Inland Salt Lakes Research Articles

Genetic structure of ten Artemia populations from China: cumulative effects of ancient geological events, climatic changes, and human activities

This study investigated the population genetics and distribution patterns of Artemia populations from ten inland salt lakes in China. A total of 1,274,698 Artemia single nucleotide polymorphisms (SNPs) were identified. The results showed that these populations could be geographically and genetically divided into four distinct groups, and that the Tibetan populations were further divided into two subpopulations with a trend of decreasing genetic diversity from west to east. The Tibetan population had the highest genetic diversity, whereas the Shanxi population had the lowest. There was moderate genetic differentiation between the Tibetan populations and greater genetic differentiation between the Xinjiang and Shanxi populations. IBD (isolation by distance) suggested that geographical isolation contributes to genetic differentiation. In addition, there was some degree of gene flow among the ten populations, with A. sinica showing unidirectional gene flow in all populations in the eastern Nagri region. Species distribution modeling showed that mean annual temperature, temperature seasonality, and annual precipitation were the main environmental factors affecting the distribution of Artemia populations and suitable habitats for Tibetan populations will be further reduced in the future. It is necessary to strengthen the protection of germplasm resources and formulate scientific protocols for the sustainable development and utilization of Artemia resources.

Geoecological evolution of New Zealand’s only inland salt lake

ABSTRACT The Sutton Salt Lake is a rare occurrence of an inland evaporative saline lake on a small landmass with a temperate maritime climate. The lake lies on a bed of impermeable loess silt in a 2 ha depression between tor ridges of Otago Schist in inland east Otago. A rim of salt-tolerant plants (halophytes) occurs around parts of the lake margin. The vegetated lake margin has encroached laterally on to the lake bed by 5–30 m over the past 50 years. Salinity in the lake is dominated by Na and Cl (molar ratio ∼1) that has been concentrated by annual cycles of evaporation and replenishment by rain with marine aerosols. Drying lake margin sediments lose NaCl via rain-driven recycling back into the lake, with the formation of a salt crust that contains Ca, Mg and Na carbonate minerals, gypsum, and remnant halite. The lake and lake sediment chemistry are affected by carbonate dissolution and deposition, and more than 10-fold Ca–Mg carbonate supersaturation in lake waters contributes to elevated water pH (8.9–9.3). Geoecological evolution of the lake margin involves the encroachment of exotic weeds behind active halophytic habitats as dilute surface water lowers salinity.

Exploitation of inland salt lake water by dilution and nutrient enrichment to cultivate Vischeria sp. WL1 (Eustigmatophyceae) for biomass and oil production

Salt lakes are significant components of global inland waters. Salt lake (SL) water can provide precious mineral resource for microbial growth. The prospect of utilizing diluted SL water for cultivation of a terrestrial oil-producing microalga Vischeria sp. WL1 was evaluated under laboratory conditions. Based on the detected mineral element composition, the water from Gouchi Salt Lake was diluted 2, 4, 6 and 8 folds and used with supplementation of additional nitrogen, phosphorus and iron (SL+ water). It was found that 4 folds diluted SL+ water was most favorable for biomass and oil production. When cultivated in this condition, Vischeria sp. WL1 gained a biomass yield of 0.82 g L−1 and an oil yield of 0.56 g L−1 after 24 days of cultivation, which is comparable to the optimum productivity we previously established. In addition, total monounsaturated fatty acid contents (64.4∼68.1 %) of the oils resulted from cultures in diluted SL+waters were higher than that in the control (55.5 %). It was also noteworthy that in all these cultures the oil contents (652.0∼681.0 mg g−1) accounted for the most of the biomass, which are far more than the protein and starch contents. This study demonstrates the feasibility of using SL water as a cost-effective mineral resource to cultivate microalgae for biomass and oil production.

