQ files are deposited in the NCBI Nucleotide Archive under SRR14023866 (CB2 Bacterial and Archaeal), SRR 14023937 (GSL 3510 Bacterial and Archaeal), SRR14023877 (GB14 Bacterial and Archaeal), SRR14023878 (CB2 Viral), SRR14023865 (GSL3510 Viral), and SRR14023938 (GB14 Viral). The Bioproject id is PRJNA714934. The NCBI genome accession numbers for the MAGs and viral assemblies are shown in Supplementary Table S10, Viruses play vital biogeochemical and ecological roles by (a) expressing auxiliary metabolic genes during infection, (b) enhancing the lateral transfer of host genes, and (c) inducing host mortality. Even in harsh and extreme environments, viruses are major players in carbon and nutrient recycling from organic matter. However, there is much that we do not yet understand about viruses and the processes mediated by them in the extreme environments such as hypersaline habitats. The Great Salt Lake (GSL) in Utah, United States is a hypersaline ecosystem where the biogeochemical role of viruses is poorly understood. This study elucidates the diversity of viruses and describes virus–host interactions in GSL sediments along a salinity gradient. The GSL sediment virosphere consisted of Haloviruses (32.07 ± 19.33%) and members of families Siphoviridae (39.12 ± 19.8%), Myoviridae (13.7 ± 6.6%), and Podoviridae (5.43 ± 0.64%). Our results demonstrate that salinity alongside the concentration of organic carbon and inorganic nutrients (nitrogen and phosphorus) governs the viral, bacteria, and archaeal diversity in this habitat. Computational host predictions for the GSL viruses revealed a wide host range with a dominance of viruses that infect Proteobacteria, Actinobacteria, and Firmicutes. Identification of auxiliary metabolic genes for photosynthesis (psbA), carbon fixation (rbcL, cbbL), formaldehyde assimilation (SHMT), and nitric oxide reduction (NorQ) shed light on the roles played by GSL viruses in biogeochemical cycles of global relevance, The funding for this project was provided by the United States National Science Foundation with project number 1510255, With the institutional support of the ‘Severo OchoaCentre of Excellence’ accreditation (CEX2019-000928-S)

The study presents the results of long-term (2006-2014) research on the non-biting midges (Diptera, Chironomidae) in macrozoobenthic communities of five saline rivers (the Khara, the Lantsug, the Bolshaya Samoroda, the Chernavka, and the Solyanka) flow into hypersaline Lake Elton (Volgograd Province). The rivers have a high mineralization gradient from 4 to 41.4 g/L and diff er in size as well as in the spatial dynamics of hydrological-hydrochemical and hydrophysical parameters. In the mouth reaches, water mineralization in these rivers may exceed 100 g/L. In total, 25 chironomid taxa have been identified, 10 of which were typical of the Solyanka River and Chernavka River where salinity was above 20 g/L. In diff erent years, Chironomus aprilinus Meigen 1838, Ch. salinarius Kieff er, 1915, and Cricotopus salinophilus Zinchenko, Makarchenko et Makarchenko, 2009 were dominant in the Solyanka and Chernavka rivers and so was Tanytarsus kharaensis Zorina et Zinchenko, 2009 in the Khara and Bolshaya Samoroda. The chironomids of the benthic communities of saline rivers are represented by eurybiontic halo-tolerant species. Their distribution and abundance are linked to a complex of hydrological-hydrochemical factors, e.g., the level of overgrowth, water temperature, pH, soil particle size, etc. The chironomid diversity is strongly correlated with mineralization, although there is no clear relationship between chironomid abundance or biomass and mineralization between 6 and 41.4 g/L. The seasonal dynamics of abundance and biomass of chironomid larvae is characterized by spatial heterogeneity due to features of the life cycles of the most numerous multivoltine chironomids.

Lake Urmia, located in northwestern Iran, a hypersaline lake, divided into north and south basins by a causeway. The lake has been facing a serious environmental crisis, due to water misman...

Microbiological activity can exert a substantial influence on carbonate mineral precipitation, but linking specific microbiological processes to carbonate minerals in an environmental setting is complex, as both abiotic and biotic factors ultimately influence carbonate mineral precipitation. The coral atoll of Kiritimati, Republic of Kiribati (1.9°N, 157.4°W), in the central tropical Pacific Ocean, contains hundreds of shallow water brackish to hypersaline lakes that contain a range of carbonate and evaporite minerals. Previous studies of Kiritimati lakes have investigated the microbial communities of finely laminated microbial mats and associated microbialites found in several of the more hypersaline lakes on the island. However, the microbial communities of the more brackish lakes are unknown. These brackish lakes precipitate metres of fine‐grained carbonate muds, which are useful for palaeoenvironmental reconstruction. Here, the relationships between carbonate abundance, mineralogy, water chemistry, and bacterial and archaeal communities are investigated in a suite of brackish to hypersaline lakes (8.7‐190 ppt) on Kiritimati. Next generation 16S rRNA gene sequencing of bacteria and archaea indicate that brackish lake sediments contain distinct microbial communities. In relation to carbonate precipitation, the relative abundance of Cyanobacteria, Choloroflexi and Deltaproteobacteria is greater in the brackish lake sediments, suggesting photosynthesis and sulphate reduction associated with these taxa may strongly influence alkalinity and carbonate precipitation in brackish lakes. The presence of dolomite in certain hypersaline lakes also coincided with the presence of a methanogenic family, indicating that methogenesis may contribute to dolomite precipitation in these lakes.

This is the comparative investigation of the composition of phototrophic microbial mats developing in sulfide-rich saline Chokrak springs with outflow at the shore of the hypersaline lake Chokrak by means of next-generation sequencing. The springs are characterized by low temperature (~ 15 °C), near-neutral pH (6.7-8.5), and high-sulfide content. In the species composition the benthic microbial communities of Chokrak springs are similar to microbial mats of marine supralittoral and lagoons. Our results showed that salinity limitation had a significant effect on the species composition of benthic microbial communities developing at the outflow of the Chokrak springs. Predominant oxygenic phototrophs belonged to the genera Phormidium, Lyngbya, Leptolyngbya, Geitlerinema, and Arthrospira. Anoxygenic phototrophic bacteria were represented by halophilic green sulfur bacteria Prosthecochloris spp., halotolerant Chlorobaculum sp., as well as marine and extremely halophilic purple bacteria Roseospira, Rhodovibrio, and Halochromatium. Monoculture of a new species of halotolerant anoxygenic filamentous phototrophic bacteria was isolated.

