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The genus Methylomarinum accommodates aerobic motile non-pigmented methanotrophic bacteria, which were isolated from marine habitats and require NaCl for growth. Until recently, this genus contained a single species, M. vadi. Here, we describe a novel Methylomarinum representative, strain Ch1-1T, obtained from the sediments of the River Chernavka at its confluence with the hypersaline Lake Elton, Russia. Strain Ch1-1T was represented by gram-negative, pink-pigmented, motile rods or ovoids, which multiplied by binary fission and possessed the particulate methane monooxygenase (pMMO). These bacteria grew on methane within the temperature range of 5–42°C (optimum at 30–35°C) and at рH 6.3–7.5 (optimum at 6.5–6.8). Growth on methanol was inconsistent. NaCl was required for growth, which was observed in liquid media only within a NaCl concentration range of 0.5–10% (w/v). Best growth was recorded at a NaCl concentration of 3.5–4.0% (w/v). The 16S rRNA gene sequence of strain Ch1-1T displayed 97.09–97.24% similarity to the corresponding gene fragments of described representatives of M. vadi. The genome of strain Ch1-1T was 4.8 Mb in size and contained 3 rRNA operons and about 4400 protein-coding genes, including the gene cluster pmoCAB coding for pMMO, a complete set of genes for the function of the ribulose monophosphate pathway as well as genes necessary for ectoine and sucrose biosynthesis. The DNA G+C content was 50.7 mol %. The average nucleotide identity determined for genomes of strain Ch1-1T and M. vadi IT-4T was 78.8%. Based on the number of genotypic and phenotypic differences, we propose to classify this isolate as representing a novel species of the genus Methylomarinum, M. roseum sp. nov. strain Ch1-1T (=VKM B-3852T = UQM 41855T) is the type strain of the newly proposed species. [ABSTRACT FROM AUTHOR]

Polyhydroxyalkanoates (PHAs), green alternatives to petroleum-derived plastics, possess desired features that make them preferred for various applications. Poly(3-hydroxybutyrate) (PHB), one of the most known representative of PHAs, could be synthesized by haloarchaeal species but their production amounts are relatively low compared to those of poly(3-hydroxybutyrate-co-hydroxyvalerate) (PHBV) obtained by haloarchaea. This is the first report describing an overproduction of PHB by a wild-type halophilic archaeon isolated from southern Tunisia, Chott El Jerid. According to the 16S rRNA gene sequence analysis, the isolate CEJ40-10 was affiliated with the species of the genus Haloarcula (97.5% similarity). Regarding the phylogeny based on the amino acid sequences of the PHA synthase subunits encoded by phaC and phaE, their identities to those from Haloarcula quadrata were 99% and 100%, respectively. This strain could accumulate maximum PHA using 1% (w/v) starch at pH 6, after incubation for 72 h at 37 °C with high salt content (30% NaCl). The replacement of starch with glucose or sugar wastewater lowered the polymer yield. Four extraction methods were performed in order to achieve the maximum efficiency of polymer recovery. Hypochlorite digestion of biomass gave a high recovery yield, reaching 72.8% of its total dry mass. Furthermore, analytical methods such as the Fourier transform infrared (FTIR) spectroscopy, gas chromatography (GC), and UV–visible spectrophotometry indicated that the composition of the polymer was a homopolymer PHB. Our findings showed that Haloarcula sp. strain CEJ40-10 was a potential PHB-candidate for industrial scale production using starchy substrates. [ABSTRACT FROM AUTHOR]

The study presents a multi-proxy archive from hypersaline coastal Lake Chokrak in eastern Crimea, a steppe region which is particularly susceptible to moisture fluctuations. XRF, organic carbon and nitrogen, and palynological analyses are used to reconstruct the evolution of the lake and landscape development around it and to provide information about the driving forces behind those changes, such as climate and human impact. The findings show that the basin was an open marine bay between 7640 and 5500 cal. yr BP. After 5500 cal. yr BP, the low rates of sea-level rise led to gradual infilling of the basin. The prevalence of mesic herb-grass steppe around the site, as well as the expansion of broad-leaved trees in the Crimean mountains, indicate relatively warm and humid climate conditions during the Mid-Holocene. Elemental proxies and marine NPPs point to a transition to lagoonal conditions from 4270 cal. yr BP. The progressive shallowing of the basin was accompanied by the spread of more xeric Artemisia -grass steppe, which suggests a shift to arid conditions. The occurrence of cereal pollen from 3660 cal. yr BP may indicate the first signs of cultivation in the study area. The active build-up of a sand barrier from 3000 cal. yr BP led to a gradual separation of the basin from the sea. By 900 cal. yr BP, the fully-formed sand barrier resulted in a transformation of the lagoon into a hypersaline lake. The closing of the lagoon was accompanied by an expansion of halophytic communities around the site. Human-induced vegetation changes became more pronounced with the development of agrarian and pastoral activities around the site from ca. 750 cal. yr BP. [ABSTRACT FROM AUTHOR]

Urmia Lake in NW Iran was the world’s second largest hypersaline lake until three decades ago, when it began to lose ~ 90% of its surface area due to dwindling water input and enhanced evaporation. To help discern the role of natural vs anthropogenic factors in the rapid demise of Urmia Lake, we present a high-resolution, multi-proxy reconstruction of climate, and hydrological variability from the lake’s sediments. We identify several episodes of wet and dry conditions over the past 11,300 years, and an atmospheric teleconnection between the climate of the interior of West Asia and the North Atlantic region. Estimates of mean annual precipitation based on chemical weathering indices range between 174 and 401 mm year−1 during the Holocene. A combination of geochemical proxies, pollen reconstruction, and the absence of any evaporite horizons throughout the Holocene period point to the prevailing role of human impact on the current vanishing of Urmia Lake. [ABSTRACT FROM AUTHOR]

Abstract Lake Hillier is a hypersaline lake known for its distinctive bright pink color. The cause of this phenomenon in other hypersaline sites has been attributed to halophiles, Dunaliella, and Salinibacter, however, a systematic analysis of the microbial communities, their functional features, and the prevalence of pigment-producing-metabolisms has not been previously studied. Through metagenomic sequencing and culture-based approaches, our results evidence that Lake Hillier is composed of a diverse set of microorganisms including archaea, bacteria, algae, and viruses. Our data indicate that the microbiome in Lake Hillier is composed of multiple pigment-producer microbes, including Dunaliella, Salinibacter, Halobacillus, Psychroflexus, Halorubrum, many of which are cataloged as polyextremophiles. Additionally, we estimated the diversity of metabolic pathways in the lake and determined that many of these are related to pigment production. We reconstructed complete or partial genomes for 21 discrete bacteria (N = 14) and archaea (N = 7), only 2 of which could be taxonomically annotated to previously observed species. Our findings provide the first metagenomic study to decipher the source of the pink color of Australia’s Lake Hillier. The study of this pink hypersaline environment is evidence of a microbial consortium of pigment producers, a repertoire of polyextremophiles, a core microbiome and potentially novel species.