A novel remote sensing index for brine shrimp (Artemia) slick detection in salt lakes

Artemia (brine shrimp) are a widely distributed zooplankton in inland salt lakes and artificial ponds throughout the tropical, subtropical, and temperate zones. Notably, they are of great importance to fishery production and salt lake ecosystem health. Recently, Artemia resources have been threatened by habitat deterioration and overfishing, which mandate adequate monitoring; however, advanced methods for detecting Artemia from remote sensing images have rarely been discussed. Accordingly, this study explored the possibility of detecting the adult Artemia (Artemia) slicks using multispectral optical sensors by analyzing their unique aggregation patterns and consistent optical properties. After measuring Artemia spectra in the field, reflectance troughs were observed at ∼431 nm and ∼ 560 nm, which were deemed likely related to the absorption of β-carotene and heme, respectively, resulting in their reddish color. These characteristics could also be used to differentiate Artemia from other confounding features, including clean water and chlorophyll-a (Chl-a)- or suspended particulate matter (SPM)- dominated water. Based on these spectral signatures, a brine shrimp index (BSI) was developed using the difference between the reflectance at NIR band and a linear baseline between green and SWIR1 bands of Landsat-8 Operational Land Imager (OLI) imagery. Further, a BSI-based Artemia slick pixel extraction method was proposed. Using observation geometry information in conjunction with the BSI value of entire lakes, the BSI thresholds for the Artemia-containing pixels were automatically determined, and > 80% overall accuracy was achieved. The index performance was affected by the presence of residual cloud shadows, high water turbidity, and mixed pixels with low Artemia density. Moreover, BSI values were found to be relatively insensitive to atmospheric signals. It was shown here that the BSI detection limit was >0.53% Artemia subpixel coverage under clean water conditions; whereas a higher coverage was required to separate Artemia from Chl-a- or SPM- dominated water. The mean absolute percentage difference of BSI values calculated from Rayleigh-corrected and top-of-atmosphere (TOA) reflectance was <4% compared with surface reflectance derived BSI, and the relative difference in coverage area was < ±10%. Lastly, time series analyses of Lake Aibi in northwest China and the Great Salt Lake in North America revealed that the annual areal coverage estimation of Artemia slicks based on BSI was a positive indicator of Artemia harvesting, which can facilitate the Artemia resource management.

Plastic Debris in Nests of Two Water Bird Species Breeding on Inland Saline Lakes in a Mediterranean Biosphere Reserve.

Despite more studies being carried out to know the impacts associated with plastic debris and much effort being spent on marine ecosystems, the impacts of plastics on terrestrial and freshwater species remain largely unknown. Here, we explored the presence of anthropogenic materials in nests of two wader species, the gull-billed tern (Gelochelidon nilotica) and the black-winged stilt (Himantopus himantopus), breeding on the inland salt lakes in the "La Mancha Húmeda" Biosphere Reserve, Central Spain. We revealed the presence of anthropogenic debris, mainly macroplastics (&gt;5 mm), in 2.4% and 12.5% of the sampled nests of the gull-billed tern and the black-winged stilt, respectively. The fragments found in nests ranged from 8 mm to 257 mm for the gull-billed tern and from 7 mm to 19 mm for the black-winged stilt. This debris showed no clear pattern of color or size and probably originated both in the agricultural activities in the surroundings and domestic refuse. Although we did not detect any pernicious impacts on adults or chicks (e.g., entangled, injured, or dead individuals), the presence of plastics and other human waste directly placed in nests located in a protected area should warn us about the ubiquity of these pollutants, and the endocrine and immunological effects, among others, that may reduce the recruitment of new animals to the population should be assessed.

Halobaculum rubrum sp. nov., an extremely halophilic archaeon isolated from a salt lake.