Background and Objectives: Halothermophilic bacteria are adapted to high osmolarity and can grow in high saline environments and high temperatures. This study was aimed at the isolation of halothermophilic bacteria from Howz-e Sultan hypersaline lake in the central desert zone in Iran. Materials and Methods: Samples were collected and after preparing dilutions, the samples were cultured on Molten haloid agar with differentsalt concentrations (5-35%), then the plates were incubated at 35-70ºC in both aerobic and anaerobic conditions. Biochemical characterizations, utilization of carbon sources, production of exoenzymes and antibiotic susceptibility were investigated. Taxonomic and phylogenetic analyses were performed using 16S rRNA gene sequences. Results: One of the isolated bacteria was found to be Gram-positive, hyperhalophilic, thermophilic, endospore-forming, and was named as 1-9 h isolate. The bacterial cells were bacilli-shaped, which produced endospores at a subterminal position. This isolate was an aerobe and facultative anaerobe and grew between pH 5.0 and 10.0 (optimal growth at pH 7.0-7.5), at temperature between 15°C and 65°C (optimal growth at 40-45°C) and at salinity of 9-32% (w/v) NaCl, growing optimally at 18% (w/v) NaCl. On the basis of 16S rRNA gene sequence analysis, isolate 1-9 h belongs to the genus Bacillus within the phylum Firmicutes and showed the closest phylogenetic similarity to Gracilibacillus sp. IBP-V003 (99.0%). Conclusion: Based on the results of its phenotypic and genotypic properties, strain 1-9 h represents a novel strain of the genus Gracilibacillus. It can be used in various fields of industry and biotechnology.

Lake Magic is an extremely acidic, hypersaline lake found in Western Australia, with the highest concentrations of aluminum and silica in the world. Previous studies of Lake Magic diversity have revealed that the lake hosts acid- and halotolerant bacterial and fungal species. However, they have not canvassed microbial population dynamics across flooding, evapo-concentration and desiccation stages. In this study, we used amplicon sequencing and potential function prediction on sediment and salt mat samples. We observed that the bacterial and fungal diversity in Lake Magic is strongly driven by carbon, temperature, pH and salt concentrations at the different stages of the lake. We also saw that the fungal diversity decreased as the environmental conditions became more extreme. However, prokaryotic diversity was very dynamic and bacteria dominated archaeal species, both in abundance and diversity, perhaps because bacteria better tolerate the extreme variation in conditions. Bacterial species diversity was the highest during early flooding stage and decreased during more stressful conditions. We observed an increase in acid tolerant and halotolerant species in the sediment, involved in functions such as sulfur and iron metabolism, i.e., species involved in buffering the external environment. Thus, due to activity within the microbial community, the environmental conditions in the sediment do not change to the same degree as conditions in the salt mat, resulting in the sediment becoming a safe haven for microbes, which are able to thrive during the extreme conditions of the evapo-concentration and desiccation stages.

Lake littoral zones can also be regarded as another extremely hypersaline environment due to hypersaline properties of salt lakes. In this study, high-throughput sequencing technique was used to analyze bacteria and fungi from different rhizocompartments (rhizosphere and endosphere) of four dominant plants along the salinity gradient in the littoral zones of Ejinur Salt Lake. The study found that microbial α-diversity did not increase with the decrease of salinity, indicating that salinity was not the main factor on the effect of microbial diversity. Distance-based redundancy analysis and regression analysis were used to further reveal the relationship between microorganisms from different rhizocompartments and plant species and soil physicochemical properties. Bacteria and fungi in the rhizosphere and endosphere were the most significantly affected by SO42–, SOC, HCO3–, and SOC, respectively. Correlation network analysis revealed the potential role of microorganisms in different root compartments on the regulation of salt stress through synergistic and antagonistic interactions. LEfSe analysis further indicated that dominant microbial taxa in different rhizocompartments had a positive response to plants, such as Marinobacter, Palleronia, Arthrobacter, and Penicillium. This study was of great significance and practical value for understanding salt environments around salt lakes to excavate the potential microbial resources.

Study Region Lake Urmia, Iran. Study focus There is widespread interest in restoring drying saline lakes. At Iran’s hypersaline Lake Urmia, managers have sought a uniform target lake level of 1274.1 m above sea level to lower salinity below 263 g L−1 and recover Artemia to sufficient densities to support flamingos. We suggest that addressing a broader range of objectives will allow more flexibility for managing the lake. We define eight restoration objectives to lower salinity, sustain Artemia and flamingo populations, separate islands from each other and the mainland, reduce lakebed dust, maintain commercially valuable ions, and improve recreational access from resort beaches. We use 40 years of experimental, field, satellite, and model data to relate each objective to lake level. We describe variations through time and associated uncertainties for meeting each objective. New hydrological insights We show that:1) Lake variations prevent setting a precise target restoration level; 2) The current target may not sufficiently lower salinity to recover Artemia to sufficient densities to support flamingos; 3) Restoration objectives do not converge to a single lake level; tradeoffs are murky; 4) Lake Urmia managers should focus on multiple ecosystem services and track how they are met as lake level varies over time; and 5) As information about the lake improves, managers should adapt their management strategies to meet the most attainable objectives.

Increased salinisation of surface waters poses growing threats to agro- and aquatic ecosystems around the world. One extreme example is Lake Urmia, in northwestern Iran, which is one of the largest hypersaline lakes. Due to anthropogenic and climate-induced changes, the salinity of Lake Urmia has reached a maximum level of 420 PSU in recent years. This high salinity has endangered the food web and biodiversity in the regional ecosystem and caused an ecological regime shift. However, salinisation processes in the lake have not been well-explored yet. To address this, a combination of in-situ and remote sensing observations along with a numerical hydrodynamic model was used to study the salinity dynamics of the lake. To simulate the water salinity distribution, a three-dimensional hydrodynamic model of the lake was developed based on Finite Volume Community Ocean Model (FVCOM) and validated using field data. Wind field, heat flux, precipitation, and surface water evaporation were constructed based on meteorological data. The PHREEQC inverse modeling was then applied to obtain the precipitation and dissolution rates of minerals species. Simulated results indicate that the sedimentation and dissolution of minerals have a significant effect on the salinity levels of the lake. Although brine discharges of rivers to the lake increase the salinity of the lake, the elevated salinity of the lake is dominantly caused by the salt precipitation/dissolution processes. The results of this study provide a better understanding of the impact of precipitation and dissolution mechanisms on salinity dynamics in saltwater bodies.