The results of studying the influence of the main natural environmental factors on the interannual (2017–2021) and seasonal (from April to October) zooplankton dynamics of the large hypersaline Lake Kulunda located in the Kulunda steppe (Altai krai, Russia) are presented. The relationship of 13 main indicators of the structure of zooplankton (number and biomass in total, the main taxonomic groups: rotifers, copepods, cladocerans, and branchiopods, as well as different stages of the life cycle of Artemia) with the main hydrophysical and hydrochemical indicators (temperature, density, salinity, and pH of water) was analyzed separately by monthly and average annual (for the growing season) values. The influence of the studied factors on the characteristics of the brine shrimp population (number, biomass, and age structure), which dominated the zooplankton of this lake, was analyzed in more detail. It was revealed that the hydrophysical and hydrochemical regimes of the lake in different years are subject to significant changes and are reflected in the indicators of zooplankton. Changes in the structure of zooplankton under the influence of natural factors are mainly due to the stimulating effect of an increase in water mineralization on the Artemia population and its depressing effect on the brackish fauna. With a decrease in water salinity less than 100 g/dm3 since 2017 (127 g/m3) to 2021 (96 g/dm3) maximum (summer) Artemia biomass decreased from 167 to 17.7 g/m3. At the same time, the maximum biomass of rotifers, cladocerans, and copepods increased from 0.003, 0, and 0.63 to 6.21, 1.35, and 2.65 g/m3 respectively. [ABSTRACT FROM AUTHOR]

Saline and hypersaline waters are one of the most peculiar ecosystems of our planet, characterized by extreme life conditions. Despite their worldwide distribution, the diversity and abundance of protist communities in these ecosystems remain poorly studied. Here, we analyze planktonic communities of protists sampled across 38 saline and hypersaline water environments (2–390‰) from arid climatic zones of the South Urals and Crimea in light of environmental data using high-throughput 18S rDNA amplicon sequencing. A total of 9 eukaryotic supergroups, 34 phyla, 104 classes, 184 orders, 315 families and 548 genera have been identified. We revealed significant differences in the taxonomic structure of protist communities depending on salinity, geographic location and pH. The protist communities demonstrated linear regression of richness and diversity and growth of the percentage of unclassified Eukaryota (up to 43%) with the increase in salinity. Centrohelids demonstrated the ability to inhabit a broad range of salinities, up to 320‰, which is four times higher than previously reported. Centrohelid species Pinjata ruminata and Yogsothoth sp. are assumed to be specifically adapted to salinity of 3–210‰. The obtained results provide insight into the taxonomy and diversity of protists in saline and hypersaline environments and highlight the great potential for the discovery of new taxa due to the large number of unclassified 18S rDNA sequences. [ABSTRACT FROM AUTHOR]

Lake Hillier is a hypersaline lake known for its distinctive bright pink color. The cause of this phenomenon in other hypersaline sites has been attributed to halophiles, Dunaliella, and Salinibacter, however, a systematic analysis of the microbial communities, their functional features, and the prevalence of pigment-producing-metabolisms has not been previously studied. Through metagenomic sequencing and culture-based approaches, our results evidence that Lake Hillier is composed of a diverse set of microorganisms including archaea, bacteria, algae, and viruses. Our data indicate that the microbiome in Lake Hillier is composed of multiple pigment-producer microbes, including Dunaliella, Salinibacter, Halobacillus, Psychroflexus, Halorubrum, many of which are cataloged as polyextremophiles. Additionally, we estimated the diversity of metabolic pathways in the lake and determined that many of these are related to pigment production. We reconstructed complete or partial genomes for 21 discrete bacteria (N = 14) and archaea (N = 7), only 2 of which could be taxonomically annotated to previously observed species. Our findings provide the first metagenomic study to decipher the source of the pink color of Australia's Lake Hillier. The study of this pink hypersaline environment is evidence of a microbial consortium of pigment producers, a repertoire of polyextremophiles, a core microbiome and potentially novel species. [ABSTRACT FROM AUTHOR]

The energy balance approach helps to understand the limits within which the 'predator–prey' relationship can form, but cannot explain the formation of trophic links in natural multispecies systems. A time balance approach to the study of feeding has been developed to complement it. In the hypersaline Lake Moynaki (Crimea) which has a simple food web, there is one omnivorous species, Gammarus aequicauda, and two abundant prey, planktonic Moina salina and benthic Baeotendipes noctivagus. The size of M. salina ranges from 1.0 to 1.2 mm, and the size of B. noctivagus larvae from 9.0 to 10.0 mm. In experiments, elements of time balance were evaluated during feeding of G. aequicauda in the presence of both prey species, i.e., the duration of time spent searching before capture, handling prey, and resting between attempts to eat a chironomid larva. In all experiments, G. aequicauda consumed both kinds of prey. The maximum predation rate of G. aequicauda on the smaller sized M. salina was limited by searching and handling time, but on the larger B. noctivagus it was limited by digestion time. Feeding solely on chironomid larvae may well satisfy the energy needs of G. aequicauda. However, the food ration of G. aequicauda may be 50% higher if it feeds in the presence of both prey species than if feeding only on chironomid larvae. The presence of chironomid larvae more than halved the consumption of M. salina, compared to when cladocerans were the only prey. [ABSTRACT FROM AUTHOR]