A halophilic archaeal strain, designated C46T, was isolated from an inland salt lake in Qinghai Province, PR China. Results of phylogenetic analysis based on 16S rRNA gene sequences indicated that strain C46T belongs to the genus Halobaculum, and the closest phylogenetic relative is Halobaculum gomorrense DSM 9297T with 97.7 % similarity. Despite this, strain C46T was more related to Halobaculum saliterrae WSA2T than other members of the genus Halobaculum based on genome comparison and analysis, and the average nucleotide identity, in silico DNA-DNA hybridization, amino acid identity and percentage of conserved protein values between the two strains were 89.1, 53.3, 89.2 and 75.6 %, respectively, which are lower than the cutoff values proposed for species delimitation. The physiological, biochemical, genetic and genomic characteristics of strain C46T were different from those of its closest phylogenetic neighbours, which indicated that this strain represents a novel species of the genus Halobaculum, for which the name Halobaculum rubrum sp. nov. is proposed. The type strain is C46T (=CGMCC 1.13737T=JCM 32959T).

Phytogeography, ecology and conservation of the genus Limonium (Plumbaginaceae) in Turkey and a taxonomic revision

This article examines the distribution, ecology, and threat categories of the genus Limonium, (Plumbaginaceae) in Turkey. The specimens of Limonium used in this study were either collected during the field excursions carried out in the country over the last 10 years or otherwise stored at various herbaria. Most of the species are locally distributed endemics confined to saline habitats either on the coastal ecosystems of the Mediterranean region or inland salt lakes. They are threatened by excessive grazing, habitat alterations and global warming. A concise taxonomic revision of Limonium in Turkey, covering 27 taxa (25 species and two varieties), is also presented including keys to the species and varieties. So far, three new endemic taxa, Limonium davisii, sp. nov., Limonium lilacinum var. laxiflorum, var. nov., and Limonium globuliferum var. subglobosum, var. nov., are described for the first time. The center of Limonium diversity, according to our survey, lies in the Mediterranean Irano-Turanian region, where 14 endemic taxa (seven of them known from one locality), seven non-endemic rare taxa and six widely distributed taxa are found. We propose that threat categories for the taxa at global level be as follows: seven Critically Endangered (CR), three Endangered (EN), four Vulnerable (VU) and 13 Least Concerned. The threatened species are mainly confined to salty habitats on the coast of Mediterranean or the inland salt lakes.

Natronorubrum halophilum sp. nov. isolated from two inland salt lakes.

Two halophilic archaeal strains, SHR37T and NEN6, were isolated from salt lakes located in the Tibet and Xinjiang regions of China. The two strains were found to form a single cluster (99.9% and 99.3% similarity, respectively) separating them from the six current members of Natronorubrum (94.7-96.9% and 86.1-90.8% similarity, respectively) on the basis of the 16S rRNA and rpoB' gene sequence similarities and phylogenetic analysis. Diverse phenotypic characteristics differentiate strains SHR37T and NEN6 from current Natronorubrum members. Their polar lipids are C20C20 and C20C25glycerol diether derivatives of PG, PGP-Me, and a major gycolipid chromatographically identical to disulfated mannosyl glucosyl diether (S2-DGD). Four minor unidentified gycolipids are also present. The OrthoANI and in silico DDH values of the two strains were 97.3% and 76.1%, respectively, which were much higher than the threshold values proposed as a species boundary (ANI 95-96% and in silico DDH 70%), which revealed that the two strains represent one species; the two values (ANI 79.0-81.9% and in silico DDH 23.5-25.7%) of the strains examined in this study and the current members of Natronorubrum are much lower than the recommended threshold values, suggesting that strains SHR37T and NEN6 represent a genomically different species of Natronorubrum. These results showed that strains SHR37T (= CGMCC 1.15233T = JCM 30845T) and NEN6 (= CGMCC 1.17161) represent a novel species of Natronorubrum, for which the name Natronorubrum halophilum sp. nov. is proposed.

