Saline-alkaline Environment Research Articles

Long-term rice cultivation enhances root development and yields by improving the structural properties of soil aggregates in saline–alkaline environments

Rice cultivation has the ability to improve saline soils. However, the effects of long-term rice cultivation on saline soil chemistry, salt ions, root characteristics, and aggregate formation remain unclear. In this study, the impact of different planting durations (1, 3, 5, 8, and 10 years) on the spatial and temporal transport of soil salts, soil chemical properties, distribution and stability of aggregates, root characteristics, and yields, were assessed. Long-term rice cultivation reduced soil pH, exchangeable sodium percentage (ESP), and EC in the 0-60cm soil layer compared to 1Y (5.45%, 61.57%, and 81.87% reduction in topsoil (0-20cm) and 8.54%, 72.82%, and 71.94 in subsoil (20-60cm), respectively). However, the soil organic matter (OM), alkaline nitrogen (AN), phosphorus (AP), and potassium (AK) increased (217.09%, 90.18%, 89.23%, and 179.18% increase in topsoil and 223.72%, 81.24%, 174.28%, and 172.57% increase in subsoil, respectively). Additionally, the Cl-, K+, and Na+ in the soil gradually leached downward with the increase in the duration of rice cultivation (55.87%、36.08%、59.80%). Simultaneously, the increased duration markedly elevated the soil macroaggregate content (11.43%-20.04% by dry-sieving and 53.48%-288.09% by wet-sieving), clayey grain content (59.17%-198.33%), and soil aggregate stability, especially for 8Y and 10Y. The improved soil structure and root characteristic under long-term rice cultivation conditions increased the yield (28.89-54.81%). Partial least squares path model displayed that rice cultivation affected the aggregate stability, root characteristics, and rice yield via the corresponding chemical properties (pH, EC, and ESP), nutrient contents (AN, AP, AK, and SOM), and salt ion contents (Cl-, K+, and Na+). These findings are critical to understanding aggregate formation in saline soils.

Study on the physiological responses and tolerance mechanisms to subchronic carbonate alkalinity exposure in the gills of Paramisgurnus dabryanus

Given the reduction of freshwater resources, saline-alkaline aquaculture has emerged as an effective approach to expand the fishery's accessible space. High carbonate alkalinity (CA) is a major stressor for aquatic organisms in saline-alkaline environments. Paramisgurnus dabryanus is a potential species for culture in saline-alkaline water, making it an ideal model for investigating the physiological responses and tolerance mechanisms to CA exposure in freshwater fishes. In the current study, P. dabryanus were exposed to 15 and 30mmol/L NaHCO3, combining blood biochemical, gill histological, transcriptomic, and metabolomic methods for conjoint analysis of response mechanisms. After 28-d exposure, the gill ventilation frequency of P. dabryanus decreased significantly, gill lamellae twisted and atrophied, and gill filament epithelial cells proliferated, potentially limiting gas exchange, whereas the accessory air-breathing frequency increased significantly, possibly for greater oxygen uptake. Serum osmolality and blood pH remained relatively steady, while serum ammonia levels rose significantly. A total of 3718 differentially expressed genes (DEGs) and 205 differential metabolites (DMs) were identified between the control group and 30mmol/L NaHCO3 group, involved in ion transport (Na+/K+-ATPase, V-type ATPase, carbonic anhydrase, and ABC transporters), ammonia transport (Rh glycoproteins and Aquaporins), amino acid metabolism, carbohydrate metabolism, and fatty acid metabolism. Furthermore, DEGs were significantly associated with cell-cell/ extracellular matrix interaction and protein synthesis. An integrated multi-omics analysis revealed the activation of carbon metabolism and TCA cycle. These results indicate that in response to CA exposure, P. dabryanus may facilitate carrier-mediated ion and ammonia transport to maintain the internal osmotic equilibrium and lessen the deleterious effects of blocked ammonia excretion. Meanwhile, amino acid metabolism and protein synthesis are disturbed, P. dabryanus can modulate carbohydrate catabolism to maintain energy homeostasis. The above findings provide novel insights into saline-alkaline adaptation in freshwater fishes, paving the way for future research and development of saline-alkaline-tolerant Cobitidae strains.

Exploration of Synergistic Regulation Mechanisms of Cerebral Ganglion and Muscle in Eriocheir sinensis Activated in Response to Alkalinity Stress.