The results of lithological and mineralogical studies of the Holocene bottom sediments from the shallow hypersaline (mineralization up to 282 g/L) Bolshoi Bagan Lake, located in the East Baraba Lowland (southwestern Siberia), are presented. The research methods included X-ray diffractometry (XRD), infrared spectroscopy, laser grain size analysis, scanning electron microscopy, elemental composition study, and radiocarbon (14C AMS) dating. It was found that intensive authigenic minerogenesis occurred in the lake basin during the Holocene. Halite, gypsum, and carbonates dominate among the newly formed mineral phases. Mg-calcites with different Mg contents, excess-Ca dolomites, aragonite, and occasionally Mg-siderite have been established in the assemblage of carbonate minerals by the mathematical modeling of complex XRD patterns. The mineralogical and crystallochemical studies, supplemented by the results of other analyses, allowed us to identify four stages of the evolution of Bolshoi Bagan Lake in the Holocene, due to variations in the regional climate. The boundaries of the stages generally correspond to the boundaries of the climatic stratigraphical phases by the Blytt–Sernander classification: stage I (the end of the Boreal), lake formation, humid climate; stage II (Atlantic), climate drying, shallowing of the lake; stage III (Subboreal), unstable climate, frequent change of conditions; stage IV (Sub-Atlantic), moderately cool and dry climate. The mineralogical signals of the global climatic Bond events in southwestern Siberia have been identified. [ABSTRACT FROM AUTHOR]

Simple Summary: The Laguna Negra is a high-altitude hypersaline lake located in the Puna region in Argentina, hosting microbial mats and modern stromatolites, microbially formed rocks found throughout the geological record. Some recent studies have shown the relevance of the lakes in this region for (i) the discovery of new extremophiles, particularly those tolerant to high UV and, furthermore, (ii) the study of biosignatures in stromatolites. In this work, a detailed survey, layer by layer, of the microbial diversity of the most widespread microbial mat in the Laguna Negra was reported, to unravel the spatial arrangement of the microbial community. The results reveal the vertical distribution of the main prokaryotic microbial taxa, and underline abundant Deinococcus-Thermus at the top of the microbial mat with high amounts of deinoxanthin, which may help the total community to cope with high UV radiation. This study allows a better understanding of the community strategies to thrive under environmental stressors in the Laguna Negra and its counterparts in the Altiplano-Puna region. The Altiplano-Puna region is a high-altitude plateau in South America characterized by extreme conditions, including the highest UV incidence on Earth. The Laguna Negra is a hypersaline lake located in the Catamarca Province, northwestern Argentina, where stromatolites and other microbialites are found, and where life is mostly restricted to microbial mats. In this study, a particular microbial mat that covers the shore of the lake was explored, to unravel its layer-by-layer vertical structure in response to the environmental stressors therein. Microbial community composition was assessed by high-throughput 16S rRNA gene sequencing and pigment content analyses, complemented with microscopy tools to characterize its spatial arrangement within the mat. The top layer of the mat has a remarkable UV-tolerance feature, characterized by the presence of Deinococcus-Thermus and deinoxanthin, which might reflect a shielding strategy to cope with high UV radiation. Chloroflexi and Deltaproteobacteria were abundant in the second and third underlying layers, respectively. The bottom layer harbors copious Halanaerobiaeota. Subspherical aggregates composed of calcite, extracellular polymeric substances, abundant diatoms, and other microorganisms were observed all along the mat as the main structural component. This detailed study provides insights into the strategies of microbial communities to thrive under high UV radiation and hypersalinity in high-altitude lakes in the Altiplano-Puna region. [ABSTRACT FROM AUTHOR]

Nitrate-reducing Fe(II)-oxidizing (NRFeOx) microorganisms contribute to nitrogen, carbon, and iron cycling in freshwater and marine ecosystems. However, NRFeOx microorganisms have not been investigated in hypersaline lakes, and their identity, as well as their activity in response to salinity, is unknown. In this study, we combined cultivation-based most probable number (MPN) counts with Illumina MiSeq sequencing to analyze the abundance and community compositions of NRFeOx microorganisms enriched from five lake sediments with different salinities (ranging from 0.67 g/L to 346 g/L). MPN results showed that the abundance of NRFeOx microorganisms significantly (P, 0.05) decreased with increasing lake salinity, from 7.55 - 103 to 8.09 cells/g dry sediment. The community composition of the NRFeOx enrichment cultures obtained from the MPNs differed distinctly among the five lakes and clustered with lake salinity. Two stable enrichment cultures, named FeN-EHL and FeN-CKL, were obtained from microcosm incubations of sediment from freshwater Lake Erhai and hypersaline Lake Chaka. The culture FeN-EHL was dominated by genus Gallionella (68.4%), while the culture FeN-CKL was dominated by genus Marinobacter (71.2%), with the former growing autotrophically and the latter requiring an additional organic substrate (acetate) and Fe(II) oxidation, caused to a large extent by chemodenitrification [reaction of nitrite with Fe(II)]. Short-range ordered Fe(III) (oxyhydr)oxides were the product of Fe(II) oxidation, and the cells were partially attached to or encrusted by the formed iron minerals in both cultures. In summary, different types of interactions between Fe(II) and nitrate-reducing bacteria may exist in freshwater and hypersaline lakes, i.e., autotrophic NRFeOx and chemodenitrification in freshwater and hypersaline environments, respectively. [ABSTRACT FROM AUTHOR]

In 2018–2019, a year-round study of the hypersaline Moynaki Lake, western Crimea, was conducted. In mid-summer 2018, along with Moina salina, which had previously been reported from the lake, the year-round presence of further two cladoceran species, Chydorus sphaericus and Bosmina (Eubosmina) coregoni, was recorded there for the first time. None of those species had ever been registered from hypersaline waters anywhere else. Their introduction seems to have occurred because of a salinity decrease, even though the modern level of salinity has been observed the same level for at least the past 20 years. The presently highly eutrophic environment of Moynaki Lake is probably sufficiently energy-rich to sustain cladoceran osmo-adaptations. [ABSTRACT FROM AUTHOR]

Sambhar Salt Lake, situated in the state of Rajasthan, India is a unique temperate hypersaline ecosystem. Exploration of the salt lake microbiome will enable us to understand microbiome functioning in nutrient-deprived extreme conditions, as well as enrich our understanding of the environment-specific microbiome evolution. The current study has been designed to explore the Sambhar Salt Lake microbiome with a culture-independent multi-omics approach to define its metagenomic features and prevalent metabolic functionaries. The rRNA feature and protein feature-based phylogenetic reconstruction synchronously (R = 0.908) indicated the dominance of the archaea (Euryarchaeota) and bacteria (Firmicutes, Proteobacteria, Bacteroidetes, and Actinobacteria). Metabolic reconstruction identified selective enrichment of the protein features associated with energy harvesting and stress tolerance (osmotic, oxidative, metal/metalloid, heat/cold, antibiotic, and desiccation). Metabolites identified with metabolome analysis confirmed physiological adaptation of the lake microbiome within a hypersaline and nutrient-deprived environment. Comparative metagenomics of the 212 metagenomes representing freshwater, alkaline, and saline ecosystem microbiome indicated the selective enrichment of the microbial groups and genetic features. The current study elucidates microbiome functioning within the nutrient-deprived harsh ecosystems. In summary, the current study harnessing the strength of multi-omics and comparative metagenomics indicates the environment-specific microbiome evolution. [ABSTRACT FROM AUTHOR]

