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Over three-quarters of Earth's surface exhibits extreme environments where life thrives under harsh physicochemical conditions. While prokaryotes have often been investigated in these environments, only recent studies have revealed the remarkable adaptability of eukaryotes, in particular fungi. This study explored the mycobiota of two meromictic hypersaline lakes, Ursu and Fără Fund, in Transylvania (Romania). The intrinsic and extrinsic fungal diversity was assessed using amplicon sequencing of environmental DNA samples from sediments, water columns, surrounding soils, and an associated rivulet. The fungal communities, illustrated by the 18S rRNA gene and ITS2 region, exhibited contrasting patterns between the lakes. The ITS2 region assessed better than the 18S rRNA gene the fungal diversity. The ITS2 data showed that Ascomycota was the most abundant fungal group identified in both lakes, followed by Aphelidiomycota, Chytridiomycota, and Basidiomycota. Despite similar α-diversity levels, significant differences in fungal community structure were observed between the lakes, correlated with salinity, total organic carbon, total nitrogen, and ammonium. Taxonomic profiling revealed depth-specific variations, with Saccharomycetes prevalent in Ursu Lake's deeper layers and Lecanoromycetes prevalent in the Fără Fund Lake. The functional annotation using FungalTraits revealed diverse ecological roles within the fungal communities. Lichenized fungi were dominant in Fără Fund Lake, while saprotrophs were abundant in Ursu Lake. Additionally, wood and soil saprotrophs, along with plant pathogens, were more prevalent in the surrounding soils, rivulet, and surface water layers. A global overview of the trophic relations in each studied niche was impossible to establish due to the unconnected graphs corresponding to the trophic interactions of the analyzed fungi. Plotting the unweighted connected subgraphs at the genus level suggests that salinity made the studied niches similar for the identified taxa. This study shed light on the understudied fungal diversity, distribution, and ecological functions in hypersaline environments. [ABSTRACT FROM AUTHOR]

ABSTRACT Thick‐bedded halite sequences in the geological record are characterized by lateral variations, reflecting spatiotemporal variations in environmental forcing. Although temporal variations have been examined over seasonal scales or longer durations, there is a paucity of information regarding the dynamics of halite deposition at shorter durations of days and hours. Additionally, the influence of water discharges and surface salinity gradients remains poorly understood. Here, for the first time, in situ, hourly to weekly halite accumulation rates were measured on the Dead Sea floor (ca 20 m water depth), the only modern deep and hypersaline water body. Novel underwater photography methods were developed to directly observe halite precipitation at the lake floor, coeval with monitoring of the environmental drives, i.e. evaporation, meteorological and limnological conditions. Two fundamental environments were explored: a diluted plume environment arising from spring discharge; and a mixed hypersaline environment. The focus was on deposition during winter when the halite accumulation rate is highest, and the relationship between evaporation and halite accumulation is most straightforward since the water column is vertically uniform. Significant spatial variations in halite accumulation were found between the two environments, along with hourly variations in each environment. In the mixed hypersaline environment, over intra‐diurnal timescales, evaporation plays a more significant role in halite precipitation, whereas temperature has a greater impact on seasonal changes. In the diluted plume environment, the stability of the buoyant plume controls the rate of halite deposition; during windstorms, the plume is stirred, with higher surface water salinity and higher rate of halite accumulation. However, under calm winds, the plume is stable, with diluted surface water, and the rate of halite accumulation is a few times lower. Following these new findings, the implications for the interpretation of halite deposits are discussed. [ABSTRACT FROM AUTHOR]

Beta-mannans are insoluble plant polysaccharides with beta-1,4-linked mannose as the backbone. We used three forms of this polysaccharide, namely, pure mannan, glucomannan, and galactomannan, to enrich haloarchaea, which have the ability to utilize mannans for growth. Four mannan-utilizing strains obtained in pure cultures were closely related to each other on the level of the same species. Furthermore, another strain selected from the same habitats with a soluble beta-1,4-glucan (xyloglucan) was also able to grow with mannan. The phylogenomic analysis placed the isolates into a separate lineage of the new genus level within the family Natrialbaceae of the class Halobacteria. The strains are moderate alkaliphiles, extremely halophilic, and aerobic saccharolytics. In addition to the three beta-mannan forms, they can also grow with cellulose, xylan, and xyloglucan. Functional genome analysis of two representative strains demonstrated the presence of several genes coding for extracellular endo- beta-1,4-mannanase from the GH5_7 and 5_8 subfamilies and the GH26 family of glycosyl hydrolases. Furthermore, a large spectrum of genes encoding other glycoside hydrolases that were potentially involved in the hydrolysis of cellulose and xylan were also identified in the genomes. A comparative genomics analysis also showed the presence of similar endo-beta-1,4-mannanase homologs in the cellulotrophic genera Natronobiforma and Halococcoides. Based on the unique physiological properties and the results of phylogenomic analysis, the novel mannan-utilizing halolarchaea are proposed to be classified into a new genus and species Natronoglomus mannanivorans gen. nov., sp. nov. with the type strain AArc-m2/3/4 (=JCM 34861=UQM 41565). [ABSTRACT FROM AUTHOR]

Biosynthesis and biodegradation of microorganisms critically underpin the development of biotechnology, new drugs and therapies, and environmental remediation. However, most uncultured microbial species along with their metabolic capacities in extreme environments, remain obscured. Here we unravel the metabolic potential of microbial dark matters (MDMs) in four deep-inland hypersaline lakes in Xinjiang, China. Utilizing metagenomic binning, we uncovered a rich diversity of 3030 metagenome-assembled genomes (MAGs) across 82 phyla, revealing a substantial portion, 2363 MAGs, as previously unclassified at the genus level. These unknown MAGs displayed unique distribution patterns across different lakes, indicating a strong correlation with varied physicochemical conditions. Our analysis revealed an extensive array of 9635 biosynthesis gene clusters (BGCs), with a remarkable 9403 being novel, suggesting untapped biotechnological potential. Notably, some MAGs from potentially new phyla exhibited a high density of these BGCs. Beyond biosynthesis, our study also identified novel biodegradation pathways, including dehalogenation, anaerobic ammonium oxidation (Anammox), and degradation of polycyclic aromatic hydrocarbons (PAHs) and plastics, in previously unknown microbial clades. These findings significantly enrich our understanding of biosynthesis and biodegradation processes and open new avenues for biotechnological innovation, emphasizing the untapped potential of microbial diversity in hypersaline environments.