The cerebral ganglion and muscle are important regulatory tissues in Eriocheir sinensis. Therefore, it is of great significance to explore their synergistic roles in this organism's anti-stress response. In this study, proteomics, metabolomics, and combination analyses of the cerebral ganglion and muscle of E. sinensis under alkalinity stress were performed. The cerebral ganglion and muscle played a significant synergistic regulatory role in alkalinity adaptation. The key regulatory pathways involved were amino acid metabolism, energy metabolism, signal transduction, and the organismal system. They also played a modulatory role in the TCA cycle, nerve signal transduction, immune response, homeostasis maintenance, and ion channel function. In conclusion, the present study provides a theoretical reference for further research on the mechanisms regulating the growth and development of E. sinensis in saline-alkaline environments. In addition, it provides theoretical guidelines for promoting the vigorous development of the E. sinensis breeding industry in saline-alkaline environments in the future.

Differential Strategies of Two Arbuscular Mycorrhizal Fungi Varieties in the Protection of Lycium ruthenicum under Saline-Alkaline Stress.

To delve into the growth and physiological adaptations exhibited by the economically vital black wolfberry (Lycium ruthenicum) upon inoculation with arbuscular mycorrhizal fungi (AMF) under varying levels of saline-alkaline stress A series of pot experiments were conducted in a gradient saline-alkaline environment (0, 200, 400 mM NaCl: NaHCO3 = 1:1). One-year-old cuttings of black wolfberry, inoculated with two AMF species-Funneliformis mosseae (Fm) and Rhizophagus intraradices (Ri)-served as the experimental material, enabling a comprehensive analysis of seedling biomass, chlorophyll content, antioxidant enzyme activities, and other crucial physiological parameters. This study demonstrated that both Fm and Ri could form a symbiotic relationship with the root of Lycium ruthenicum. Notably, Fm inoculation significantly bolstered the growth of the underground parts, while exhibiting a remarkable capacity to scavenge reactive oxygen species (ROS), thereby effectively mitigating membrane oxidative damage induced by stress. Additionally, Fm promoted the accumulation of abscisic acid (ABA) in both leaves and roots, facilitating the exclusion of excess sodium ions from cells. Ri Inoculation primarily contributed to an enhancement in the chlorophyll b (Chlb) content, vital for sustaining photosynthesis processes. Furthermore, Ri's ability to enhance phosphorus (P) absorption under stressful conditions ensured a steady influx of essential nutrients. These findings point to different strategies employed for Fm and Ri inoculation. To holistically assess the saline-alkaline tolerance of each treatment group, a membership function analysis was employed, ultimately ranking the salt tolerance as Fm > Ri > non-mycorrhizal (NM) control. This finding holds paramount importance for the screening of highly resilient Lycium ruthenicum strains and offers invaluable theoretical underpinnings and technical guidance for the remediation of saline-alkaline soils, fostering sustainable agricultural practices in challenging environments.

Combined alkali-photocatalytic stimulation enables click microbial domestication for boosted ammonia nitrogen removal

Microbe-driven ammonia nitrogen removal plays a crucial role in the nitrogen cycle and wastewater treatment. However, the rational methods and mechanisms for boosting nitrogen conversion through microbial domestication are still limited. Herein, a combined alkali-photocatalytic stimulation strategy was developed to activate the Halomonas shizuishanensis DWK9 for efficient ammonia nitrogen removal. The strain DWK9 selected from saline-alkaline soil in Northwestern China possessed strong resistance to stress of saline-alkaline environment and free radicals, and was abundant in nitrogen conversion genes, thus is an ideal model for advanced microbial domestication. Bacterial in the combined alkali-photocatalytic stimulation group achieved a high ammonia nitrogen conversion rate of 67.5 %, 10 times outperforming the non-stimulated and single alkali/photocatalytic stimulation control groups. Morphology analysis revealed that the bacteria in the alkali-photocatalytic stimulated group formed a favorable structure for bioelectric transfer. Remarkably, the domesticated bacteria demonstrated improved electrochemical properties, including increased current capacity and lower overpotentials and impedance. Prokaryotic transcription genetic analysis together with qPCR analysis showed upregulation of denitrification-related metabolic pathway genes. A novel FAD dependent and NAD(P)H independent energy mode has been proposed. The universality and effectiveness of the as-developed combined alkali-photocatalytic microbial domestication strategy were further validated through indicator fish survival experiments. This work provides unprecedented degrees of freedom for the exploration of rational microbial engineering for optimized and controllable biogeochemical conversion.