Sambhar Salt Lake, situated in the state of Rajasthan, India is a unique temperate hypersaline ecosystem. Exploration of the salt lake microbiome will enable us to understand microbiome functioning in nutrient-deprived extreme conditions, as well as enrich our understanding of the environment-specific microbiome evolution. The current study has been designed to explore the Sambhar Salt Lake microbiome with a culture-independent multi-omics approach to define its metagenomic features and prevalent metabolic functionaries. The rRNA feature and protein feature-based phylogenetic reconstruction synchronously (R = 0.908) indicated the dominance of the archaea (Euryarchaeota) and bacteria (Firmicutes, Proteobacteria, Bacteroidetes, and Actinobacteria). Metabolic reconstruction identified selective enrichment of the protein features associated with energy harvesting and stress tolerance (osmotic, oxidative, metal/metalloid, heat/cold, antibiotic, and desiccation). Metabolites identified with metabolome analysis confirmed physiological adaptation of the lake microbiome within a hypersaline and nutrient-deprived environment. Comparative metagenomics of the 212 metagenomes representing freshwater, alkaline, and saline ecosystem microbiome indicated the selective enrichment of the microbial groups and genetic features. The current study elucidates microbiome functioning within the nutrient-deprived harsh ecosystems. In summary, the current study harnessing the strength of multi-omics and comparative metagenomics indicates the environment-specific microbiome evolution.

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.

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 (rbc L, cbb L), formaldehyde assimilation (SHMT), and nitric oxide reduction (Nor Q) shed light on the roles played by GSL viruses in biogeochemical cycles of global relevance. [ABSTRACT FROM AUTHOR]

Cladophora spp. constantly or periodically form floating and benthic mats in Crimean hypersaline lakes and lagoons. In 2017–2018, characteristics of the Cladophora mats and the microalgae on Cladophora filaments were studied employing field research and microscopy. The whole Cladophora mat has a vertical structure, including the upper and lower layers of the floating mat and benthic mat. In total, 50 species of microalgae were found: 40 of them belonged to Bacillariophyta (Bacillariophyceae and Mediophyceae), two to Haptophyta (Coccolithophyceae), four to Miozoa (Dinophyceae), one to Chlorophyta (Zygnematophyceae) and three to Cyanobacteria (Cyanophyceae). Floating layers of the mat differed significantly in species composition from the benthic mat. The total abundance of microalgae and their biomass on Cladophora (per unit area of filaments) varied widely within sampling sites from 3.79 × 106 to 5.04 × 108 cells m–2 and 2.6 to 2197.8 mg m–2. The total mass of microalgae achieved more than 32% of the mass of Cladophora, averaging 7.7% (standard deviation = 13.3). [ABSTRACT FROM AUTHOR]

Abstract Lacustrine stromatolites were widespread in the Miocene Wudaoliang Group (stromatolites of the Wudaoliang Group), northern Tibetan Plateau; but only at one location nearby the Wudaoliang Town, they occurred intensively in thick, laterally traceable beds (Wudaoliang stromatolites). Although deposited in lacustrine environment, the lack of fossils in these rocks hampers determining whether the stromatolites formed in freshwater or saline conditions. To address this problem, and in an attempt to identify criteria to distinguish differences of freshwater and saline conditions, we studied the laminae microfabrics, stable carbon and oxygen isotope ratios, rare earth element patterns and biomarkers of the stromatolites. These stromatolites can be divided into fenestral stromatolites and agglutinated stromatolites. The fabric of fenestral stromatolites is formed by microcrystalline carbonate enclosing spar-cemented, angular crystal traces. Essentially, this fabric is interpreted as pseudomorph after former formed evaporite crystals. Faecal pellets identical to that of the present-day brine shrimp Artemia, lack of other eukaryotic fossils, and stable isotopic signals point to a shallow, evaporation-dominated hypersaline lake setting. Covariation of carbon and oxygen isotopes indicates hydrologically closed conditions of the Miocene lake on northern Tibetan Plateau. However, if compared to other lacustrine carbonates of the Wudaoliang Group, the high δ13C values of the investigated Wudaoliang stromatolites reveal an additional photosynthetic effect during the deposition of the stromatolites. Furthermore, although no direct evidence is available from field observations and microfabrics, a positive europium anomaly of Wudaoliang stromatolites indicates that a palaeo-hydrothermal inflow system had existed in the outcrop area. These new results favour a hypersaline lake setting subject to hot spring inflow for the Wudaoliang stromatolites, in contrast to earlier interpretations suggesting a freshwater lake setting (e.g. Yi et al., Journal of Mineralogy and Petrology 28: 106–113, 2008; Zeng et al., Journal of Mineralogy and Petrology 31: 111–119, 2011). This approach may be appropriate for other lacustrine, unfossiliferous microbialites in settings where the environmental conditions are difficult to determine.

The ecosystems of hypersaline waters are characterized by the simplified trophic webs with the 'loss' of predators. In the absence of predators, their role can be effectively performed by omnivorous as Gammaridae species. In Lake Moynaki, a small hypersaline lake, Gammarus aequicauda is one of the most abundant animal species along with chironomid larvae Baeotendipes noctivagus. Both these species are promising objects to use in polyaquaculture, and this adds an importance to know their trophic relations. To analyse G. aequicauda feeding on B. noctivagus, the field and experimental studies were conducted in 2018 and 2019. In two habitats (Ruppia thickets and free water), the abundance of both species significantly differed, and in the thickets of Ruppia, the Gammarus abundance was higher, and of chironomid larvae was less. Taking into account our experimental results and chironomid larvae abundance in the lake during the study period (from 460 to 3,200 ind./m2), the authors conclude that larvae abundance did not limit the rate of their consumption in the lake by G. aequicauda, and one can consume up to 4 larvae per day. Thus, G. aequicauda could receive a diet of about 45% of their weight consuming about 2% of the available larvae daily in areas without the marine grass Ruppia thickets. In Ruppia thickets, chironomid larvae are not important food of G. aequicauda because the Ruppia leaves play a more important role in gammarid diet. With sufficient plant food resources, G. aequicauda can be successfully cultivated together with chironomid larvae. [ABSTRACT FROM AUTHOR]