The aim of this study is to establish the potential effect of changes in climate and anthropic interventions made over time on the hydro-chemical properties of the Techirghiol Lake. Located in the littoral region of the Black Sea, Techirghiol Lake is the most hypersaline lake of Romania&mdash, well-known for the therapeutic properties of the saline water and sapropelic mud. Long-term time series of salinity and water level were investigated in relation to the lake water inputs (precipitation, overland flow and groundwater), to chemical parameters (pH, DO and BOD5) and also to the hydraulic works designed and built in the region. The obtained results reveal a degradation of this ecosystem in the period of 1970&ndash, 1998, when the extensive irrigation practice in the proximity of the lake had a negative effect on the water budget of Techirghiol Lake (an increased freshwater input through runoff and seepage), followed by a major decrease of the lake&rsquo, s salinity.

International audience; Chott El Jerid is the largest hypersaline ephemeral lake in southern Tunisian Sahara desert and is one of the biggest depressions at the North of Africa. This study aimed to investigate the diversity and abundance of microbial communities inhabiting Chott El Jerid during wet season (when it was flooded), using molecular methods [Illumina Miseq sequencing, DGGE and qPCR (qPCR)]. 16S rRNA gene analyses revealed that bacterial community was dominated by Proteobacteria (especially Ralstonia species), followed by Firmicutes, Bacteroidetes, Cyanobacteria, Actinobacteria and Verrucomicrobia. The results obtained using prokaryotic universal primers showed low relative abundance of Archaea dominated by few OTUs related to Methanosarcinaceae and Methanomassiliicoccaceae families and the presence of sulfate-reducing Archaea affiliated with Archaeoglobus. However, the results obtained using Archaea-specific primers showed that archaeal community was mainly composed of aerobic Halobacteria (especially Halorubrum species) and anaerobic members of Methanomicrobia. These results also provided evidence for the presence of members of the genus Halohasta in this environment. qPCR results revealed that Archaea were more abundant in studied samples than Bacteria. The sulfate-reducing Bacteria were also found abundant (~ one-third of the bacterial community) and outnumbered methanogens, suggesting their potential important role in this sulfate-rich and hypersaline ecosystem.

Lake Hayward is one of only about 30 hypersaline lakes worldwide that is meromictic and heliothermal and as such behaves as a natural salt gradient solar pond. Lake Hayward acts as a local groundwater sink, resulting in seasonally variable hypersaline lake water with total dissolved solids (TDS) in the upper layer (mixolimnion) ranging between 56 kg m −3 and 207 kg m −3 and the deeper layer (monimolimnion) from 153 kg m −3 to 211 kg m −3 . This is up to six times the salinity of seawater and thus has the highest salinity of all eleven lakes in the Yalgorup National Park lake system. A program of continuously recorded water temperature profiles has shown that salinity stratification initiated by direct rainfall onto the lake’s surface and local runoff into the lake results in the onset of heliothermal conditions within hours of rainfall onset. The lake alternates between being fully mixed and becoming thermally and chemically stratified several times during the annual cycle, with the longest extended periods of heliothermal behaviour lasting 23 and 22 weeks in the winters of 1992 and 1993 respectively. The objective was to quantify the heat budgets of the cyclical heliothermal behaviour of Lake Hayward. During the period of temperature profile logging, the maximum recorded temperature of the monimolimnion was 42.6 °C at which time the temperature of the mixolimnion was 29.4 °C. The heat budget of two closed heliothermal cycles initiated by two rainfall events of 50 mm and 52 mm in 1993 were analysed. The cycles prevailed for 11 and 20 days respectively and the heat budget showed net heat accumulations of 34.2 MJ m −3 and 15.4 MJ m −3 , respectively. The corresponding efficiencies of lake heat gain to incident solar energy were 0.17 and 0.18 respectively. Typically, artificial salinity gradient solar ponds (SGSP) have a solar radiation capture efficiencies ranging from 0.10 up to 0.30. Results from Lake Hayward have implications for comparative biogeochemistry and its characteristics should aid in identification of other hitherto unknown heliothermal lakes.

Fluctuations in salinity are known to influence coastal marine communities. In this study, we present the effect of salinity on the distribution characteristics of mesozooplankton in Pulicat lake, the second largest lagoon situated along the south east coast of India. During different seasons of the study period, salinity varied from hyposaline (12.57) to hypersaline (139.74) in the lake. Salinity values were moderate in southern (33.75 ± 0.7) and northern inlets (29.38 ± 4.33), which were connected with the sea; while in the central region of the lake salinity was observed to be higher (52.32 ± 4.57). Mesozooplankton biovolume and abundance were high in the southern and northern inlets whereas a severe reduction in diversity and abundance was observed in the central region of the lake manifesting that increase in salinity is negatively impacting the mesozooplankton distribution. Copepod (Acartia tonsa, Acrocalanus gibber, Paracalanus parvus, Oithona brevicornis and Oithona similis), crustacean and molluscan larvae dominated the mesozooplankton abundance. A. tonsa predominance (79%) over the lake and across different seasons indicates its tolerance to a wide range of salinity fluctuations i.e., brackish to hypersaline environment of the Pulicat. The distribution of euryhaline species A. tonsa in all the sampling locations throughout the study period indicated their prevalence in the lake. Multilinear analysis between biotic and abiotic components through redundancy analysis (RDA) also suggested that salinity is the major constraint factor for the distribution of mesozooplankton. In conclusion, this study showed that the increased salinity levels have profound effects on mesozooplankton community and distribution.