This research work proposes a novel method of environmental flow analysis in hypersaline lakes in which the outputs of the hydraulic rating method considering the base flow as a known approach for environmental flow assessment in rivers are analyzed in terms of providing suitable aquatic habitats in the lake by linking a continuous hydrological model and a hydrodynamic model of salinity simulation. Soil and Water Assessment Tool (SWAT) as a hydrological model was applied to simulate the natural inflow of the lake's ecosystem in the simulated period. Moreover, a hydrodynamic model was applied to simulate the salinity distribution of the lake in the same simulated period. Based on the results of the models and monthly analysis of the environmental flows, both models are robust for simulations. The Nash–Sutcliffe Efficiency (NSE) of both hydrological and hydrodynamic models average more than 0.5, which means that they are reliable for simulating the natural inflow and salinity distribution respectively. Furthermore, outputs indicated that using the hydraulic rating method considering the base flow for assessing the environmental flow of rivers is not able to provide environmental requirements in the lake's ecosystem of the case study. HIGHLIGHTS New method for environmental flow analysis.; Linking catchment model and hydrodynamic model.; Assessing environmental flow supply.;

Beta-mannans are insoluble plant polysaccharides with beta-1,4-linked mannose as the backbone. We used three forms of this polysaccharide, namely, pure mannan, glucomannan, and galactomannan, to enrich haloarchaea, which have the ability to utilize mannans for growth. Four mannan-utilizing strains obtained in pure cultures were closely related to each other on the level of the same species. Furthermore, another strain selected from the same habitats with a soluble beta-1,4-glucan (xyloglucan) was also able to grow with mannan. The phylogenomic analysis placed the isolates into a separate lineage of the new genus level within the family Natrialbaceae of the class Halobacteria. The strains are moderate alkaliphiles, extremely halophilic, and aerobic saccharolytics. In addition to the three beta-mannan forms, they can also grow with cellulose, xylan, and xyloglucan. Functional genome analysis of two representative strains demonstrated the presence of several genes coding for extracellular endo-beta-1,4-mannanase from the GH5_7 and 5_8 subfamilies and the GH26 family of glycosyl hydrolases. Furthermore, a large spectrum of genes encoding other glycoside hydrolases that were potentially involved in the hydrolysis of cellulose and xylan were also identified in the genomes. A comparative genomics analysis also showed the presence of similar endo-beta-1,4-mannanase homologs in the cellulotrophic genera Natronobiforma and Halococcoides. Based on the unique physiological properties and the results of phylogenomic analysis, the novel mannan-utilizing halolarchaea are proposed to be classified into a new genus and species Natronoglomus mannanivorans gen. nov., sp. nov. with the type strain AArc-m2/3/4 (=JCM 34861=UQM 41565).

Modern and ancient hypersaline brines have been identified across the solar system, but the habitability of these environments remains unknown. Here, we evaluate organic matter (OM) production in MgSO4 and Na2CO3 rich hypersaline lakes whose chemistries resemble deposits on Mars such as those identified in Jezero crater. We focus our analysis on lipid biomarkers including fatty acids, alkanes, and ether‐bound lipids in modern brines, salt deposits, and surface sediments. We also report total organic carbon (TOC), carbon/nitrogen (C/N) ratios, and bulk OC (δ13C and δ15N) isotopes to contextualize the lipid biomarker data. In all lakes, the predominant biosignatures include midchain (12 < C < 23) fatty acids and alkanes suggesting microbial origin. Sediments also incorporate a greater diversity of lipids. Ether‐bound lipids derived from archaea and bacteria constitute a minor but measurable fraction of the lipids. This result contrasts with typical findings from other studies with NaCl brines which contain significant archeal biomass. TOC concentrations in all sediments are high, ranging from 0.7% to 12% with sulfate‐rich sediments having the highest concentrations. The isotopic and elemental compositions of TOC corroborate the biomarker results, showing δ13C values and C/N values indicative of aquatic microbial origin. This richness of organic matter and in situ microbial biosignatures differ from previously studied Cl‐dominated Mars‐analog sites which have shown limited OM production and preservation and acidic SO4‐rich hypersaline environments which were dominated by terrestrial inputs. Overall, our results suggest that MgSO4‐rich hypersaline environments are conducive for life and harbor a rich microbial biomarker landscape. Plain Language Summary: The minerals found on Mars suggest that it had abundant hypersaline waters early in its history. However, liquid water no longer persists on its surface. As such, we must use environments on Earth that are similar to Mars and other astrobiological targets to better understand the potential for life elsewhere. Here, we examine fatty molecules and organic carbon from hypersaline lakes on Earth that resemble water compositions thought to have been present on early Mars. We also use bulk carbon isotopic data to help inform the results from our biomarker analysis. Overall, data from these sites shows that circumneutral SO4‐rich environments are conducive for life and harbor a suite of microbial biosignatures. In comparison to other Martian‐analog environments on Earth, this study shows that circumneutral SO4‐dominated lakes produce in situ biological signatures in abundance. Key Points: SO4‐dominated hypersaline lakes produce more abundant organic matter (OM) than a Na2CO3‐dominated site of comparable salinityThe circumneutral MgSO4‐dominated hypersaline lakes studied here harbor abundant microbial biosignatures compared to other Martian analogsLipid biosignatures produced in situ predominate within sedimentary OM rather than biosignatures produced by surrounding vegetation [ABSTRACT FROM AUTHOR]

The results of 2020 studies of bottom cysts of brine shrimp Artemia in Lake Kuchukskoe and Lake Bolshoe Yarovoe in Altai krai (Russia) are presented. Artemia cysts were observed year round at the bottom of both lakes. The number of cysts depended on the type of bottom sediment. The biomass of bottom cysts in Lake Kuchukskoe was 154.2 t in spring, of which available and visually intact cysts constituted from 11.8 to 25.2 t. Bottom cysts of Artemia were not available for 27% of the lake area in Lake Kuchukskoe due to the high salinity of the water and salt precipitation. The viability of cysts from shallow bottom areas was 8.9% in spring. In Lake Kuchukskoe, cysts from accumulations on the coast, washed away by the runoff of melt water, played the main role in the formation of first generation of Artemia in spring. The deep water of Lake Bolshoe Yarovoe predetermined the peculiarities of the temperature regime in spring, which prevented brine shrimp cysts from ascending from the bottom if the depth exceeded 7.0 m. Significant silt deposits at the bottom of the lake were an aggressive environment for cysts, as was followed by the presence of different groups of cyst quality: visually intact, with defective chorion, gray or black. The biomass of bottom cysts in Lake Bolshoe Yarovoe was 38 934 t in autumn 2020, which exceeded the reproductive capacity of the Artemia population per year. This testified to the long-term period of accumulations of cysts at the bottom and their partly participation in the formation of the Artemia first generation in spring. In spring, the maximum hatching rate of nauplii from bottom cysts was 16% from depths exceeding 9.0 m and 26%, from a depth of 8.0 m. The viability of bottom cysts from Lake Bolshoe Yarovoe does not exceed 15% at the average; unhatched floating cysts settle back to the bottom in summer. [ABSTRACT FROM AUTHOR]

Crimean salt lakes have a high resource potential used in various types of human activity, i.e., balneology, chemical industry, and therapy; now, they are attractive tourist sites. A combination of biotic and abiotic factors creates specific conditions for the development and functioning of biota and the formation of unique ionic composition of brine and bottom sediments, which are used in balneology and the production of spa-products. Sakskoe Lake is among the largest coastal salt lakes of Crimea, located on the southwestern coast of the Black Sea. The effect of climate conditions and biota caused the formation of a specific ecosystem in the lake, which has a peculiar ionic composition of brine, changing within the year, and a brine shrimp population. The concentrations of cations and anions in the brine increased in summer because of active evaporation and decreased in winter and spring because of dilution of atmospheric precipitation and snowmelt water. The dynamics of the brine population also showed characteristic seasonal features: the life cycle begins in April, the maximal number of various life stages is recorded in May–June, and the end, in November–December. The artificial regulation of the water–salt regime of the water body through addition of seawater in summer contributed to maintaining optimal conditions, thus ensuring a high vital activity of the biota. The obtained data can reflect the seasonal dynamics of processes in the salt lake, governed by climatic, seasonal, and anthropogenic factors. [ABSTRACT FROM AUTHOR]