Comprehensive evaluation and application of woody plants in the green spaces of parks in saline-Alkaline areas from a low-carbon perspective: A case study of Tianjin Qiaoyuan Park.

The field of landscape architecture has placed significant emphasis on low-carbon landscapes due to the increasing challenges posed by global warming and environmental deterioration in recent years. The soil ecological conditions in saline-alkaline areas are characterized by poor quality, resulting in suboptimal growth conditions for trees. This, in turn, hampers their ability to effectively sequester carbon, thereby diminishing the potential benefits of carbon sinks. Additionally, the maintenance of tree landscapes in such areas generates more carbon emissions than does conventional green land, making it difficult to reap the benefits of tree-based carbon. A comprehensive evaluation of trees in green park spaces in saline-alkaline areas is conducted from a low-carbon perspective; by identifying the dominant tree species that are well suited to greening, we can offer a precise scientific foundation for implementing low-carbon greening initiatives in cities situated in saline-alkaline environments. Therefore, as a case study, this study investigates Tianjin Qiaoyuan Park, a typical saline park in the Bohai Bay region. The hierarchical analysis method (AHP) was used to evaluate 50 species of trees and shrubs in the park from a low-carbon perspective. The results show that the evaluation system consists of four criterion layers and 15 indicator factors. The relative weight of the criterion layer followed the order of habitat adaptability (B2) > carbon sequestration capacity (B1) > low-carbon management and conservation (B3) > landscape aesthetics (B4). The indicator layer assigned greater weight values to net assimilation (C1), saline and alkaline adaptability (C3), drought tolerance (C4), irr igation and fertilization needs (C8), growth rate (C2), and adaptability to barrenness (C5). The trees were classified into five distinct categories, with each exhibiting significant variation in terms of the strengths and weaknesses of the indicators. According to the comprehensive score, the trees were categorized into three levels. The Grade I plants exhibited the best carbon efficiency performance, comprising a total of 12 species (e.g. Sabina chinensis, Fraxinus chinensis 'Aurea' and Hibiscus syriacu), and demonstrated superior performance in all aspects. Grade II trees, consisting of 26 species (e.g Pinus tabuliformis, Paulownia fortunei, Ligustrum × vicaryi), had the second-highest comprehensive score. Moreover, Grade III trees, encompassing 12 species (e.g Acer mono, Cedrus deodara, Magnolia denudata), exhibited lower comprehensive scores. The extensive use of Grade I and II tree species is recommended in the implementation of low-carbon greening projects in the Bohai Bay region, while Grade III tree species should be judiciously utilized. The findings of this research can serve as a valuable resource for the scientific identification of tree species that are suitable for urban park green spaces in the Bohai Bay region, which is characterized by predominantly saline and alkaline soil. Additionally, the development of an evaluation system can guide the selection of low-carbon tree species when evaluating other types of saline and alkaline lands.

Efficient preparation of alginate oligosaccharides by using alginate lyases and evaluation of the development promoting effects on Brassica napus L. in saline-alkali environment

Enzymatic degradation of alginate for the preparation of alginate oligosaccharides (AOS) is currently receiving significant attention in the field. AOS has been shown to promote crop growth and improve plant resistance to abiotic stresses. In this study, two PL6 family alginate lyases, AlyRmA and AlyRmB, were expressed and characterized. These enzymes demonstrate exceptional activity and stable thermophilicity compared to other known alginate lyases. AlyRmA (8855.34 U/mg) and AlyRmB (7879.44 U/mg) exhibited excellent degradation activity towards sodium alginate even at high temperatures (70 °C). The AlyRmA and AlyRmB were characterized and utilized to efficiently produce AOS. The study investigated the promotional effect of AOS on the growth of Brassica napus L. seedlings in a saline-alkaline environment. The results of this study demonstrate the high activity and thermal stability of AlyRmA and AlyRmB, highlighting their potential in the preparation of AOS. Moreover, the application of AOS prepared by AlyRmB could enhance the resistance of Brassica napus L. to saline-alkali environments, thereby broadening the potential applications of AOS.