The microphytobenthos is one of the key elements in the marine hypersaline water bodies. To find the general regularities of microphytobenthos distribution patterns in marine hypersaline lakes and lagoons, the accumulation of data on various cases is needed. Studies on species composition and abundance of microphytobenthos were conducted in a Crimean closed hypersaline lagoon at three stations from April to September 2018. Floating mats of the filamentous green algae Cladophora and the benthic community were investigated. Salinity varied from 23 to 170 g L−1. In total, 25 microalgal species were recorded in the mats and on the bottom, including Bacillariophyta – 19 species, Haptophyta – 2 species, Miozoa – 2 species, and Cyanobacteria – 2 species. 17 Bacillariophyta species were recorded in the mats, and 5 species at the bottom. In the mats, Bacillariophyta species contributed from 50 to 100% of the total species richness. The total microalgal abundance in the mats varied from 2.5 × 106 cells m−2 to 3.8 × 108 cells m−2 (on Cladophora filament area). In 43% of all bottom samples, there was no microphytobenthos at all or there were only single cells, due to hypoxic or even anoxic conditions under the floating mats. The average microalgal abundance in the soft-bottom community was very low, on average 4.1 × 108 cells m−2 of the bottom area. Data on fluctuations of the total microalgae abundance in mats showed that temporal variability is higher than spatial. The factor of chance is important in the determination of microphytobenthos structure variability.

Keke Salt Lake is located in the Qaidamu Basin of China. It is a unique magnesium sulfate-subtype hypersaline lake that exhibits a halite domain ecosystem, yet its microbial diversity has remained unstudied. Here, the microbial community structure and diversity was investigated via high-throughput sequencing of the V3–V5 regions of 16S rRNA genes. A high diversity of operational taxonomic units was detected for Bacteria and Archaea (734 and 747, respectively), comprising 21 phyla, 43 classes, and 201 genera of Bacteria and 4 phyla, 4 classes, and 39 genera of Archaea. Salt-saturated samples were dominated by the bacterial genera Bacillus (51.52%–58.35% relative abundance), Lactococcus (9.52%–10.51%), and Oceanobacillus (8.82%–9.88%) within the Firmicutes phylum (74.81%–80.99%), contrasting with other hypersaline lakes. The dominant Archaea belonged to the Halobacteriaceae family, and in particular, the genera (with an abundance of >10% of communities) Halonotius, Halorubellus, Halapricum, Halorubrum, and Natronomonas. Additionally, we report the presence of Nanohaloarchaeota and Woesearchaeota in Qinghai–Tibet Plateau lakes, which has not been previously documented. Total salinity (especially Mg2+, Cl–, Na+, and K+) mostly correlated with taxonomic distribution across samples. These results expand our understanding of microbial resource utilization within hypersaline lakes and the potential adaptations of dominant microorganisms that allow them to inhabit such environments.

This study aims to assess the hydrogeochemistry of coastal groundwater, the occurrence of 222Rn and 226Ra, and their isotopic response to salinity and associated chemical compositions of groundwater in the coastal Urmia Aquifer (UA) at the western side of Urmia Lake (UL). The results of the PCA show that 87.3% of groundwater chemistry changes are controlled by six principal components. The interaction between groundwater and coastal igneous and metamorphic rocks in eastern areas (next to the UL) results in complex hydrogeochemical conditions than western areas. Based on correlation of U and salinity, some coastal samples display conservative and the others non-conservative behaviors. Differed from most previous studies, 226Ra and 222Rn concentrations in coastal groundwater samples of UA do not show a good correlation with salinity. Given 10% of groundwater 222Rn is originated from host rocks, the radon concentrations recorded in the coastal groundwater samples are relatively in range that can effectively be supplied by the local rocks (5–49 Bq/l). Results of different chemical and isotopic parameters in this area indicate that there is no direct connection between fresh groundwater and UL saltwater. This is because that the hard and thick salty layer in the lakebed acts as an impermeable barrier to prevent the underground hydraulic connection. Results show that removing the salty layer of UL as an option to progress in rehabilitation program of this lake may result in more hydraulic connection between the lake and groundwater resources in some areas.

This study aims to shed light on the seasonal behavior of yttrium and rare earth elements (YREEs) in the Urmia Aquifer (UA), in the immediate vicinity of Urmia Lake (UL) in Iran. Samples of groundwater, collected under dry and wet conditions in coastal wells of UA, suggest a large degree of variability in both YREE abundance and normalized patterns. Although weathering or water-rock interactions (between the surface/groundwater and rock samples) were predicted to be the most probable source in explaining YREEs in groundwater samples, results to the contrary indicate that the groundwater do not inherit aquifer rock-like YREE signatures in the study area; this might be due to the relative stability of YREEs during the process of water-rock interactions, which suggest that methods based on YREEs can be beneficial in discrimination of water sources. Furthermore, findings demonstrated no significant relationship between Ce/Ce* and salinity (0.08 and 0.05 in wet and dry seasons, respectively), and between Eu/Eu* and salinity (0.1 and -0.04 in wet and dry seasons, respectively). Dissimilarity of patterns of YREEs in rock and water samples reveals YREEs as no conservative tracers in determining the UL saltwater intrusion into coastal groundwater. Therefore, the groundwater YREE concentrations and fractionation patterns in UA warrant controlling by coastal aquifer need to be controlled by other chemical weathering, adsorption, desorption, and solution complexation reactions. Finally, comparison of REE concentration values in groundwater samples with corresponding indicative admissible drinking water concentrations (IAC) demonstrated their suitability for drinking purposes.

Salar de Uyuni, situated in the Southwest of the Bolivian Altiplano, is the largest salt flat on Earth. Brines of this athalassohaline hypersaline environment are rich in lithium and boron. Due to the ever- increasing commodity demand, the industrial exploitation of brines for metal recovery from the world’s biggest lithium reservoir is likely to increase substantially in the near future. Studies on the composition of halophilic microbial communities in brines of the salar have not been published yet. Here we report for the first time on the prokaryotic diversity of four brine habitats across the salar. The brine is characterized by salinity values between 132 and 177 PSU, slightly acidic to near-neutral pH and lithium and boron concentrations of up to 2.0 and 1.4 g/L, respectively. Community analysis was performed after sequencing the V3–V4 region of the 16S rRNA genes employing the Illumina MiSeq technology. The mothur software package was used for sequence processing and data analysis. Metagenomic analysis revealed the occurrence of an exclusively archaeal community comprising 26 halobacterial genera including only recently identified genera like Halapricum, Halorubellus and Salinarchaeum. Despite the high diversity of the halobacteria-dominated community in sample P3 (Shannon-Weaver index H’ = 3.12 at 3% OTU cutoff) almost 40% of the Halobacteriaceae-assigned sequences could not be classified on the genus level under stringent filtering conditions. Even if the limited taxonomic resolution of the V3–V4 region for halobacteria is considered, it seems likely to discover new, hitherto undescribed genera of the family halobacteriaceae in this particular habitat of Salar de Uyuni in future.