Extremely halophilic archaea (haloarchaea) of the class Halobacteria is a dominant group of aerobic heterotrophic prokaryotic communities in salt-saturated habitats, such as salt lakes and solar salterns. Most of the pure cultures of haloarchaea were enriched, isolated, and cultivated on rich soluble substrates such as amino acids, peptides or simple sugars. So far, the evidences on the capability of haloarchaea to use different polysaccharides as growth substrates remained scarce. However, it is becoming increasingly obvious that these archaea can also actively participate in mineralization of complex biopolymers, in particular cellulose and chitin-two dominant biomass polysaccharides on the planet. Here we used an array of commercially available homo- and heteropolysaccharides to enrich hydrolytic haloarchaea from hypersaline salt lakes with neutral pH and from alkaline soda lakes. This resulted in isolation of a range of halo- and natronoarchaea, respectively, belonging to already described taxa as well as several new genus-level lineages. In some cases, the isolates enriched with different polysaccharides happened to be closely related, thus representing generalistic ecotype, while the others were narrow specialists. In general, soda lakes yielded a broader range of polysaccharide-utilizing specialists in comparison to neutral salt lakes. The results demonstrated a significant diversity of halo(natrono)archaea with a previously unrecognized potential for utilization of a broad range of natural polysaccharides in hypersaline habitats. [ABSTRACT FROM AUTHOR]

Field observations of the diurnal behavior of several parameters (oxygen concentration, chlorophyll fluorescence, photosynthetically active radiation (PAR), wind speed, temperature, suspended matter concentration, and zooplankton abundance) were conducted at three sites in the marine hypersaline lake Moynaki (Crimea). The diurnal course of PAR followed a bell-shaped form, with the maximum at 14:00 on the 15th and 16th of September 2021. The oxygen concentration varied over a wide range from 3.2 to 9.3 mg L−1, demonstrating a clear diurnal rhythm. From sunrise until about 17:30, it increased. Both the maximum and minimum values were marked on the site where there were Ruppia thickets. The daily rhythm of Chlorophyll a concentration was clearly expressed during the observation period, varying from 2.49 to 18.65 µg L−1. A gradual increase in the concentration of chlorophyll a began after 10:00 and lasted until about 2:30–3:00 of the next day. The daily production of oxygen during photosynthesis averaged 27.3 mgO L−1 day−1, and the highest values were noted at the windward site of 37.9 mgO L−1 day−1, and the lowest at the leeward site of 19 mgO L−1 day−1. The total respiration of the community per day was, on average, 15.9 mgO L−1 day−1. It averaged 63% of the primary production created. The contribution of animals to the total oxygen consumption of the community was small, averaging 5%. [ABSTRACT FROM AUTHOR]

The present study proposes an applicable methodology to optimize environmental water requirement of hypersaline lakes with a focus on Urmia lake as the case study in which remote sensing analysis, machine learning model and fuzzy expert system are linked. A machine learning model was developed to simulate effective abiotic parameters in which bands of operational land imager (Landsat 8) were inputs and depth and total dissolved solids were the outputs of the model. Moreover, an ecological expert system using Mamadani fuzzy inference system was developed to generate the habitat suitability map for the selected target species. Then, a multivariate linear model was developed to assess unit habitat suitability in which water level and total inflow of the lake were the variables of the model. An optimization model was developed to assess environmental water requirement in which habitat suitability between natural and regulated flows and water supply loss was minimized. The multivariate linear model was applied to assess habitat suitability in the optimization model. Based on the results in the case study, the proposed combined model is able to balance the ecological requirements and water demand by allocating 60% and 40% of total inflow to environmental water requirement and water demand respectively. Average habitat loss proposed by the optimal environmental water requirement was less than 20% which implies the robustness of the model. Generating habitat suitability maps of the lake by a reliable method which is used in the environmental flow optimization might be the significance of the proposed method. [ABSTRACT FROM AUTHOR]

Many works have been devoted to the study of the molecular genetic diversity of Artemia in different regions; however, there are regions such as Crimea, the largest peninsula in the Black Sea, which has seen few studies. Artemia specimens from several Crimean hypersaline lakes were analyzed using the mitochondrial marker cytochrome oxidase C (COI). The analyzed individuals from bisexual populations formed clades with the species A. salina, A. urmiana, A. sinica, and A. monica (=A. franciscana). A. sinica and A. monica had not been recorded in Crimea previously. In Lake Adzhigol, the three species A. urmiana, A. sinica, and A. monica were found at the same time, which has not been noted anywhere before. In the Crimean lakes, a total of 10 haplotypes were found, six of them for the first time: Once for A. monica, once for A. sinica, and four for A. salina. Those haplotypes may be regarded as endemic to Crimea. In the 1990s, experiments were carried out in Lake Yanyshskoe using mainly purchased cysts of Artemia, so A. monica and A. sinica were introduced into Crimea and could then have easily been spread by birds to other Crimean lakes. [ABSTRACT FROM AUTHOR]

Unique lakes of various genesis are found on the Crimean Peninsula, which have a high recreational and balneological potential. They are under a significant anthropogenic load, which, along with the arid climate, leads to negative consequences for the ecosystems and even to the loss of biological and hydro-mineral resources. More than this, the closely located water bodies can differ significantly due to differences in human activities. Lake Moinaki on the western outskirts of Yevpatoria is divided by a sand barrier into two reservoirs, Moinaki-1 (larger) and Moinaki-2 (smaller). The aim of this work was to study some physicochemical parameters of water (temperature, pH, oxygen content, salinity, and redox potential, Еh) and Artemia population (Artemia salina (L, 1758)) in these water bodies in 2018–2020. The seasonal dynamics of the studied parameters has been characterized by an increase in salinity and Eh in summer resulted from an increase in air and water temperature and its intense evaporation. Simultaneously, a decrease in oxygen content and as well as in pH levels has been observed. The identified features were more pronounced in Moinaki-2 than in Moinaki-1. Artemia cysts were found in both reservoirs, while nauplii and adults were found only in Moinaki-2 in 2020, after drying and subsequent restoration of the hydrological regime of the water body. [ABSTRACT FROM AUTHOR]

Extremely halophilic archaea (haloarchaea) of the class Halobacteria is a dominant group of aerobic heterotrophic prokaryotic communities in salt-saturated habitats, such as salt lakes and solar salterns. Most of the pure cultures of haloarchaea were enriched, isolated, and cultivated on rich soluble substrates such as amino acids, peptides or simple sugars. So far, the evidences on the capability of haloarchaea to use different polysaccharides as growth substrates remained scarce. However, it is becoming increasingly obvious that these archaea can also actively participate in mineralization of complex biopolymers, in particular cellulose and chitin–two dominant biomass polysaccharides on the planet. Here we used an array of commercially available homo- and heteropolysaccharides to enrich hydrolytic haloarchaea from hypersaline salt lakes with neutral pH and from alkaline soda lakes. This resulted in isolation of a range of halo- and natrono-archaea, respectively, belonging to already described taxa as well as several new genus-level lineages. In some cases, the isolates enriched with different polysaccharides happened to be closely related, thus representing generalistic ecotype, while the others were narrow specialists. In general, soda lakes yielded a broader range of polysaccharide-utilizing specialists in comparison to neutral salt lakes. The results demonstrated a significant diversity of halo(natrono)archaea with a previously unrecognized potential for utilization of a broad range of natural polysaccharides in hypersaline habitats.