The Altiplano-Puna region is a high-altitude plateau in South America characterized by extreme conditions, including the highest UV incidence on Earth. The Laguna Negra is a hypersaline lake located in the Catamarca Province, northwestern Argentina, where stromatolites and other microbialites are found, and where life is mostly restricted to microbial mats. In this study, a particular microbial mat that covers the shore of the lake was explored, to unravel its layer-by-layer vertical structure in response to the environmental stressors therein. Microbial community composition was assessed by high-throughput 16S rRNA gene sequencing and pigment content analyses, complemented with microscopy tools to characterize its spatial arrangement within the mat. The top layer of the mat has a remarkable UV-tolerance feature, characterized by the presence of Deinococcus-Thermus and deinoxanthin, which might reflect a shielding strategy to cope with high UV radiation. Chloroflexi and Deltaproteobacteria were abundant in the second and third underlying layers, respectively. The bottom layer harbors copious Halanaerobiaeota. Subspherical aggregates composed of calcite, extracellular polymeric substances, abundant diatoms, and other microorganisms were observed all along the mat as the main structural component. This detailed study provides insights into the strategies of microbial communities to thrive under high UV radiation and hypersalinity in high-altitude lakes in the Altiplano-Puna region.

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. [ABSTRACT FROM AUTHOR]

Gammarus aequicauda (Amphipoda) and Moina salina (Cladocera) are dominant species and promising objects for aquaculture in hypersaline lakes. In the Crimean hypersaline lake Moynaki, population dynamics of their abundance was studied and experiments on feeding were also done. In 2018 and 2019, the average concentrations of G. aequicauda and M. salina differed between the thickets of sea grass Ruppia and the areas without Ruppia. The concentration of G. aequicauda in the thickets was on average from 52 to 126 times higher than in the Ruppia‐free areas. Moina demonstrated the opposite trend. There was a significant negative correlation between the abundances of these species in the Ruppia thickets (R = −0.746, p =.005). The experimental results on trophic relation showed that the amount of Moina eaten by one G. aequicauda varied from 0.04 to 9.80 ind./hr and depended on the average Moina concentration. Calculation showed that the gammarid population consumed about 1.0%–1.5% of available preys per day. Gammarids were able to graze up to 60%–65% of the Moina population in 10 days. To develop integrated multi‐trophic aquaculture in saline/hypersaline waters, character of 'gammarus–moina' trophic relation and the biological peculiarities of these species must be taken into account. [ABSTRACT FROM AUTHOR]

Saline lakes are subject to numerous environmental impacts related to human activities, changing the chemical and biological natural conditions of the ecosystem. Sustainable development depends on the conservation of such delicate saline ecosystems, which may hold distinctive biodiversity. Pollution is one of the major threats to surface water bodies, for example by increasing nutrient contents and organic pollutants, including endocrine disrupting chemicals. Microbially mediated redox processes exert a fundamental control on nutrient turnover and contaminant removal. This study examines the influence of land use on the distribution of endocrine disrupting chemicals as well as on the microbial community composition in lacustrine sediments from Pétrola saline Lake (SE Spain). The lake is impacted by anthropogenic activities (agriculture, farming, mining and urban wastewater spills). Applying chemical and molecular tools (sequencing of 16S rRNA gene) showed a clear influence of land use on the chemistry and bacterial abundance of the lake sediments. The sampling points closer to wastewater outflows and mining ponds (2635, 2643 and 2650) showed fewer numbers and types of endocrine disrupting chemicals as well as a smaller number of families in the microbial community. These findings improve our understanding of how land use affects both water chemistry and the abundance of organisms responsible for biogeochemical cycles. [ABSTRACT FROM AUTHOR]

The large use of conventional plastics has resulted in serious environmental problems. Polyhydroxyalkanoates represent a potent replacement to synthetic plastics because of their biodegradable nature. This study aimed to screen bacteria and archaea isolated from an extreme environment, the salt lake Chott El Jerid for the accumulation of these inclusions. Among them, two archaeal strains showed positive results with phenotypic and genotypic methods. Phylogenetic analysis, based on the 16S rRNA gene, indicated that polyhydroxyalkanoate (PHA)-producing archaeal isolates CEJGTEA101 and CEJEA36 were related to Natrinema altunense and Haloterrigena jeotgali, respectively. Gas chromatography and UV-visible spectrophotometric analyses revealed that the PHA were identified as polyhydroxybutyrate and polyhydroxyvalerate, respectively. According to gas chromatography analysis, the strain CEJGTEA101 produced maximum yield of 7 wt % at 37 °C; pH 6.5; 20% NaCl and the strain CEJEA36 produced 3.6 wt % at 37 °C; pH 7; 25% NaCl in a medium supplemented with 2% glucose. Under nutritionally optimal cultivation conditions, polymers were extracted from these strains and were determined by gravimetric analysis yielding PHA production of 35% and 25% of cell dry weight. In conclusion, optimization of PHA production from inexpensive industrial wastes and carbon sources has considerable interest for reducing costs and obtaining high yield. [ABSTRACT FROM AUTHOR]

Questions: What are the plant communities and vegetation pattern on shorelines of a hypersaline desiccating lake and which environmental factors influence the zonation pattern of these communities? How is the species richness along salt and moisture gradients? Which plant communities and rare species are threatened by the impact of lake shrinkage? Which advice can be offered for the management and restoration of the area? Study area: Lake Urmia, NW Iran, one of the world's largest saltwater lakes. Methods: We established 14 transects with 174 relevés in different parts of the lake and collected soil samples. TWINSPAN was used for vegetation classification and NMDS for ordination. Results: We distinguished 27 plant communities and described as new the associations Salicornio iranicae-Bolboschoenetum affinis, Tamaricetum octandrae, Salicornietum iranicae, Climacopteretum crassae, Suaedo altissimae-Climacopteretum crassae and the Atriplici leucocladae-Caroxyletum dendroidis. We present an overview of the syntaxa and illustrate typical zonation patterns of the lake's salt marsh vegetation under current conditions of desiccation. Conclusions: The vegetation pattern and vegetation dynamics of the area is seriously affected by the hydrological changes around Lake Urmia. Fragmentation of wetland plant communities due to water shortage, increasing disturbance and invasion of ruderal species affect the floristic composition of the lakeside. Increasing soil salinity and decreasing moisture lead to area loss or even disappearance of certain plant communities. Plant communities with C4 annuals or pioneer ruderal species are developing or spreading in sites with low soil salinity or on sandy soils. We strongly recommend vegetation monitoring using permanent plots to improve the predictability of succession trends. Groundwater exploitation, unsustainable use of water resources in the catchment area, any further disturbance in the lakeside area including grazing and artificial plantation activities need to be prohibited. [ABSTRACT FROM AUTHOR]