Agricultural pollution and wastewater effluents from the village of Petrola cause a high pressure over Petrola Lake-aquifer system (Central Spain). The lake is rich in sulfate (SO42−), with concentrations up to 1,280 mmol/L. Petrola lake is considered one of the most symbolic saline wetlands in Castilla-La Mancha Region, due to its geomorphology, hydrology and salinity (up to 109.4 mS/cm). At the water-sediment interface anaerobic conditions and high dissolved organic carbon (up to 21.5 mmol/L) and sulfide production (up to 5 nmol/L) suggest the development of bacterial sulfate reduction processes (BSR). Hydrochemical and isotopic results confirm a mixing trend between high density brine water from the lake and freshwater from the regional groundwater flow. The sulfur origin in the system seems to be linked to sulfide oxidation of Lower Cretaceous sediments (Utrillas Facies) that are rich in sulfide and organic matter. Sulfur and oxygen isotope data show the sulfate-bearing mineral dissolution as the main source of SO42− in surface water. The study concludes that the regulation of the amount of sulfur depends on the relationship between the kinetics of BSR and the hydrodynamic instability driven by the different density of groundwater flow.

The Sambhar Salt Lake is a halite rich athalassohaline basin, provides a unique opportunity for microbial ecologists to study halophiles. The lake has a high proportion of Na+ and Cl− ions making it a hypersaline ecosystem. In the current study, archaea and bacteria from Sambhar Lake were isolated using two cultivation approaches. A total of 449 isolates were obtained, out of which 13 represent archaeal while 12 represent bacterial genera. Natronococcus and Alkalibacillus were found predominant groups among archaea and bacteria, respectively. Apart from the common genera in both the approaches Alteribacillus, Halobacillus, Halorubrum, Lentibacillus, Natronorubrum, Piscibacillus and Thalassobacillus were found only in the samples processed onsite however only three genera Aliidiomarina, Natrinema and Natronolimnobius were isolated when samples were processed in the laboratory after transportation using the same growth conditions. Other than the isolation of diverse group of organisms 13 putative novel taxa with similarity less than 98% were identified using 16S rRNA gene sequencing.

Vannella samoroda n. sp. (Amoebozoa, Vannellida) was isolated from the mouth of the Malaya Samoroda river flowing into Elton, the largest European hypersaline lake (Russia). Among all rivers of the area, it has the highest salt content (ca. 110‰). Amoebae maintained in seawater medium with ca. 77‰ salts concentration had a set of morphological characters typical of Vannella spp.: rounded, fan-shaped, or spatulate locomotive form, floating form with bent, blunt-ended hyaline pseudopodia, and a cell coat consisting of regularly packed palisade elements and scarce simple filaments. Phylogenetic analyses based on SSU rRNA and cytochrome C oxidase subunit 1 genes show that the amoeba is most closely related to Vannella ebro Smirnov, 2001, but represents a distinct species. The clade of V. ebro and V. samoroda branches among marine species of Vannella. The studied species is the first member of the genus Vannella from a continental saline habitat described using molecular data. Interestingly, it has a broad range of salinity tolerance: cells reproduce above 18‰, while survival of a few cells regularly occurs even in highly diluted Prescott and James medium. The normal culture restores itself when PJ medium is substituted with 77‰ seawater medium even after months of experimental incubation.

Imidazolium-based ionic liquids (IL) with short-alkyl side chain such as 1-ethyl-3-methyl-imidazolium chloride ([Emim]Cl) and 1-butyl-3-methyl-imidazolium chloride ([Bmim]Cl) has immense application potential including in lignocellulosic bioenergy production. But they are toxic to most microorganisms, and those isolated from different environments as IL-tolerant have salt tolerance capabilities. This study evaluates the relationship between salt and [Emim]Cl tolerance of microorganisms using different salinity sediments (2–19%) and brines (35%) of India's largest inland hypersaline lake, Sambhar in Rajasthan as the model system. While samples with 2% and 35% salinities do not yield any [Emim]Cl (100 mM) tolerant colonies, others have 6–50% colonies tolerant to the IL. Similar trend was observed with 50 mM [Bmim]Cl. Moderate halophilic isolates of genera Halomonas and Bacillus (growth in 0.7–3.0 M NaCl) isolated from the sediments could grow in as high as 375 mM [Emim]Cl, or 125 mM [Bmim]Cl facilitated by higher synthesis, and uptake of organic osmolytes; and up to 1.7-fold increased activity of active efflux pumps. [Bmim]Cl was more toxic than [Emim]Cl in all performed experiments. [Emim]Cl-adapted cells could trounce IL-induced stress. Interestingly, enrichment with 100 mM [Emim]Cl resulted in increase of IL-tolerant colonies in all sediments including the one with 2% salinity. However, the salt saturated brines (35%) do not yield any such colony even after repeated incubations. Extreme halophilic archaea, Natronomonas (growth in 3.0–4.0 M NaCl) isolated from such brines, were exceedingly sensitive to even 5 mM [Emim]Cl, or 1 mM [Bmim]Cl. Two additional extremophilic archaea, namely Haloferax and Haladaptatus were also sensitive to the tested ILs. Archaeal sensitivity is possibly due to the competitive interaction of [Emim]+ with their acidic proteome (15.4–17.5% aspartic and glutamic acids, against 10.7–12.9% in bacteria) that they maintain to stabilize the high amount of K+ ion accumulated by salt-in strategy. Thus, general salt adaptation strategies of moderate halophilic bacteria help them to restrain toxicity of these ILs, but extremophilic archaea are highly sensitive and demands meticulous use of these solvents to prevent environmental contamination.