In La Pampa province, limnological studies have been carried out in saline lakes, generally located in basins with agricultural exploitations. In Parque Luro Provincial Reserve there are two scarcely studied saline lakes: East and West Lakes. The objective was to analyze physical-chemical parameters and those of the plankton of these protected environments and compare them with other Pampean lakes under different anthropic influence. Monthly samples were collected between October 2014 and September 2015. In both lakes, Cl- and Na+ predominated, but salinity differed (East: 276.53 ±42.00 g.L-1, West 29.33 ±10.25 g.L-1). West Lake was covered by the macrophyte Ruppia cirrhosa and water was transparent. Accumulated phytoplankton richness was 30 taxa, and was negatively influenced by salinity, since the highest richness (22 taxa) was that of West Lake. In both lakes the most frequent species were Dunaliella salina and D. viridis. Fourteen taxa were found in zooplankton of both lakes, and richness was also influenced by salinity. In East Lake only Artemia persimilis was recorded and in West Lake the typical association of mesosaline Central Argentine lakes was recorded, in low density due to the dense coverage of the macrophyte. [ABSTRACT FROM AUTHOR]

Migration of nutrients is studied in five drying salt lakes belonging to the Yevpatoriya Group (Crimea). The nutrients enter in the Crimean salt lakes from natural sources, in particular, atmospheric precipitation, erosion materials, seawater overflow during storms, products of vital activity of birds and animals grazing on coasts, processes in ecosystems (eutrophication and vital functions of aquatic organisms). Nitrogen and phosphorus are also supplied with runoff directly in water bodies and indirectly via ground waters, and recreation activity on the lake coasts. An increase of air temperature above +30°C in summer caused intense evaporation and drying up of the lakes. In drying water bodies, the natural processes of the nitrogen and phosphorus migration are terminated due to cessation of biota functioning, especially of microalgae, microbial communities and crustacean Artemia. In drying periods, nitrogen, phosphorus, and pollutants are accumulated and concentrated on the bottom sediments and during strong storms and winds are propagated over adjacent territory and, respectively, represent a threat to human health. The paper discusses the possible scenario of the transformation of ecosystems of saline lakes under possible climatic warming and increasing anthropogenic impact. [ABSTRACT FROM AUTHOR]

The wetlands and salt flats of the Central Andes region are unique extreme environments as they are located in high-altitude saline deserts, largely influenced by volcanic activity. Environmental factors, such as ultraviolet (UV) radiation, arsenic content, high salinity, low dissolved oxygen content, extreme daily temperature fluctuation, and oligotrophic conditions, resemble the early Earth and potentially extraterrestrial conditions. The discovery of modern microbialites and microbial mats in the Central Andes during the past decade has increased the interest in this area as an early Earth analog. In this work, we review the current state of knowledge of Central Andes region environments found within lakes, small ponds or puquios, and salt flats of Argentina, Chile, and Bolivia, many of them harboring a diverse range of microbial communities that we have termed Andean Microbial Ecosystems (AMEs). We have integrated the data recovered from all the known AMEs and compared their biogeochemistry and microbial diversity to achieve a better understanding of them and, consequently, facilitate their protection. [ABSTRACT FROM AUTHOR]

This study was carried out in two hypersaline lakes (Acı and Meke Lakes) in Turkey to understand the diversity and geographic distribution of free-living heterotrophic flagellates. Heterotrophic flagellates of hypersaline environments have not previously been studied in Turkey. We found seventeen morphospecies of heterotrophic flagellates with one unidentified protist. The observed species belong to Craspedida, Heterolobosea, Apusomonadida, Neobodonida, Bicosoecida and Protista incertae sedis. Of the 17 species, ten species were new records for Turkey. All of the morphospecies described here except one unidentified protist were previously reported elsewhere and appear to be cosmopolitan. [ABSTRACT FROM AUTHOR]

Great Salt Lake (GSL) is a critical staging area for 2 species of phalaropes: Wilson's (Phalaropus tricolor) and Red-necked (P. lobatus). Both rely on the abundant invertebrate prey at GSL to fuel their fall migrations to Central and South America, but little is known about where phalaropes forage on GSL, what foraging methods are used, or what variables influence their foraging decisions. During 2014 and 2015, the frequency of specific foraging behaviors by phalaropes differed by GSL bays; surface picking was the most common foraging behavior (≥50%) on Carrington and Gilbert bays while spinning was the most common on Farmington Bay. Most (60%) Red-necked Phalaropes used surface picking for foraging compared to 32% of Wilson's Phalaropes. Spinning behavior to upwell prey was more common in Wilson's Phalaropes (used by 19% of foraging birds) than Red-necked Phalaropes (3%). The proportion of phalaropes in a flock that were foraging was positively associated with biomass of invertebrate prey at the flock's location. Most (64%) of the phalarope flocks were on Farmington Bay, and 75% of phalaropes in this bay were foraging, compared to 41% of birds on Gilbert Bay. Thus, Farmington Bay is particularly important for hundreds of thousands of Red-necked and Wilson's phalaropes that stage on GSL for 4 months during each summer. Farmington Bay is brackish, shallow, and depends on the Jordan River for its freshwater. The future of this water source, and therefore Farmington Bay itself, is uncertain because of future diversions by humans and longer droughts predicted from climate change. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Field observations of the diurnal behavior of several parameters (oxygen concentration, chlorophyll fluorescence, photosynthetically active radiation (PAR), wind speed, temperature, suspended matter concentration, and zooplankton abundance) were conducted at three sites in the marine hypersaline lake Moynaki (Crimea). The diurnal course of PAR followed a bell-shaped form, with the maximum at 14:00 on the 15th and 16th of September 2021. The oxygen concentration varied over a wide range from 3.2 to 9.3 mg L−1, demonstrating a clear diurnal rhythm. From sunrise until about 17:30, it increased. Both the maximum and minimum values were marked on the site where there were Ruppia thickets. The daily rhythm of Chlorophyll a concentration was clearly expressed during the observation period, varying from 2.49 to 18.65 µg L−1. A gradual increase in the concentration of chlorophyll a began after 10:00 and lasted until about 2:30–3:00 of the next day. The daily production of oxygen during photosynthesis averaged 27.3 mgO L−1 day−1, and the highest values were noted at the windward site of 37.9 mgO L−1 day−1, and the lowest at the leeward site of 19 mgO L−1 day−1. The total respiration of the community per day was, on average, 15.9 mgO L−1 day−1. It averaged 63% of the primary production created. The contribution of animals to the total oxygen consumption of the community was small, averaging 5%.