The sedimentary record of the Dead Sea provides an exceptional high-resolution archive of past climate changes in the drought-sensitive eastern Mediterranean-Levant, a key region for the development of humankind at the boundary of global climate belts. Moreover, it is the only deep hypersaline lake known to have deposited long sequences of finely laminated, annually deposited sediments (i.e. varves) of varied compositions, including aragonite, gypsum, halite and clastic sediments. Vast efforts have been made over the years to decipher the environmental information stored in these evaporitic-clastic sequences spanning from the Pleistocene Lake Amora to the Holocene Dead Sea. A general characterisation of sediment facies has been derived from exposed sediment sections, as well as from shallow- and deep-water sediment cores. During high lake stands and episodes of positive water budget, mostly during glacial times, alternating aragonite and detritus laminae ('aad' facies) were accumulated, whereas during low lake stands and droughts, prevailing during interglacials, laminated detritus ('ld' facies) and laminated halite ('lh' facies) dominate the sequence. In this paper, we (i) review the three types of laminated sediments of the Dead Sea sedimentary record ('aad', 'ld' and 'lh' facies), (ii) discuss their modes of formation, deposition and accumulation, and their interpretation as varves, and (iii) illustrate how Dead Sea varves are utilized for palaeoclimate reconstructions and for establishing floating chronologies. Image 1 • The Dead Sea is the only deep hypersaline lake with varved sediments. • The chronological and paleoclimatic value of Dead Sea varves is demonstrated. • The interpretation of alternating aragonite-detritus laminae as varves is evaluated. • Lake monitoring confirms the interpretation of laminated halite as varves. • Distinguishing between annual and non-annual laminations requires micro-facies analyses. [ABSTRACT FROM AUTHOR]

Abstract The sediment–water transition zone in an aquatic system is key role to the distribution of contaminants between the surface water and sediment pore water. Maharlu Lake is a seasonal hypersaline lake in the central part of the Maharlu Basin in Southern Iran. Wastewater of various types produced within the basin is released into the seasonal freshwater rivers that ultimately drain into the lake. Samples were collected through one complete period of the lake water-level fluctuation. Lake surface water and shallow sediment pore water samples were collected three times at three piezometric stations at different distances from the river inflow points. Lake sediment samples were collected twice, and water samples from the inflowing rivers were collected five times. Changes in surface runoff and agricultural wastewater inflows were responsible for seasonal hydrochemical changes and changes in the As concentrations in the inflowing rivers. Data from the stations close to the river inflows indicated that the dissolved As concentrations across the sediment–water interface in Maharlu Lake are mostly controlled by evaporation and interactions between the surface water and shallow pore water. However, data from the station far from the freshwater inflows indicated that the brine and precipitated evaporites were at equilibrium and redox processes (e.g., iron (hydr)oxide dissolution and secondary sulphide precipitation) control the dissolved As concentration in pore water. The results confirmed the role of lake water evaporation in As enrichment and As sequestration by secondary sulphide minerals in sediment below the sediment–water interface. Climate change may alter the lake chemistry and As behavior in near future. Highlights • Measured total arsenic concentration in inflow rivers water, surface/pore water and shallow sediment in playa salt lake. • Investigate the distribution of arsenic across the sediment-water interface. • Hydrological processes controls dissolved arsenic concentration at area of lake near to the inflowing rivers. • Redox reactions controls dissolved arsenic concentration at area of lake far away from the inflowing rivers. • As in inflow rivers and surface/pore wtar of lake changes seasonally and inter-annually. [ABSTRACT FROM AUTHOR]

Saline lakes are subject to numerous environmental impacts related to human activities, changing the chemical and biological natural conditions of the ecosystem. Sustainable development depends on the conservation of such delicate saline ecosystems, which may hold distinctive biodiversity. Pollution is one of the major threats to surface water bodies, for example by increasing nutrient contents and organic pollutants, including endocrine disrupting chemicals. Microbially mediated redox processes exert a fundamental control on nutrient turnover and contaminant removal. This study examines the influence of land use on the distribution of endocrine disrupting chemicals as well as on the microbial community composition in lacustrine sediments from Pétrola saline Lake (SE Spain). The lake is impacted by anthropogenic activities (agriculture, farming, mining and urban wastewater spills). Applying chemical and molecular tools (sequencing of 16S rRNA gene) showed a clear influence of land use on the chemistry and bacterial abundance of the lake sediments. The sampling points closer to wastewater outflows and mining ponds (2635, 2643 and 2650) showed fewer numbers and types of endocrine disrupting chemicals as well as a smaller number of families in the microbial community. These findings improve our understanding of how land use affects both water chemistry and the abundance of organisms responsible for biogeochemical cycles.

The large use of conventional plastics has resulted in serious environmental problems. Polyhydroxyalkanoates represent a potent replacement to synthetic plastics because of their biodegradable nature. This study aimed to screen bacteria and archaea isolated from an extreme environment, the salt lake Chott El Jerid for the accumulation of these inclusions. Among them, two archaeal strains showed positive results with phenotypic and genotypic methods. Phylogenetic analysis, based on the 16S rRNA gene, indicated that polyhydroxyalkanoate (PHA)-producing archaeal isolates CEJGTEA101 and CEJEA36 were related to Natrinema altunense and Haloterrigena jeotgali, respectively. Gas chromatography and UV-visible spectrophotometric analyses revealed that the PHA were identified as polyhydroxybutyrate and polyhydroxyvalerate, respectively. According to gas chromatography analysis, the strain CEJGTEA101 produced maximum yield of 7 wt % at 37 °C; pH 6.5; 20% NaCl and the strain CEJEA36 produced 3.6 wt % at 37 °C; pH 7; 25% NaCl in a medium supplemented with 2% glucose. Under nutritionally optimal cultivation conditions, polymers were extracted from these strains and were determined by gravimetric analysis yielding PHA production of 35% and 25% of cell dry weight. In conclusion, optimization of PHA production from inexpensive industrial wastes and carbon sources has considerable interest for reducing costs and obtaining high yield.