The spatiotemporal dynamic of salinity concentration (SC) in saline lakes is strongly dependent on the rate of water flow into the lake, water circulation, wind speed, evaporation rate, and the phenomenon of salt precipitation and dissolution. Although in-situ observations most reliably quantify water quality metrics, the spatiotemporal distribution of such data are typically limited and cannot be readily extrapolated for either long-term projections or extensive areas. Alternatively, remotely sensed imagery has facilitated less expensive and a stronger ability to estimate water quality over a wide range of spatiotemporal resolutions. This study introduces an adaptive learning model that leverages in-situ measurements, satellite imagery, and machine learning algorithms to estimate the spatiotemporal changes of water surface SC in saline lakes. We demonstrate the applicability of the framework by using high-resolution Sentinel-2 and Landsat-8 satellite data in the Lake Urmia (LU), where 130 points were sampled in April and July 2019 for the model calibration and validation purposes. The results showed that Artificial Neural Network (ANN) yields the most accurate relationship between SC and water surface reflectance (R2 = 0.94; NRMSE = 6.9%; MAE = 12.3 ppt) as compared to Adaptive Network-based Fuzzy Inference System (ANFIS), and Multiple Linear Regression (MLR) models. A sharp distinction in SC between the LU’s northern and southern parts was observed during high flows due to the limitation on north–south water mixing imposed by the lake’s middle causeway. Nevertheless, the impact of causeway on water circulation at the other seasons is minimum. A hysteretic relationship was also found between the lake water volume and the lake-averaged SC due to the distinct role of bed-salt dissolution and high evaporation rate at different seasons. A tight agreement between the SC variations in the southern part and the whole lake proved that the southern part dominantly controls SC dynamics in the whole lake.

A Gram-stain-positive, endospore-forming, long rod-shaped, strictly aerobic, moderately halophilic bacterium, designated strain T9BT, was isolated from a brine sample of the hypersaline lake Aran-Bidgol in Iran. Cells of strain T9BT were motile and produced colonies with a brown pigment. Growth occurred between 1.0 and 20 % (w/v) NaCl and the isolate grew optimally at 5.0 % (v/w) NaCl. The optimum pH and temperature for growth of the strain were pH 7.0 and 35 °C, while it was able to grow over pH and temperature ranges of pH 6.0-9.0 and 25-45 °C. Phylogenetic analysis based on the comparison of 16S rRNA gene sequences revealed that strain T9BT is a member of the genus Oceanobacillus. The closest relative to this strain was Oceanobacillus rekensis PT-11T with a similarity of 97.4 %, followed by Oceanobacillus profundus CL-MP28T and Oceanobacillus polygoni SA9T with 97.3 and 97.1 % similarity, respectively. The major cellular fatty acids of the isolate were anteiso-C15 : 0, iso-C14 : 0 and iso-C16 : 0. The polar lipids of strain T9BT consisted of phosphatidylglycerol, diphosphatidylglycerol, three phospholipids and one aminoglycolipid. It contained MK-7 as the predominant menaquinone and meso-diaminopimelic acid in the cell-wall peptidoglycan. The G+C content of the genomic DNA of this strain was 42.9 mol%. Phylogenetic analysis, DNA-DNA hybridization data and phenotypic characteristics allowed strain T9BT to be differentiated from other members of the genus Oceanobacillus. A novel species, Oceanobacillus longus sp. nov., is therefore proposed to accommodate this strain. The type strain is T9BT (=IBRC-M 10703T=LMG 29250T).

Anaerobic enrichments with acetate as electron donor and carbon source, and elemental sulfur as electron acceptor at 4 M NaCl using anaerobic sediments and brines from several hypersaline lakes in Kulunda Steppe (Altai, Russia) resulted in isolation in pure culture of four strains of obligately anaerobic haloarchae growing exclusively by sulfur respiration. Such metabolism has not yet been demonstrated in any known species of Halobacteria, and in the whole archaeal kingdom, acetate oxidation with sulfur as acceptor was not previously demonstrated. The four isolates had nearly identical 16S rRNA gene sequences and formed a novel genus-level branch within the family Halobacteriaceae. The strains had a restricted substrate range limited to acetate and pyruvate as electron donors and elemental sulfur as electron acceptor. In contrast to aerobic haloarchaea, the biomass of anaerobic isolates completely lacked the typical red pigments. Growth with acetate+sulfur was observed between 3–5 M NaCl and at a pH range from 6.7 to 8.0. The membrane core lipids were dominated by archaeols. On the basis of distinct physiological and phylogenetic data, the sulfur-respiring isolates represent a novel species of a new genus in the family Halobacteriaceae, for which the name Halanaeroarchaeaum sulfurireducens gen. nov., sp. nov. is proposed. The type strain of the type species is HSR2T (=JCM 30661T=UNIQEM U935T).

The aim of this study was to isolate a novel esterase from a hypersaline lake by sequence-based metagenomics. The metagenomic DNA was isolated from the enriched hypersaline lake sediment. Degenerate primers targeting the conserved regions of lipolytic enzymes of halophilic microorganisms were used for polymerase chain reaction (PCR) and a whole gene was identified by genome walking. The gene was composed of 783 bp, which corresponds to 260 amino acids with a molecular weight of 28.2 kDa. The deduced amino acid sequence best matched with the esterase from Halomonas gudaonensis with an identity of 91%. Recombinantly expressed enzyme exhibited maximum activity towards pNP-hexanoate with a kcat value of 12.30 s−1. The optimum pH and temperature of the enzyme were found as 9 and 30 °C, respectively. The effects of NaCl, solvents, metal ions, detergents and enzyme inhibitors were also studied. In conclusion, a novel enzyme, named as hypersaline lake “Acigol” esterase (hAGEst), was identified by sequence-based metagenomics. The high expression level, the ability to maintain activity at cold temperatures and tolerance to DMSO and metal ions are the most outstanding properties of the hAGEst.

The dried bed of the world's second largest permanent Hypersaline lake, Lake Urmia, acts as a Hypersaline particle emission source. In the present study we aim to assess the health impact of this disaster and examine the association of Hypersaline particles with total and differential white blood cell counts (WBC) and homocysteine (Hcy), the biomarkers of cardiovascular diseases, in the residents around Lake Urmia. Based on the previous study three regions were selected as clean and polluted regions for ambient particulate matter (APM) from 2008 to 2015. Concentration of APM (PM10, PM2.5 and PM1; particulate matter with aerodynamic diameter of less than 10, 2.5 and 1 µm, respectively) was measured in the selected regions and totally, 123 participants were selected randomly from villagers who have lived in the selected regions for at least eight years. Biomarkers and covariates were measured in the selected regions and were analyzed using multiple linear regression models. We found a statistically significant association between APM and selected biomarkers (Hcy, total WBC, neutrophil, monocyte, lymphocyte and basophile) in the polluted regions. These results are consistent with our hypothesis that long-term exposure to Hypersaline particles originated from drying Urmia Hypersaline Lake is related to increased cardiovascular risk biomarkers. © 2018 Elsevier Inc.