A Review on the Status of Sambhar Wetland Bird Tragedy

Sambhar Lake is India’s largest inland salt lake. It is a shallow Ramsar wetland Subject to seasonal fluctuations. The site is important for a variety of wintering water birds, including large numbers of flamingos. Human activities consist of salt production and livestock grazing. It is also an Important Bird Area (IBA) due to migratory avifaunal population, especially flamingo and waterfowl. Presence of salt-tolerant algae makes the lake one of the most important wintering areas for flamingos. The specialized algae and bacteria growing in the lake provide striking water colors and support the lake ecology that, in turn, sustains the migrating waterfowl. Current conservational threats owing to the drastic reduction in water spread and anthropogenic pressures were major concerns till Oct.2019. The death of thousands of birds was detected on 11th November 2019 which belonged to 25 different species. Majority of were migratory birds and a few local species The main cause identified was avian botulism. The paper reviews the cause and efforts taken to revive it as a safe wetland.

Review on integrated production of the brine shrimp Artemia in solar salt ponds

AbstractThe brine shrimp Artemia is a highly required, convenient and cost‐effective live food used in fish and shellfish larviculture. Its cysts, originating from a limited number of inland salt lakes, are traded worldwide. Over the past decades, Artemia pond production in solar saltworks, integrated with salt production, has emerged as an alternative to cope with possible cyst shortages and high prices on the international market and as a tool to fulfill local cyst and Artemia biomass demands associated with local and regional aquaculture developments. This article reviews the principles of Artemia pond production and how it is practiced in terms of general management. It also describes the distinctive features that have evolved in various countries, due to geographical, environmental and socio‐economic characteristics and the local aquaculture context. It highlights the lessons that may be learnt from previous successes and failures for new areas where the technique may be introduced. The principles of Artemia pond production are also discussed in the light of global and local Artemia biodiversity, as its protection is key to support the sustainability of the aquaculture industry. This review pioneers in bringing this information, much of which was restricted to grey literature until now, under the attention of the international scientific audience. Future research and development should focus on continued proper management to secure cyst production and to maximize cyst quantities. Moreover, using the information provided by the Artemia genome will allow as well to strive for improved cyst quality, by producing strains with specific market characteristics.

Spatial distribution and genesis of salt on the saline playa at Qehan Lake, Inner Mongolia, China

Inland salt lakes and saline wetlands are intricate systems in which moisture and salinity are continuously changing and especially sensitive to climate change and human pressure. Remote sensing helps to monitor the dynamic changes in the moisture and salinity of salt lakes and saline wetlands. Based on the Landsat 8 satellite data, this paper developed a multivariable linear regression model (MLRM) to predict the spatial distribution of salt on the saline playa at the Qehan Lake in Inner Mongolia, China. The developed MLRM used the remote sensing spectral indices and the Tasseled Cap Transformation wetness band (TCTW) as a variable. By using the TCTW and the surface temperature inversion data, the response of salt to surface moisture and temperature in the dry lake bed was explored. The results showed: The MLRM with brightness index (BI) and the TCTW as the auxiliary variables has the nice applicability (Radj2 = 0.598, RMSE = 1.640). The MLRM established using the vegetation index NDVI may be more applicable to environments where vegetation and salts were doped-together. Salt distribution in the Qehan Lake may be controlled by flat lake bed and miniature piedmonts. There was a significant correlation between measured soil electrical conductivity (EC) and TCTW, but no correlation with surface temperature. The influence of surface temperature on salt may be biased towards the time scale.

NaCl-saturated brines are thermodynamically moderate, rather than extreme, microbial habitats.