• A numerical model is developed based on FVCOM and PHREEQC for hypersaline lakes. • The model is used to study hydrodynamics and salinity regime in Lake Urmia. • Results by the developed model agree with the in-situ data. • Precipitation & dissolution contribute significantly to the lake salinity balance. • The model is useful for policymakers to develop more effective restoration plans. Due to anthropogenic activities and climate change, Lake Urmia, one of the largest hypersaline lakes, is exposed to desiccating condition. The increase in salinity in this lake to more than 400 PSU has endangered its ecosystem. Therefore, all restoration efforts have focused on restoring Lake Urmia by raising its water level to 1274.1 m above the see level to reduce lake salinity below 240 g/L NaCl. However, salinization processes in the lake have not been well-explored yet. To fill this gap, we extended a three-dimensional Finite Volume Community Ocean Model (FVCOM) to take account of the salt exchange between the lakebed and the water column. Precipitation and dissolution rates of mineral species were obtained by utilizing the PHREEQC inverse modeling. The model was calibrated using in situ salinity, water temperature, water level and velocity field data, and then was used to investigate hydrodynamics and salinity transport processes in the lake. Results indicate that by ignoring the surface heat flux, the model error in salinity prediction increases more than 1.8 times, which shows the importance of the effect of water temperature on the salinity distribution. This study also highlights the major contributions of salt precipitation and dissolution to the salinity balance of Lake Urmia to the extent that the simulated lake salinity is predicted to be 38% lower on average than the observed salinity by neglecting the salt exchange between the lakebed and the water column. The model presented in this study provides a better understanding of hydrodynamics and salinity patterns in hypersaline lakes and would be of use to stakeholders and managers to develop more effective lake restoration plans. [Display omitted] [ABSTRACT FROM AUTHOR]

Many works have been devoted to the study of the molecular genetic diversity of Artemia in different regions; however, there are regions such as Crimea, the largest peninsula in the Black Sea, which has seen few studies. Artemia specimens from several Crimean hypersaline lakes were analyzed using the mitochondrial marker cytochrome oxidase C (COI). The analyzed individuals from bisexual populations formed clades with the species A. salina, A. urmiana, A. sinica, and A. monica (=A. franciscana). A. sinica and A. monica had not been recorded in Crimea previously. In Lake Adzhigol, the three species A. urmiana, A. sinica, and A. monica were found at the same time, which has not been noted anywhere before. In the Crimean lakes, a total of 10 haplotypes were found, six of them for the first time: Once for A. monica, once for A. sinica, and four for A. salina. Those haplotypes may be regarded as endemic to Crimea. In the 1990s, experiments were carried out in Lake Yanyshskoe using mainly purchased cysts of Artemia, so A. monica and A. sinica were introduced into Crimea and could then have easily been spread by birds to other Crimean lakes.

Halite sequences in the geological record accumulated in deep hypersaline basins. However, such halite sequences are interpreted based on modern analogues of halite deposition in shallow hypersaline environments. Recently, halite deposition in the deep, hypersaline Dead Sea has been studied together with its coeval environmental and limnogeological forcing. This is the closest modern analogue for deep environments. Therefore, stratigraphy, sedimentology and petrography of a well‐dated, high‐resolution modern Dead Sea halite sequence are explored. The sequence was deposited during a ca 30 m lake‐level decline since the onset of modern halite deposition in 1980, and was compared with sub‐annual lake levels, precipitation and flood records. The sedimentology of the sequence documents the trend of shallowing water depth, including individual floods. The sequence base is composed of alternating bottom growth‐cumulate halite annual couplets, typical of deep hypolimnetic water deposition. Up‐sequence, the annual couplets disappear and towards its top are composed of cumulate layers with dissolution features, typical of shallow epilimnetic water deposition. Halite deposition rate is reduced by 60% at the shallow lakefloor compared with the deep lakefloor, mainly due to the summer undersaturation that leads to depocentre 'halite focusing'. The top of the sequence contains shoreline deposits, halolites (halite ooids) and polygonal surface cracks, indicating subaerial exposure. This study shows petrographic indicators for summer thermal dissolution (partially dissolved crystals), which are distinct from dissolution features by winter floods that generate a regional truncation surface. Spatial variations in halite thickness and facies, indicating much thinner and spatially limited halite units compared to modelled halite units based on mass balance considerations were also observed. These observations provide criteria for: (i) recognizing water depths and shallowing lake‐level trends from halite sequences throughout the geological record; and (ii) interpreting palaeolimnology, water column structure and the relations between stratigraphic horizons and corresponding shorelines. [ABSTRACT FROM AUTHOR]

Dimethylsulfoxide (DMSO) has long been known to support anaerobic respiration in a few species of basically aerobic extremely halophilic euryarchaea living in hypersaline lakes. Recently, it has also been shown to be utilized as an additional electron acceptor in basically anaerobic sulfur-reducing haloarchaea. Here we investigated whether haloarchaea would be capable of anaerobic respiration with other two sulfoxides, methionine sulfoxide (MSO) and tetramethylene sulfoxide (TMSO). For this, anaerobic enrichment cultures were inoculated with sediments from hypersaline salt and soda lakes in southwestern Siberia and southern Russia. Positive enrichments were obtained for both MSO and TMSO with yeast extract but not with formate or acetate as the electron donor. Two pure cultures obtained from salt lakes, either with MSO or TMSO, were obligate anaerobes closely related to sulfur-reducing Halanaeroarchaeum sulfurireducens, although the type strain of this genus was unable to utilize any sulfoxides. Two pure cultures isolated from soda lakes were facultatively anaerobic alkaliphilic haloarchaea using O2, sulfur and sulfoxides as the electron acceptors. One isolate was identical to the previously described sulfur-reducing Natrarchaeobaculum sulfurireducens, while another one, enriched at lower alkalinity, is forming a new species in the genus Halobiforma. Since all isolates enriched with either MSO or TMSO were able to respire all three sulfoxides including DMSO and the corresponding activities were cross-induced, it suggest that a single enzyme of the DMSO-reductase family with a broad substrate specificity is responsible for various sulfoxide-dependent respiration in haloarchaea. [ABSTRACT FROM AUTHOR]

Atanasovsko Lake is a coastal lagoon used for salt extraction for many years. Its salinity varies within a wide range (from 6.3 to > 72‰). Despite these extreme conditions, phytoplankton blooms are often observed. Therefore, our aim was to study the key abiotic drivers and ecological optimum of the picoplankton in a 5-year period (2013-2017). The taxonomic composition, long-term dynamics and abiotic drivers of the autotrophic picoplankton (APP) has been investigated in North Saltern of the coastal lagoon in Atanasovsko Lake. The APP species were identified by using a polyphasic approach based on molecular and phylogenetic analyses of 16S/18S rDNA in combination with cytomorphological and ecological characterization. Picochlorum oklahomense (Trebouxiophyceae, Chlorophyta) and marine Synechococcus sp. (Synechococcales, Cyanobacteria) were the dominant genotypes within the APP. The relative biovolume of the APP to the total phytoplankton biovolume was strongly variable (from 36 to 99%) as the salinity and temperature were found to be the main abiotic drivers of its dynamics. Salinity between 30-59‰ and mid-summer temperature above 24°С provide an ecological optimum for the APP development at a relative biovolume of 93%. This is the first record of Picochlorum оklahomense/Synechococcus sp. assemblage within the APP composition of a European coastal lagoon. [ABSTRACT FROM AUTHOR]

Nitrogen (N) is often a limiting nutrient in lacustrine systems, and bulk organic matter stable isotope ratios of N (δ15N) are widely used in lake sediment studies to interpret N source inputs and lake trophic status. Although records of lacustrine sedimentary δ15N can provide critical information relating to past environmental change, often productivity interpretations from δ15N and lacustrine fossil records yield conflicting interpretations. Furthermore, components of the internal N cycle have substantial isotopic fractionation factors, and likely wield an enormous influence on bulk lacustrine sedimentary δ15N values. Yet apart from cyanobacteria N-fixation, few studies link specific microbial, N-related activity to δ15N variability in lake sediment records. Here, we assess the relationship between lacustrine sedimentary δ15N and microbiome profiles analyzed from extracted sediment DNA using metagenomics. In a ~ 1600-year-long sediment record from a hypersaline lake located on Kiritimati, Republic of Kiribati (1.9° N, 157.4° W), both δ15N and the taxonomy annotations from five unique metagenomes vary with depth. Despite the relatively high abundance of Cyanobacteria, Bacteroidetes, and N-fixation genes in the uppermost sediment, we find the highest δ15N values of the sediment record there. These high values are likely due to denitrification, supported by a relatively high abundance of denitrification genes and taxa responsible for denitrification, such as those found in family Chromatiaceae within the Gamma-proteobacteria. In the deep sediment, N-related biochemical processes are likely suppressed considering the low energy, low nutrient subsurface environment. Low δ15N values observed in deeper sediments co-occur with genes for assimilatory nitrate reduction and ammonification. Thus, metagenomics provides greater clarity with respect to the specific, microbial processes that alter primary δ15N signatures in the subsurface sediment. [ABSTRACT FROM AUTHOR]