The 12th International Conference on Salt Lake Research was held in Langfang City, China from July 14 to 18, 2014. Fifteen manuscripts of presentations have been retained for publication in this special issue. They are very diverse, covering the biology, physics, chemistry and geology of salt lakes, the history of hydrological research on the Dead Sea, the effects of socioeconomic and environmental policies by stakeholders on human populations, and the increasing salinization of freshwater lakes around the world.

In this paper, we introduced parameterizations of the salinity effects (on heat capacity, thermal conductivity, freezing point and saturated vapor pressure) in a lake scheme integrated in the Weather Research and Forecasting model coupled with the Community Land Model (WRF-CLM). This was done to improve temperature simulation over and in a saline lake and to test the contributions of salinity effects on various water properties via sensitivity experiments. The modified lake scheme consists of the lake module in the CLM model, which is the land component of the WRF-CLM model. The Great Salt Lake (GSL) in the USA was selected as the study area. The simulation was performed from September 3, 2001 to September 30, 2002. Our results show that the modified WRF-CLM model that includes the lake scheme considering salinity effects can reasonably simulate temperature over and in the GSL. This model had much greater accuracy than neglecting salinity effects, particularly in a very cold event when that effect alters the freezing point. The salinity effect on saturated vapor pressure can reduce latent heat flux over the lake and make it slightly warmer. The salinity effect on heat capacity can also make lake temperature prone to changes. However, the salinity effect on thermal conductivity was found insignificant in our simulations.

An extremely halophilic archaeon, strain IC35T, was isolated from a mud sample of the Aran-Bidgol salt lake in Iran. The novel strain was cream, non-motile, rod-shaped and required at least 2.5 M NaCl, but not MgCl2, for growth. Optimal growth was achieved with 3.4 M NaCl and 0.1 M MgCl2. The optimum pH and temperature for growth were pH 7.0 (grew over a pH range of 6.5–9.0) and 40 °C (grew over a temperature range of 30–50 °C), respectively. Analysis of 16S rRNA gene sequences revealed that strain IC35T clustered with species of the genus Halovivax , with sequence similarities of 97.3 %, 96.6 % and 96.3 %, respectively, to Halovivax limisalsi IC38T, Halovivax asiaticus EJ-46T and Halovivax ruber XH-70T. The rpoB′ gene similarities between the novel strain and Halovivax limisalsi IBRC-M 10022T, Halovivax ruber JCM 13892T and Halovivax asiaticus JCM 14624T were 90.2 %, 90.2 % and 89.9 %, respectively. The polar lipid pattern of strain IC35T consisted of phosphatidylglycerol and phosphatidylglycerol phosphate methyl ester; six unknown glycolipids and two minor phospholipids were also observed. The only quinone present was MK-8 (II-H2). The G+C content of the genomic DNA was 63.2 mol%. DNA–DNA hybridization studies (29 % hybridization with Halovivax limisalsi IBRC-M 10022T), as well as biochemical and physiological characterization, allowed strain IC35T to be differentiated from other species of the genus Halovivax . A novel species, Halovivax cerinus sp. nov., is therefore proposed to accommodate this strain. The type strain is IC35T ( = IBRC-M 10256T = KCTC 4050T).

Two proteolytic bacterial strains, BSker2Tand BSker3T, were enriched from sediments of hypersaline alkaline lakes in Kulunda Steppe (Altai, Russia) with chicken feathers as substrate, followed by pure culture isolation on hypersaline alkaline media with casein. The cells were non-motile, filamentous, flexible rods. The isolates were obligately aerobic heterotrophs utilizing proteins and peptides as growth substrates. Both were obligate alkaliphiles, but differed in their pH optimum for growth: pH 9.5-9.8 for Bsker2Tand pH 8.5-8.8 for BSker3T. The salt range for growth of both isolates was between 2 and 4.5 M total Na+ with an optimum at 2.5-3 M. No organic osmolytes were detected in cells of BSker2T, but they accumulated high intracellular concentrations of K+. The polar lipid fatty acids were dominated by unsaturated C16 and C18 species. The 16S rRNA gene phylogeny indicated that both strains belong to the recently proposed phylum Rhodothermaeota. BSker2Tforms a novel genus-level branch, while BSker3Trepresents a novel species-level member in the genus Longimonas. On the basis of distinct phenotypic and genotypic properties, strain BSker2T(=JCM 31342T=UNIQEM U1009T) is proposed to be classified as a representative of a novel genus and species, Natronotalea proteinilyticagen. nov., sp. nov., and strain BSker3T(=JCM 31343T=UNIQEM U1010T) as a representative of a novel species, Longimonas haloalkaliphila sp. nov.