NaCl-saturated brines such as saltern crystalliser ponds, inland salt lakes, deep-sea brines and liquids-of-deliquescence on halite are commonly regarded as a paradigm for the limit of life on Earth. There are, however, other habitats that are thermodynamically more extreme. Typically, NaCl-saturated environments contain all domains of life and perform complete biogeochemical cycling. Despite their reduced water activity, ∼0.755 at 5 M NaCl, some halophiles belonging to the Archaea and Bacteria exhibit optimum growth/metabolism in these brines. Furthermore, the recognised water-activity limit for microbial function, ∼0.585 for some strains of fungi, lies far below 0.755. Other biophysical constraints on the microbial biosphere (temperatures of >121°C; pH > 12; and high chaotropicity; e.g. ethanol at >18.9% w/v (24% v/v) and MgCl2 at >3.03 M) can prevent any cellular metabolism or ecosystem function. By contrast, NaCl-saturated environments contain biomass-dense, metabolically diverse, highly active and complex microbial ecosystems; and this underscores their moderate character. Here, we survey the evidence that NaCl-saturated brines are biologically permissive, fertile habitats that are thermodynamically mid-range rather than extreme. Indeed, were NaCl sufficiently soluble, some halophiles might grow at concentrations of up to 8M. It may be that the finite solubility of NaCl has stabilised the genetic composition of halophile populations and limited the action of natural selection in driving halophile evolution towards greater xerophilicity. Further implications are considered for the origin(s) of life and other aspects of astrobiology.

Palaeoenvironmental significance of charophyte gyrogonites from Laguna de Gallocanta (Aragón, Spain)

At a distance of about 170 km from the Mediterranean, the inland salt lake Laguna de Gallocanta (995 m a.s.l.) is an important stop-over for thousands of migratory water birds and represents an athallasic occurrence of Lamprothamnium papulosum (Wallr.) J. Groves and Chara galioides DC., which were recorded growing in the lake until 1990. These two charophyte species are typically also known from Mediterranean coastal brackish water sites. The material studied here consists of (i) gyrogonites collected from surface sediments in Laguna de Gallocanta and (ii) fossil gyrogonites recovered from the upper 35 cm of a 75 cm core obtained from the lake. Detailed morphological and biometrical analysis of L. papulosum is provided and compared with previous data from South France. The size and shape of the gyrogonites from Laguna de Gallocanta differ greatly from populations growing in coastal sites. These differences are considered to be an adaptive morphological response to the particular hydro-chemical conditions prevailing in Laguna de Gallocanta whose salinity is due to the outwash of sulphate-rich waters from the underground. The distribution and frequency changes of the charophyte species along the core profile allow inferring palaeoecological changes marked by lake-level lowering and increasing salinity.

Chemical assessment of Sambhar Soda Lake, a Ramsar site in India

The Sambhar Soda Lake situated in Rajasthan, is the largest inland salt lake. The chemical assessment of this lake water is studied with respect to its abiotic characters. Monsoon and winter water sample analyses revealed that the lake water is hypersaline and highly alkaline in nature. The average maximum pH is 9.5 and salinity 30%, which is one of the unique features of this lake. As compared to monsoon water sample the winter sample contains remarkable concentration of various ions like sodium (9930 mg/L), chloride (7356 mg/L), bicarbonates (6080 mg/L), sulfate (9152 mg/L). Various metals were recorded from this sample analysis. The considerable amount of lead (1359 μg/L), cadmium (1416 μg/L), copper (2099 μg/L), and cobalt (2453 μg/L) metals were found from winter 2010 sample. As compare of to other saline lake and sea water the Sambhar Lake water chemistry is different, and require continuous monitoring.

Groundwater salinization in shallow aquifers adjacent to a low-altitude inland salt lake: a case study at Yuncheng Basin, northern China

Measurements of chemical composition and environmental isotopes were conducted to investigate the main geochemical processes controlling the salinization of shallow groundwater adjacent to an inland salt lake in the Yuncheng Basin. Hydrogeochemical and isotopic studies were carried out by collecting thirty shallow groundwater, two rainfalls, and one salt lake water samples from the study area. About 80 % of the shallow groundwater samples had total dissolved solids more than 500 mg/L, implying significant water-quality deterioration in the study area. Shallow groundwater showed a clear increased salinity along regional flow paths toward the center of the basin where a salt lake is located. Results of environmental isotopes, ionic ratio, and saturation indices’ calculation indicated that the major geochemical processes responsible for groundwater salinization included dissolution of evaporites (halite, gypsum, and mirabilite), cation exchange, and evapotranspiration. Groundwater salinization as a result of salt lake intrusion from the salt lake was limited to the northern shore of the lake.