Surface waters from hypersaline lakes of Cojocna Balneary Resort, Transylvania, Romania have been investigated in raw form, using Raman spectroscopy techniques. These lakes are usually exposed to high touristic influx mainly in summer months, due to their balneotherapeutic benefits. Therefore, chemical composition of waters and its variability is of high interest. Here we present spectroscopic characteristics of the lakes, obtained by Raman scattering techniques, probing several water samples collected in two consecutive years. Among the two lakes, Torok Lake showed 1.449 times higher sulfate concentration than the Great Lake in 2016 and 0.737 in 2017 respectively, according to the calculated ratio of the Raman band of sulfate at 979 cm-1 relative to water band. Chemical changes associated with the presence of different plankton species and their density fluctuations were reflected in changes in resonance Raman scattering signal of carotenoids during Artemia salina crustaceans blooming population in August, compared to July, in both years. Interestingly, the bloom appeared alternatively in two consecutive years and it is apparently correlated to lower sulfate level, as revealed by spectral data only. Raman data indicated the dynamic cycles in chemical composition of salt lakes. Such changes are certainly suitable for constant monitoring purpose of the balneotherapeutic salt water bodies via Raman spectroscopy. Both FT-Raman and dispersive Raman are suitable for this purpose. Fast analysis, without additional separation steps and chemicals consumption may provide information on the sulfate level and carotenoids. The results could be attractive for monitoring studies, or informative, for touristic purpose or aquaria hobby cultivars.

Fibrous‐radiating carbonate spherulites spatially associated with poorly crystalline Mg‐Si substances have formed within conical microbialites in modern hypersaline lakes on Rottnest Island, Western Australia. Two spherulitic fabrics can be distinguished based on compositional and textural differences. The oldest (lowermost) fabric comprises variably intergrown aragonitic spherulites 100–500 μm wide, containing micritic nuclei with coccoid cell molds in various stages of cell division. Spherulite matrices contain aggregates of individual nanospheres 150–200 nm wide, composed of a poorly crystalline Mg‐Si phase, locally containing cell molds with similar dimensions to those within spherulite nuclei. The younger (upper) fabric comprises sub‐polyhedral networks of mineralized EPS composed of an Mg‐Si substance. The polyhedrons contain aragonite‐replaced coccoid cells, voids, and polyhedral spherulites 8–12 μm wide with a morphology determined by fossil EPS, interpreted to have been produced by coccoid cyanobacteria. These spherulites are composed of high‐Mg calcite, inferred to have formed in association with heterotrophic bacteria. Stable isotope data, textural relationships, and geochemical modeling are consistent with cyanobacterial oxygenic photosynthesis influencing the precipitation of Mg‐Si substances and aragonitic spherulites by locally increasing the pH. The morphology of the polyhedral spherulites suggests the former presence of EPS and that faceted spherulites with similar dimensions in the geological record may represent biosignatures. The Rottnest Island conical microbialites demonstrate an intimate association between microbial features and processes and spherulitic fabrics, potentially providing insights into texturally and compositionally similar features in the geological record. [ABSTRACT FROM AUTHOR]

The paper presents data on seasonal fluctuations in hydrochemical characteristics and the supply dynamics of biogenic elements in four hypersaline lakes in Crimea: Sasyk-Sivash, Oiburg, Konrad, and Sakskoe (eastern basin) in 2017. The migration pathways of biogenic elements in the hypersaline lakes are determined depending of natural and anthropogenic factors. The role of the elements in ecosystem processes, the formation of peloids, and the functioning of communities of organisms are discussed. Probable transformation scenarios of the ecosystems of saline lakes are considered as a function of climatic changes, increasing anthropogenic load, and related increase in the inflow of biogenic elements. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Microbialites are organo-sedimentary structures formed as minerals precipitate due to the metabolic activity of microorganisms. They can be differentiated by their internal mesostructure into stromatolites and thrombolites. Lake Sarmiento, located in the Patagonia region of southern Chile, is a sub-saline alkaline lake in which living submerged and sub-fossil thrombolites are present. A submerged thrombolite was collected and one of the fragments was deposited in an experimental aquarium for 1.5 years, in order to examine possible changes to its biological and chemical composition. The bacterial biodiversity was examined using Illumina sequencing of PCR-amplified 16S V4 rRNA genes from total extracted DNA. The chemical structure was studied using XRD and bench chemical methods. The results show that in the living submerged and aquarium thrombolite samples, the Proteobacteria, Verrucomicrobia, Planctomycetes and Bacteroidetes phyla dominated the bacterial communities, which were similar at the upper taxonomic level. However, differences between the samples were detected at deeper classification levels (class, genus). Interestingly, no changes in the carbonate composition of the thrombolites were observed after culturing during 1.5 years. This study is the first to provide new insights into the bacterial community composition of thrombolites from this site. The thrombolites from Lake Sarmiento are active and contain a unique bacterial community composition. Further studies, including greater sampling and greater variety of experimental conditions in vitro (aquarium) will be helpful to create a global understanding of the microbial composition and formation of the thrombolites from Lake Sarmiento. [ABSTRACT FROM AUTHOR]

Summarizing authors’ own results and literature data, a brief overview of the Cyclopoida species in hypersaline waters of the Crimea and the world was done. In total, 28 species of cyclops in these extreme conditions were found. Twice representatives of these copepods were observed at salinity up to 300 g/L. The frequency of cyclops occurrence depends on salinity. It was found that the salinity up to 120-150 g/L is not the main factor affecting the presence and abundance of cyclops in water bodies, the more important factors – the level of phytoplankton development and the concentration of osmolytes in its biomass

The genomes of Thiohalobacter thiocyanaticus and Guyparkeria (formerly known as Halothiobacillus) sp. SCN-R1, two gammaproteobacterial halophilic sulfur-oxidizing bacteria (SOB) capable of thiocyanate oxidation via the “cyanate pathway”, have been analyzed with a particular focus on their thiocyanate-oxidizing potential and sulfur oxidation pathways. Both genomes encode homologs of the enzyme thiocyanate dehydrogenase (TcDH) that oxidizes thiocyanate via the “cyanate pathway” in members of the haloalkaliphilic SOB of the genus Thioalkalivibrio. However, despite the presence of conservative motives indicative of TcDH, the putative TcDH of the halophilic SOB have a low overall amino acid similarity to the Thioalkalivibrio enzyme, and also the surrounding genes in the TcDH locus were different. In particular, an alternative copper transport system Cus is present instead of Cop and a putative zero-valent sulfur acceptor protein gene appears just before TcDH. Moreover, in contrast to the thiocyanate-oxidizing Thioalkalivibrio species, both genomes of the halophilic SOB contained a gene encoding the enzyme cyanate hydratase. The sulfur-oxidizing pathway in the genome of Thiohalobacter includes a Fcc type of sulfide dehydrogenase, a rDsr complex/AprAB/Sat for oxidation of zero-valent sulfur to sulfate, and an incomplete Sox pathway, lacking SoxCD. The sulfur oxidation pathway reconstructed from the genome of Guyparkeria sp. SCN-R1 was more similar to that of members of the Thiomicrospira-Hydrogenovibrio group, including a Fcc type of sulfide dehydrogenase and a complete Sox complex. One of the outstanding properties of Thiohalobacter is the presence of a Na+-dependent ATP synthase, which is rarely found in aerobic Prokaryotes.Overall, the results showed that, despite an obvious difference in the general sulfur-oxidation pathways, halophilic and haloalkaliphilic SOB belonging to different genera within the Gammaproteobacteria developed a similar unique thiocyanate-degrading mechanism based on the direct oxidative attack on the sulfane atom of thiocyanate.