The anostracan Artemia is one of the few organisms that can inhabit hypersaline lakes. In Argentina, this genus is represented by two species: the invasive A. franciscana Kellogg, 1906 and the autochthonous A. persimilis Piccinelli & Prosdocimi, 1968, the latter being the only one recorded in the province of La Pampa. Some of the biological aspects of A. persimilis are known based on laboratory studies, and data on its ecology in natural conditions are scarce. The aim of this work is to present information on the density, biomass, and population structure of A. persimilis in relation to environmental variables in Utracán, a hypersaline lake of the semiarid Central Pampa of Argentina. Water and zooplankton samples were taken monthly from May 2009 until August 2010. The mean density and biomass were 56.98 ind.L-1 (± 106.64) and 1.23 mg.L-1 (± 1.35), respectively. The species was negatively affected by salinity, and it was absent between November and February, when salinity exceeded 320 g.L-1. However, when it was present, even during the months of higher salinity, a high proportion of naupliar stages was found, which could indicate that, in nature, A. persimilis can reproduce with high salinity. Although it has been indicated that A. persimilis could be displaced by A. franciscana, the highest tolerance of the former at low temperatures, which allowed the population to continue reproducing at values close to 3°C, would limit its displacement. However, an increase in the temperature of lakes as a result of global warming could modify this situation and allow the advance of the introduced species to the south. Resumen Los anostracos del género Artemia son algunos de los pocos organismos que pueden habitar los lagos hipersalinos. En Argentina, este género está representado por dos especies: la introducida A. franciscana Kellogg, 1906 y la autóctona A. persimilis Piccinelli & Prosdocimi, 1968, esta última, la única especie registrada en la provincia de La Pampa. Algunos aspectos de la biología de A. persimilis basados en estudios de laboratorio son conocidos, pero la información sobre su ecología en condiciones naturales es muy escasa. El objetivo de este trabajo es presentar información sobre la densidad, biomasa y la estructura de la población de A. persimilis en relación con parámetros ambientales en Utracán, un lago hipersalino de la Pampa Central semiárida de Argentina. Se tomaron muestras mensuales de zooplancton y agua desde mayo de 2009 hasta agosto de 2010. La densidad y biomasa medias a lo largo del estudio fueron 56.98 ind.L-1 (± 106.64) y 1.23 mg.L-1 (± 1.35). La especie fue afectada negativamente por la salinidad, dado que no se registró entre noviembre y febrero, cuando la misma excedió los 320 g.L-1. Sin embargo, cuando estuvo presente, aún en los meses de mayor salinidad se encontró una proporción de estadios naupliares elevada, lo que podría indicar que, en la naturaleza, A. persimilis puede reproducirse con alta salinidad. A pesar de que se ha indicado que A. persimilis podría ser desplazada por A. franciscana, la mayor tolerancia de la primera a bajas temperaturas, que permitió que a valores cercanos a 3°C la población continuara reproduciéndose, limitaría su desplazamiento. Sin embargo, un aumento de la temperatura de los lagos como consecuencia del calentamiento global podría modificar esta situación y permitir el avance de la especie introducida hacia el sur.

A novel halophilic archaeon, designated strain WIIAL99T, was isolated from Lake Meyghan, a hypersaline lake in Iran. Cells of strain WIIAL99T were non-motile, catalase-positive and oxidase-negative. Strain WIIAL99T required at least 2.5 M NaCl and 0.05 M MgCl2 for growth. Optimal growth was achieved at 3.5 M NaCl and 0.1 M MgCl2. The optimum pH and temperature for growth were pH 7.0 and 37–40 °C; it was able to grow at pH 6.0–8.5 and 20–55 °C. Cells lysed in distilled water and the minimal NaCl concentration to prevent cell lysis was 8 % (w/v). The major polar lipids of strain WIIAL99T were phosphatidylglycerol, phosphatidylglycerol phosphate methyl ester, disulfated diglycosyl diether and one unidentified glycolipid. The DNA G+C content of strain WIIAL99T was 66.7 mol%. The closest relative was Natronoarchaeum rubrum JCM 17119T with 98.2 % similarity in the orthologous 16S rRNA gene sequence. Analysis of 16S rRNA and rpoB′ gene sequences indicated that strain WIIAL99T is a member of the genus Natronoarchaeum in the family Halobacteriaceae and forms a distinct cluster. It was concluded that strain WIIAL99T (=IBRC-M 11062T=LMG 29814T) represents a novel species of the genus Natronoarchaeum , for which the name Natronoarchaeum persicum sp. nov. is proposed.

Benthic microbial ecosystems of Laguna La Brava, Salar de Atacama, a high altitude hypersaline lake, were characterized in terms of bacterial and archaeal diversity, biogeochem-istry, (including O2 and sulfide depth profiles and mineralogy), and physicochemical characteristics. La Brava is one of several lakes in the Salar de Atacama where microbial communities are growing in extreme conditions, including high salinity, high solar insolation, and high levels of metals such as lithium, arsenic, magnesium, and calcium. Evaporation creates hypersaline conditions in these lakes and mineral precipitation is a characteristic geomicrobiological feature of these benthic ecosystems. In this study, the La Brava non-lithifying microbial mats, microbialites, and rhizome-associated concretions were compared to each other and their diversity was related to their environmental conditions. All the ecosystems revealed an unusual community where Euryarchaeota, Crenarchaeota, Acetothermia, Firmicutes and Planctomycetes were the most abundant groups, and cyanobacteria, typically an important primary producer in microbial mats, were relatively insignificant or absent. This suggests that other microorganisms, and possibly novel pathways unique to this system, are responsible for carbon fixation. Depth profiles of O2 and sulfide showed active production and respiration. The mineralogy composition was calcium carbonate (as aragonite) and increased from mats to microbialites and rhizome-associated concretions. Halite was also present. Further analyses were performed on representative microbial mats and microbialites by layer. Different taxonomic compositions were observed in the upper layers, with Archaea dominating the non-lithifying mat, and Planctomycetes the microbialite. The bottom layers were similar, with Euryarchaeota, Crenarchaeota and Planctomycetes as dominant phyla. Sequences related to Cyanobacteria were very scarce. These systems may contain previously uncharacterized community metabolisms, some of which may be contributing to net mineral precipitation. Further work on these sites might reveal novel organisms and metabolisms of biotechnological interest., Centro de Investigaciones Geológicas

The Dead Sea is one of the saltiest bodies of water in the world. Observational evidence has been obtained of unexpected short-term water heating in the 2 m uppermost layer of this hypersaline lake, following a sharp drop in solar radiation under weak winds. This was carried out using Dead Sea buoy measurements. Passing frontal cloudiness mixed with significant dust pollution over the Judean Mountains and the Dead Sea, which occurred on March 22, 2013, led to a dramatic drop in noon solar radiation from 860 W m−2 to 50 W m−2. This drop in solar radiation caused a short-term (1-hour) pronounced temperature rise in the uppermost layer of the sea down to 2 m depth. After the sharp drop in noon solar radiation, in the absence of water mixing, buoy measurements showed that the temperature rise in the uppermost layer of the Dead Sea took place for a shorter time and was more pronounced than the temperature rise under the regular diurnal solar cycle. The water heating could be explained by gravitational instability in the skin-surface layer, when the warm surface water with the increased salinity and density submerged, thereby increasing temperature in the layers below.