Identifying the origin and geochemical evolution of groundwater using hydrochemistry and stable isotopes in the Subei Lake basin, Ordos energy base, Northwestern China

Abstract. A series of changes in groundwater systems caused by groundwater exploitation in energy base have been of great concern to hydrogeologists. The research aims to identify the origin and geochemical evolution of groundwater in the Subei Lake basin under the influence of human activities. Water samples were collected, and major ions and stable isotopes (δ18O, δD) were analyzed. In terms of hydrogeological conditions and the analytical results of hydrochemical data, groundwater can be classified into three types: the Quaternary groundwater, the shallow Cretaceous groundwater and the deep Cretaceous groundwater. Piper diagram and correlation analysis were used to reveal the hydrochemical characteristics of water resources. The dominant water type of the lake water was Cl-Na type, which was in accordance with hydrochemical characteristics of inland salt lakes; the predominant hydrochemical types for groundwater were HCO3–Ca, HCO3–Na and mixed HCO3–Ca–Na–Mg types. The groundwater chemistry is mainly controlled by dissolution/precipitation of anhydrite, gypsum, halite and calcite. The dedolomitization and cation exchange are also important factors. Rock weathering is confirmed to play a leading role in the mechanisms responsible for the chemical composition of groundwater. The stable isotopic values of oxygen and hydrogen in groundwater are close to the local meteoric water line, indicating that groundwater is of modern local meteoric origin. Unlike significant differences in isotopic values between shallow groundwater and deep groundwater in the Habor Lake basin, shallow Cretaceous groundwater and deep Cretaceous groundwater have similar isotopic characteristics in the Subei Lake basin. Due to the evaporation effect and dry climatic conditions, heavy isotopes are more enriched in lake water than in groundwater. The low slope of the regression line of δ18O and δD in lake water could be ascribed to a combination of mixing and evaporation under conditions of low humidity. Comparison of the regression line for δ18O and δD showed that lake water in the Subei Lake basin contains more heavily isotopic composition than that in the Habor Lake basin, indicating that lake water in the discharge area has undergone stronger evaporation than lake water in the recharge area. Hydrochemical and isotopic information of utmost importance has been provided to decision makers by the present study so that a sustainable groundwater management strategy can be designed for the Ordos energy base.

Halorussus ruber sp. nov., isolated from an inland salt lake of China.

Halophilic archaeal strain YC25(T) was isolated from Yuncheng salt lake in Shanxi, China. Cells of strain YC25(T) were observed to be pleomorphic rods, stained Gram-negative, and formed red-pigmented colonies on solid media. Strain YC25(T) was found to be able to grow at 25-50°C (optimum 37°C), at 1.4-4.8M NaCl (optimum 1.7M), at 0-1.0M MgCl2 (optimum 0.01M), and at pH 5.5-9.0 (optimum pH 6.5). The cells lysed in distilled water, and the minimal NaCl concentration to prevent cell lysis was found to be 8% (w/v). The major polar lipids of the strain were phosphatidylglycerol (PG), phosphatidylglycerol phosphate methyl ester (PGP-Me), phosphatidylglycerol sulfate (PGS), sulfated galactosyl mannosyl glucosyl diether (S-TGD-1), sulfated mannosyl glucosyl diether (S-DGD-1), galactosyl mannosyl glucosyl diether (TGD-1), mannosyl glucosyl diether (DGD-1), and an unknown diglycosyl diether (DGD-2) chromatographically identical to those of Halorussus rarus CGMCC 1.10122(T). The 16S rRNA gene and rpoB' gene of strain YC25(T) were phylogenetically related to the corresponding genes of Halorussus rarus CGMCC 1.10122(T) (94.3-95.4 and 91.5% nucleotide identity, respectively). The DNA G+C content of strain YC25(T) was determined to be 63.3mol%. The phenotypic, chemotaxonomic, and phylogenetic properties suggested that strain YC25(T) (=CGMCC 1.12122(T)=JCM 18363(T)) represents a new species of Halorussus, for which the name Halorussus ruber sp. nov. is proposed.