A novel halophilic bacterium, strain 71-i T , was isolated from Inche-Broun hypersaline lake in Golestan province, in the north of Iran. It was a Gram-stain-negative, non-endospore forming, rod-shaped bacterium. It grew at 4-40 °C (optimum 30 °C), pH 6.0-11.0 (optimum pH 7.5) and with 0.5-15 % (w/v) NaCl [optimum 3 % (w/v) NaCl]. The results of phylogenetic analyses based on the 16S rRNA gene sequence comparison indicated its affiliation to the genus Marinobacter and the low percentage of identity with the most closely related species (97.5 %), indicated its placement as a novel species within this genus. Digital DNA-DNA hybridization (dDDH) values and average nucleotide identity (ANI) analyses of this strain against closely related species confirmed its condition of novel taxon. On the other hand, the percentage of the average amino acid identity (AAI) affiliated strain 71-i T within the genus Marinobacter . The DNA G+C content of this isolate was 57.7 mol%. The major fatty acids were C 16 : 0 and C 16 : 1 ω 7c and/or C 16 : 1  ω6 c . Ubiquinone-9 was the major isoprenoid quinone and diphosphatidylglycerol (DPG), phosphatidylglycerol (PG) and phosphatidylethanolamine (PE) were the main polar lipids of this strain. On the basis of the phylogenomic and phenotypic (including chemotaxonomic) features, we propose strain 71-i T (= IBRC M 11023 T = CECT 30160 T = LMG 29252 T ) as the type strain of a novel species within the genus Marinobacter , with the name Marinobacter iranensis sp. nov. Genomic detections of this strain in various metagenomic databases indicate that it is a relatively abundant species in environments with low salinities (approximately 5 % salinity), but not in hypersaline habitats with high salt concentrations.

Filamentous green algae play an important functional role in element cycling and productivity in the different water bodies. In hypersaline lakes and lagoons of the Crimea, filamentous green algae are present and form bottom and floating mats that occupy large areas with high biomass, up to 4–5 kg (wet biomass)/m2. Cladophora spp. dominated in those mats. Five species of filamentous green algae (Chlorophyta) in Lake Chersonesskoye: Cladophora vadorum (Aresch.) Kütz., C. siwaschensisC. Meyer, C. echinus (Biasol.) Kütz., Ulothrix implexa (Kütz.) Kütz., Rhizoclonium tortuosum (Dillw.) Kütz., and seagrass (Angiospermae) Ruppia cirrhosa (Petagna) Grande were found. Cladophora spp. and R. cirrhosa were found in the lake throughout the year, other types of algae were encountered episodically. In most cases the biomass of bottom mat exceeded that of the floating mat. In general, the total biomass of the bottom and floating mats in the lake areas at depths up to 30 cm was in a stable range of values from 100 to 290 mg (dry weight)/cm 2. Animal and infusorian average abundance in mats reach high values: infusorians—up to 15 000 000 ind./m2, Cletocamptus retrogressus (Copepoda, Harpacticoida)—up to 730 000 ind./m2, Eucypris mareotica (Ostracoda)—up to 91 000 ind./m2 and Chironomidae larvae (Insecta, Diptera)—up to 140 ind./m2. Those values were much higher than in the plankton. [ABSTRACT FROM AUTHOR]

The screening of bacteria and archaea from Chott El Jerid, a hypersaline lake in the south of Tunisia, led to the isolation of 68 extremely halophilic prokaryotes growing in media with 15-25% of salt. Assessment of 68 partial 16S rRNA analyzed by amplified rDNA restriction analysis (ARDRA) revealed 15 different bacterial and archaeal taxonomic groups. Based on ARDRA results, phenotypic and hydrolytic activity tests, 20 archaeal and 6 bacterial isolates were selected for sequencing. The halophilic isolates were identified as members of the genera: Salicola, Bacillus, Halorubrum, Natrinema and Haloterrigena. Most of these isolates are able to produce hydrolytic enzymes such as amylase, protease, lipase, cellulase, xylanase, pectinase and some of them showed combined activities. Natrinema genus is an excellent candidate for lipase production. These results indicated that the extremely halophilic archaea and bacteria from Chott El Jerid are a potential source of hydrolytic enzymes and may possess commercial value. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The shift of the dominating complexes occurred in the bottom communities of the hyperhaline lake Manych-Gudilo. From August 2008 to February 2011 larvae of water predatory beetles predominated. Larvae of chironomids of the genus Baeotendipes Kieffer, 1913, which in 2007 and 2008 constituted up to 70% of the total biomass at coastal stations, in 2009 and 2010 were absent in samples. This change in the bottom communities’ structure is a result of influence of both biotic (elimination by predators) and abiotic factors (increasing of mineralization and growth of areas contaminated by hydrogen sulfide). Nevertheless, in April 2011 solitary specimens of chironomids were recorded again at coastal stations; their biomass fluctuated from 0.001 to 0.2 g/m2. By July, they were found along the whole area of the lake, but their quantitative characters remained low (from 0.02 to 0.4 g/m2). In spring and early summer 2012, larvae of Baeotendipes dominated at all stations by quantity and biomass.

The genus Salinivibrio belongs to the family Vibrionaceae and includes Gram-stain-negative, motile by a polar flagellum, and facultatively anaerobic curved rods. They are halophilic bacteria commonly found in hypersaline aquatic habitats and salted foods. This genus includes five species and two subspecies. A presumed novel species, strain S35T, was previously isolated from the high-altitude volcanic, alkaline, and saline lake Socompa (Argentinean Andes). In this study we carried out a complete taxonomic characterization of strain S35T, including the 16S rRNA gene sequence and core-genome analysis, the average nucleotide identity (ANIb, ANIm, and orthoANI), and in silico DNA−DNA hybridization (GGDC), as well as the phenotypic and chemotaxonomic characterization. It grew at 3%−20% (w/v) NaCl, pH 6−10, and 10−42 °C, with optimum growth at 7.0%−7.5% (w/v) NaCl, pH 8.0, and 37 °C, respectively. Strain S35T was oxidase- and catalase-positive, able to produce acid from D-glucose and other carbohydrates. Hydrolysis of DNA, methyl red test, and nitrate and nitrite reduction were positive. Its main fatty acids were C16:0, C16:1 ω7c and C16:1 ω6c, and C18:1 ω7c and/or C18:1 ω6c. ANI, GGDC, and core-genome analysis determined that strain S35T constitutes a novel species of the genus Salinivibrio, for which the name Salinivibrio socompensis sp. nov. is proposed. The type strain is S35T (= CECT 9634T = BNM 0535T).