Biosynthesis and biodegradation of microorganisms critically underpin the development of biotechnology, new drugs and therapies, and environmental remediation. However, most uncultured microbial species along with their metabolic capacities in extreme environments, remain obscured. Here we unravel the metabolic potential of microbial dark matters (MDMs) in four deep-inland hypersaline lakes in Xinjiang, China. Utilizing metagenomic binning, we uncovered a rich diversity of 3030 metagenome-assembled genomes (MAGs) across 82 phyla, revealing a substantial portion, 2363 MAGs, as previously unclassified at the genus level. These unknown MAGs displayed unique distribution patterns across different lakes, indicating a strong correlation with varied physicochemical conditions. Our analysis revealed an extensive array of 9635 biosynthesis gene clusters (BGCs), with a remarkable 9403 being novel, suggesting untapped biotechnological potential. Notably, some MAGs from potentially new phyla exhibited a high density of these BGCs. Beyond biosynthesis, our study also identified novel biodegradation pathways, including dehalogenation, anaerobic ammonium oxidation (Anammox), and degradation of polycyclic aromatic hydrocarbons (PAHs) and plastics, in previously unknown microbial clades. These findings significantly enrich our understanding of biosynthesis and biodegradation processes and open new avenues for biotechnological innovation, emphasizing the untapped potential of microbial diversity in hypersaline environments., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2023 The Authors.)

The genomes of Thiohalobacter thiocyanaticus and Guyparkeria (formerly known as Halothiobacillus) sp. SCN-R1, two gammaproteobacterial halophilic sulfur-oxidizing bacteria (SOB) capable of thiocyanate oxidation via the "cyanate pathway", have been analyzed with a particular focus on their thiocyanate-oxidizing potential and sulfur oxidation pathways. Both genomes encode homologs of the enzyme thiocyanate dehydrogenase (TcDH) that oxidizes thiocyanate via the "cyanate pathway" in members of the haloalkaliphilic SOB of the genus Thioalkalivibrio. However, despite the presence of conservative motives indicative of TcDH, the putative TcDH of the halophilic SOB have a low overall amino acid similarity to the Thioalkalivibrio enzyme, and also the surrounding genes in the TcDH locus were different. In particular, an alternative copper transport system Cus is present instead of Cop and a putative zero-valent sulfur acceptor protein gene appears just before TcDH. Moreover, in contrast to the thiocyanate-oxidizing Thioalkalivibrio species, both genomes of the halophilic SOB contained a gene encoding the enzyme cyanate hydratase. The sulfur-oxidizing pathway in the genome of Thiohalobacter includes a Fcc type of sulfide dehydrogenase, a rDsr complex/AprAB/Sat for oxidation of zero-valent sulfur to sulfate, and an incomplete Sox pathway, lacking SoxCD. The sulfur oxidation pathway reconstructed from the genome of Guyparkeria sp. SCN-R1 was more similar to that of members of the Thiomicrospira-Hydrogenovibrio group, including a Fcc type of sulfide dehydrogenase and a complete Sox complex. One of the outstanding properties of Thiohalobacter is the presence of a Na+-dependent ATP synthase, which is rarely found in aerobic Prokaryotes.Overall, the results showed that, despite an obvious difference in the general sulfur-oxidation pathways, halophilic and haloalkaliphilic SOB belonging to different genera within the Gammaproteobacteria developed a similar unique thiocyanate-degrading mechanism based on the direct oxidative attack on the sulfane atom of thiocyanate. [ABSTRACT FROM AUTHOR]

The distribution and population dynamics of Ostracoda and their response to environmental factors have been analyzed in Crimean hypersaline lakes based on data from a long-term monitoring study (2005–2016). Only one representative of this class, Eucypris mareotica (Fischer, 1855), occurs in these lakes. The species was recorded in the Crimean lakes at a maximum salinity of 300 g/L. The frequency of occurrence of this species correlated negatively with salinity. This species reached high abundances in plankton (650 000 ind./m3), benthos (565 000 ind./m2), and floating mats of filamentous green algae Cladophora spp. (9 900 000 ind./kg of wet weight of the mat). Ostracods were shown to reduce the concentration of calcium and magnesium in the water as a result of using these elements for the construction of their shells. The possibility of using the shells of ostracods for paleoclimatic and palaeolimnological reconstructions was discussed. [ABSTRACT FROM AUTHOR]

Two strains of neutrophilic haloaloarchaea were selectively enriched from hypersaline lakes in southwestern Siberia using β-1,3-glucans as a substrate. The strains were nearly identical in their phenotypes and according to phylogenomic analysis, and represent a distant novel species group in the genus Halapricum of the family Haloarculaceae. The main phenotypic property of the novel isolates is the ability to hydrolyze and grow with the polysaccharides curdlan and pachyman. Such potential has, to date, not been seen in any other haloarchaea in pure cultures. The strains are obligately aerobic saccharolytics. Apart from the insoluble β-1,3-glucans, they utilized soluble α-glucans (starch, pullulan and glycogen) and a limited number of sugars. The major ether-bound polar phospholipids include PGP-Me and PG. The glyco- and sulfolipids were absent. The major respiratory menaquinone is MK-8:8. On the basis of their unique physiological properties and the results of phylogenomic analysis, the isolates are suggested to be classified into a novel species Halapricum hydrolyticum sp. nov. (type strain HArc-curdl5-1T = DSM 114193T = UQM 41587T). [ABSTRACT FROM AUTHOR]

Halophilic and halotolerant microorganisms represent promising sources of salt-tolerant enzymes that could be used in various biotechnological processes where high salt concentrations would otherwise inhibit enzymatic transformations. Considering the current need for more efficient biocatalysts, the present study aimed to explore the microbial diversity of five under- or uninvestigated salty lakes in Romania for novel sources of hydrolytic enzymes. Bacteria, archaea and fungi were obtained by culture-based approaches and screened for the production of six hydrolases (protease, lipase, amylase, cellulase, xylanase and pectinase) using agar plate-based assays. Moreover, the phylogeny of bacterial and archaeal isolates was studied through molecular methods. From a total of 244 microbial isolates, 182 (74.6%) were represented by bacteria, 22 (9%) by archaea, and 40 (16.4%) by fungi. While most bacteria synthesized protease and lipase, the most frequent hydrolase produced by fungi was pectinase. The archaeal isolates had limited hydrolytic activity, being able to produce only amylase and cellulase. Among the taxonomically identified isolates, the best hydrolytic activities were observed in halotolerant bacteria belonging to the genus Bacillus and in extremely halophilic archaea of the genera Haloterrigena and Halostagnicola. Therefore, the present study highlights that the investigated lakes harbor various promising species of microorganisms able to produce industrially valuable enzymes.