Extreme nomadism in desert waterbirds: flights of the banded stilt.

In contrast to well-studied Northern Hemisphere birds with spatially and temporally predictable seasonal migrations, waterbirds in desert biomes face major challenges in exploiting stochastic, rich, yet short-lived resource pulses in vast arid landscapes, leading to the evolution of nomadic behaviour. An extreme example is the banded stilt (Cladorhynchus leucocephalus), an opportunistic colonial breeder at remote inland salt lakes after infrequent rain events. Using satellite telemetry on 21 birds (tracked for a mean of 196.2 days), we reveal extensive, rapid and synchronized movement among individuals to and from salt lakes. Two birds left coastal refugia for the inland following rain, flying 1000-2000 km, while 12 others rapidly moved a mean of 684 km (range 357-1298 km) away from drying inland sites to the coast. Two individuals moved longitudinally across the continent, departing and arriving at the same points, yet travelling very different routes; one bird moving more than 2200 km in less than 2.5 days, the other more than 1500 km in 6 days. Our findings reveal movements nearly twice as long and rapid as recorded in other desert waterbirds. We reveal capability to rapidly detect and exploit ephemeral wetland resource pulses across the stochastic Australian desert.

Techniques of Preventing Subgrade from Salinization for Qarham to Golmud Expressway

Qarham to Golmud expressway is the first high-grade road in Qarham salt lake, which is regarded as the most enormous inland salt lake in China, moreover, it is the first expressway built on the inland salt lake in China. There is high and excessive saline soil distributed over this area whose thickness is no less than 20m, but the average subgrade height of the expressway is only 2m. A great many of measures are taken for the construction of the subgrade to prevent salt migrating from foundation to roadbed and pavement, which will cause disasters of secondary salinization in roadbed and pavement. By paving testing road at the site and detecting the efficiency of the measures in preventing salt, the paper put forward the technique of preventing subgrade from salinization for Qarham to Golmud expressway. The results of testing and detecting demonstrate that the height of salt migration is only 45cm in subgrade under the condition of brine supply, which is less than the height of subgrade. So it is efficient to keep the roadbed and pavement from the erosion of salt; The settlement of road surface was about 0~2mm among 3 months since the highways had been opened to traffic for two years, and uneven settlement and other diseases caused by the secondary salinization were not appeared, which showed that the measures of salinization prevention (salt resistance) were taken well to achieve the design purposes.

Culturable diversity of halophilic bacteria in foreshore soils.

Halophilic bacteria are commonly found in natural environments containing significant concentration of NaCl such as inland salt lakes and evaporated sea-shore pools, as well as environments such as curing brines, salted food products and saline soils. Dependence on salt is an important phenotypic characteristic of halophilic bacteria, which can be used in the polyphasic characterization of newly discovered microorganisms. In this study the diversity of halophilic bacteria in foreshore soils of Daecheon, Chungnam, and Saemangeum, Jeonbuk, was investigated. Two types of media, namely NA and R2A supplemented with 3%, 5%, 9%, 15%, 20% and 30% NaCl were used. More than 200 halophilic bacteria were isolated and BOX-PCR fingerprinting analysis was done for the typing of the isolates. The BLAST identification results showed that isolated strains were composed of 4 phyla, Firmicutes (60%), Proteobacteria (31%), Bacteriodetes (5%) and Actinobacteria (4%). Isolates were affiliated with 16 genera and 36 species. Bacillus was the dominant genus in the phylum Firmicutes, comprising 24% of the total isolates. Halomonas (12%) and Shewanella (12%) were also found as the main genera. These findings show that the foreshore soil of Daecheon Beach and Saemangeum Sea of Korea represents an untapped source of bacterial biodiversity.