Sulfur (S) plays a significant role in saline environments, and sulfate (SO 4 2 − ) is an important component of the biogeochemical S-cycle since it acts as the main electron acceptor in anoxic sediments. The purpose of this paper is to evaluate the fate of S, its origin, and processes affecting sulfate outcome in the hypersaline Pétrola Lake in the Castilla-La Mancha region (High Segura Basin, SE Spain). The lake is the terminal discharge zone of an endorheic basin with considerable anthropogenic pressures. Anthropogenic activities (mainly agricultural inputs and wastewater discharge), together with bedrock leaching of sulfate and sulfide-rich sediments, increase dissolved SO 4 2 − in surface and groundwater up to 123,000 mg/L. The source and fate of sulfate in this environment was investigated coupling hydrochemistry, including hydrogen sulfide (H 2 S) microprofiles, isotopic analyses (δ 34 S, δ 18 O SO4 , δ 2 H H2O , δ 18 O H2O , and tritium), mineralogical determinations, and molecular biology tools (16S rDNA amplification and sequencing). The origin of dissolved SO 4 2 − in water is related to pyrite oxidation from Lower Cretaceous sediments, and secondary gypsum dissolution. Under the lake, dissolved SO 4 2 − decreases with depth, controlled by three main processes: (1) seasonal evaporation cycles, (2) hydrodynamic instability caused by the different density-driven groundwater flow, and (3) sulfate-reduction processes, i.e. dissimilatory bacterial sulfate reduction (BSR). These processes control the continuous recycling of sulfur in the system. Lake water and groundwater are in hydraulic connection, and a density-driven flow (DDF) is able to transport reactive organic matter and dissolved SO 4 2 − towards the underlying aquifer. Hydrochemical evolution in depth, H 2 S production (up to 0.024 nmol/cm 3 ·s) and the presence of sulfate-reducing bacteria suggest the existence of BSR processes. However, isotope techniques are insufficient to elucidate BSR processes since their isotopic effect is masked by low isotope fractionation and high SO 4 2 − concentrations. The pattern here described may be found in other saline basins worldwide. [ABSTRACT FROM AUTHOR]

Artemia it is widely used as a launching feedstuff for the cultivation of fish larvae and Crustaceans. We studied the biochemical composition of cysts from different hyperhaline [do mean hypersaline] reservoirs, small lakes (Dushnoe, Malinovoe) as well as in the large Bolshoe and Maloe Jarovoe lakes, Kulundinsky, district located in the territory of Western Siberia in the Altai region. The relative quantitative analysis of interchangeable and essential amino acids, fatty acid contents, mineral substances and vitamins was carried out. Nonessential amino acids were dominant in most of the cysts from lake Maloe Jarovoe and Dushnoe. In lake Dushnoe, Bolshoe Jarovoe and Kulundinsky, lysine was the dominant amino acid.The dimension of lakes and their salinity authentically did not influence the composition of amino acids in the cysts. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

ABSTRACT Lake Urmia in northwestern corner of Iran was once the second largest hypersaline lake of the world, covering on average an area of 5200 km2. However, the lake has been shrinking rapidly over the last 20 years, primarily due to anthropogenic influences, while climate change has had also a detectable influence. Climate change and anthropohenic impacts on the rapid shrinkage of Lake Urmia are investigated using long-term surface meteorological records of weather stations, while the number of constructed dams and expansion of irrigated areas in the Urmia Basin are also examined. Over the past few decades, a warming trend of the order 0.18 °C decade−1 has been identified, while precipitation has been decreasing by approximately 9 mm decade−1 over the basin. As a consequence of such significant warming, evaporation from the lake has been increasing by the rate of 6.2 mm decade−1. The increased air temperature and evaporation, along with the decreased precipitation indicate that Lake Urmia has been experiencing meteorological drought conditions. The main anthropogenic influence, on the other hand, has been overwhelming diversion of water sources for irrigation, which led to the socioeconomic drought of the region because demand for water has exceeded the supply. The meteorological drought, combined by the socioeconomic drought, have contributed to the significant shrinkage of Lake Urmia, started from the mid 1990s water level peak, although the latter has had the most significant contribution. As a consequence, the water level of Lake Urmia has been rapidly declining since 1995, with 6.1 m decline for the period 1995-2009. Its surface area has been also changing by the rate of −188.3 km2 yr−1, reaching from 5503 km2 in 1998 to 2323 km2 in 2011. Under the induced meteorological and, more importantly, socioeconomic drought conditions, substantial improvements in water management practices are required to preserve or partially restore the lake. [ABSTRACT FROM AUTHOR]

Urmia Lake, the world's second largest hypersaline lake, has decreased in size over recent decades primarily because inflow has diminished. This has caused serious socio-environmental consequences similar to those of the Aral Sea disaster. By using the variable infiltration capacity (VIC) model, this study estimates the relative contributions of climate change and water resources development, which includes the construction of reservoirs and expansion of irrigated areas, to changes in Urmia Lake inflow over the period 1960–2010. The model results show that decreases in inflow generally follow observed decreases in precipitation, although the variability in inflow is more pronounced than the variability in precipitation. The results also suggest that water use for irrigation has increased pressure on the basin's water availability and has caused flows to decrease by as much as 40% during dry years. On the other hand, the presence of reservoirs positively contributed to water availability during relatively dry years and did not significantly reduce lake inflow. By accelerating irrigation expansion in the basin, reservoirs have, however indirectly, contributed to inflow reduction. Our results show that annual inflow to Urmia Lake has dropped by 48% over the study period. About three fifths of this change was caused by climate change and about two fifths was caused by water resource development. The results of this study show that, to prevent further desiccation of Urmia Lake, it will be necessary both to develop national plans to reduce irrigation water use and to develop international plans to address climate change. [ABSTRACT FROM AUTHOR]