Chloroform (CF) is an environmental contaminant that can be naturally formed in various environments ranging from forest soils to salt lakes. Here we investigated CF removal potential in sediments obtained from hypersaline lakes in Western Australia. Reductive dechlorination of CF to dichloromethane (DCM) was observed in enrichment cultures derived from sediments of Lake Strawbridge, which has been reported as a natural source of CF. No CF removal was observed in abiotic control cultures without artificial electron donors, indicating biotic CF dechlorination in the enrichment cultures. Increasing vitamin B12 concentration from 0.04 to 4 µM in enrichment cultures enhanced CF removal and reduced DCM formation. In cultures amended with 4 µM vitamin B12 and 13C labelled CF, formation of 13CO2 was detected. Known organohalide-respiring bacteria and reductive dehalogenase genes were neither detected using quantitative PCR nor metagenomic analysis of the enrichment cultures. Rather, members of the order Clostridiales, known to co-metabolically transform CF to DCM and CO2, were detected. Accordingly, metagenome-assembled genomes of Clostridiales encoded enzymatic repertoires for the Wood-Ljungdahl pathway and cobalamin biosynthesis, which are known to be involved in fortuitous and nonspecific CF transformation. This study indicates that hypersaline lake microbiomes may act as a filter to reduce CF emission to the atmosphere.

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. [ABSTRACT FROM AUTHOR]

Lakes from semiarid areas are generally temporary and saline, depending on the precipitation cycles. The negative effect of salinity on zooplankton richness when a lake dries up is well known, but much less is known about the outcome when a lake reduces its salinity because of rainfall events. Parque Luro Reserve is located in Argentina’s semiarid area, and it has a hypersaline shallow lake with extreme variations of depth and salinity. The objective of this research was to analyze the changes in zooplankton diversity when the lake’s salinity decreased. We also analyzed the hatching conditions of Artemia persimilis Piccinelli and Prosdocimi, 1968 and the grazing effect of this species on the algal community. We incubated lake sediments in microcosms with lake water for 45 days at salinities between 25 and 300 g L −1 . The only species that hatched at salinities less than or equal to 100 g L −1 was A. persimilis . Hatching at higher salt concentrations, as observed in the field, would only occur if occasional rainfall produced a vertical stratification of salinity. The density and biomass of Artemia (dominated by post-naupliar stages) peaked at 50 g L −1 . At salinities less than or equal to 100 g L −1 , phytoplankton was not abundant, while periphyton was very abundant. The inverse relationship between A. persimilis and phytoplankton biomasses allowed us to corroborate a strong grazing effect of Artemia . The absence of other zooplankton species could be due to egg bank deterioration caused by the persistence of long-term hypersaline conditions. If other species appeared, they would by necessity have come from external sources. [ABSTRACT FROM AUTHOR]

Surface waters from hypersaline lakes of Cojocna Balneary Resort, Transylvania, Romania have been investigated in raw form, using Raman spectroscopy techniques. These lakes are usually exposed to high touristic influx mainly in summer months, due to their balneotherapeutic benefits. Therefore, chemical composition of waters and its variability is of high interest. Here we present spectroscopic characteristics of the lakes, obtained by Raman scattering techniques, probing several water samples collected in two consecutive years. Among the two lakes, Torok Lake showed 1.449 times higher sulfate concentration than the Great Lake in 2016 and 0.737 in 2017 respectively, according to the calculated ratio of the Raman band of sulfate at 979 cm-1 relative to water band. Chemical changes associated with the presence of different plankton species and their density fluctuations were reflected in changes in resonance Raman scattering signal of carotenoids during Artemia salina crustaceans blooming population in August, compared to July, in both years. Interestingly, the bloom appeared alternatively in two consecutive years and it is apparently correlated to lower sulfate level, as revealed by spectral data only. Raman data indicated the dynamic cycles in chemical composition of salt lakes. Such changes are certainly suitable for constant monitoring purpose of the balneotherapeutic salt water bodies via Raman spectroscopy. Both FT-Raman and dispersive Raman are suitable for this purpose. Fast analysis, without additional separation steps and chemicals consumption may provide information on the sulfate level and carotenoids. The results could be attractive for monitoring studies, or informative, for touristic purpose or aquaria hobby cultivars. [ABSTRACT FROM AUTHOR]

[Display omitted] • A simulation method which takes into account energy, mass and salt balances was designed to simulate the future fate of the Dead Sea. • Model results were verified against ∼ 100 years of lake level data. • An analytic novel diagnostic method was developed in this investigation to verify the simulation results. • A steep decline was observed in the first 100–200 years of simulation and then level decline becomes gradually asymptotic. • The lake will reach a quasi-steady state condition after several hundred years. An energy balance model run on a monthly time step for 800 years was developed to predict the future level, areal extent and temperature of the Dead Sea under different scenarios of freshwater input and atmospheric boundary conditions. The model integrates energy, water and salt balances. The bathymetry of the Dead Sea was derived from high-resolution digital elevation data. Model results were verified against measured lake level for the period 1928 through 2022. Predicted levels are very close to observed values as demonstrated by three statistical measures. The monthly temperatures of the mixed layer as predicted by the model were also commensurate with observational results and satellite derived data. Future simulation predictions were verified against a novel diagnostic analytic method developed in this investigation. The newly developed method has the potential to approximate the equilibrium activity and temperature of hypersaline lakes under specified freshwater inflow and atmospheric forcings. Results show that the future level, areal extent and temperature of the Dead Sea will be contingent on freshwater inflow and the prevailing atmospheric forcings. Projections indicate that the Dead Sea will end up as a dwarfed hypersaline hot lake. The time span needed for the Dead Sea to reach a quasi-steady state equilibrium is several hundred years. Simulations results presented in this investigation are expected to be approximate given the complexity of the system, the long integration time involved, and uncertainties brought about by climate vagaries and model parameterizations. [ABSTRACT FROM AUTHOR]

Nitrogen inputs to Great Salt Lake (GSL), located in the western USA, were quantified relative to the resident nitrogen mass in order to better determine numeric nutrient criteria that may be considered at some point in the future. Total dissolved nitrogen inputs from four surface-water sources entering GSL were modeled during the 5-year study period (2010-2014) and ranged from 1.90 × 10 to 5.56 × 10 kg/year. The railroad causeway breach was a significant conduit for the export of dissolved nitrogen from Gilbert to Gunnison Bay, and in 2011 and 2012, net losses of total nitrogen mass from Gilbert Bay via the Causeway breach were 9.59 × 10 and 1.51 × 10 kg. Atmospheric deposition (wet + dry) was a significant source of nitrogen to Gilbert Bay, exceeding the dissolved nitrogen load contributed via the Farmington Bay causeway surface-water input by >100,000 kg during 2 years of the study. Closure of two railroad causeway culverts in 2012 and 2013 likely initiated a decreasing trend in the volume of the higher density Deep Brine Layer and associated declines in total dissolved nitrogen mass contained in this layer. The large dissolved nitrogen pool in Gilbert Bay relative to the amount of nitrogen contributed by surface-water inflow sources is consistent with the terminal nature of GSL and the predominance of internal nutrient cycling. The opening of the new railroad causeway breach in 2016 will likely facilitate more efficient bidirectional flow between Gilbert and Gunnison Bays, resulting in potentially substantial changes in nutrient pools within GSL. [ABSTRACT FROM AUTHOR]