Adaptation responses of different ecotypes of Leymus chinensis to saline–alkaline stress

IntroductionSoil salinity–alkalinity has emerged as a global problem affecting many ecosystems, including grassland. Plants evolve into different ecotypes to adapt to various environments. Leymus chinensis widely distributed in the eastern Eurasian steppe, has evolved into two main ecotypes: yellow–green(YG) and gray–green (GG). Studies on the adaption mechanisms of both ecotypes in response to saline–alkaline stress are limited.MethodsIn this study, the growth and physiological traits of ecotypes YG and GG in soils with different salinity–alkalinity levels—severe saline–alkaline soil (SS), moderate saline–alkaline soil (MS), and light saline–alkaline soil (LS)—were studied. After exposure to saline–alkaline stress for 15 months, the L. chinensis ecotypes exhibited significant differences in the growth characteristics.ResultsThe specific leaf area, individual tiller biomass, net photosynthetic rate, and potassium content of the two ecotypes under MS conditions were significantly higher than or similar to those under LS conditions. This indicates that L. chinensis showed a certain degree of tolerance to saline–alkaline environments under MS conditions. Saline–alkaline stress increased the tillers by 56% in GG and reduced them by 26% in YG, and did not alter the SLA and the number of individual tiller leaves of GG but reduced that of YG. Moreover, with increasing levels of saline–alkaline stress, ecotype GG exhibited an increase in net photosynthetic rate (Pn), while ecotype YG showed insignificant changes. Under SS, GG exhibited higher Pn and chlorophyll content than YG. Additionally, with the increase in the saline–alkaline stress level, the Na+ content increased, but GG exhibited a significantly lower Na+ content than YG. Conversely, the K+ and Ca2+ contents and the K+/Na+ and Ca2+/Na+ ratios decreased, but GG exhibited higher values than YG.DiscussionGG reduced Na+ by absorption by increasing tillers. Additionally, GG absorbed more K+ and Ca2+ ions, thereby maintaining higher K+/Na+ and Ca2+/Na+ ratios than YG under saline–alkaline stress. These adaptive strategies enable ecotype GG to grow and maintain normal physiological functions under high saline–alkaline stress. The findings of this study hold practical significance for enhancing the economic and ecological value of saline–alkaline grasslands.

Enhancement of Nutrient Composition and Non-Volatile Flavor Substances in Muscle Tissue of Red Drum (Sciaenops ocellatus) Through Inland Low Salinity Saline-Alkaline Water Culture.

The red drum (Sciaenops ocellatus), a globally significant marine aquaculture species, boasts formidable osmoregulatory capabilities and remarkable adaptability to low salinity, making it an ideal candidate for commercial cultivation in inland low salinity saline-alkaline waters. However, studies on the fundamental nutritional composition and flavor quality of S. ocellatus in these inland low salinity saline-alkaline waters remain unreported. This study delves into the impact of inland low salinity saline-alkaline environments on the basic nutritional components and nonvolatile flavor substances (including free amino acids and free nucleotides) in the muscle tissue of S. ocellatus. The findings reveal that redfish cultivated in these conditions exhibit a significant increase in the crude fat, ash, and protein content in their dorsal muscle tissue, coupled with a decrease in moisture content (p < 0.05), indicating an enhancement in the nutritional value of the dorsal muscle tissue. Furthermore, this cultivation environment significantly elevates the content of free amino acids in the muscle tissue (p < 0.05), particularly those contributing to umami and sweet tastes, while reducing the relative content of bitter amino acids. Although the total content of free nucleotides decreased, the equivalent umami concentration (EUC) in the muscle tissue markedly increased (p < 0.05) due to the synergistic effect of umami amino acids and flavor nucleotides, enhancing the umami taste characteristics. Therefore, inland low salinity saline-alkaline aquaculture not only elevates the nutritional value of S. ocellatus muscle tissue but also improves its umami flavor characteristics. This discovery opens new perspectives for further research into the impact of inland low salinity saline-alkaline environments on the flavor properties of marine animals.

Potassium transporter OsHAK17 may contribute to saline-alkaline tolerant mechanisms in rice (Oryza sativa).

Rice production is seriously affected by saline-alkaline stress worldwide. To elucidate the saline-alkaline tolerance mechanisms in a novel tolerant rice variety, Shwe Nang Gyi (SNG), we investigated ion accumulation in SNG and Koshihikari (KSH), which is a saline-alkaline sensitive rice variety, and the candidates for saline-alkaline inducible genes in SNG using RNA-seq. SNG had superior ion accumulation capacity, such as K and Zn, compared to KSH. In contrast, SNG accumulated the same level of Na content in its leaf blades as KSH despite the higher dry weight of the SNG leaf blades. We further found that the expression of numerous genes, including several K+ transporter/high-affinity K+ transporter/K+ uptake protein/K+ transporter (HAK/KUP/KT) family members, were upregulated in SNG, and that OsHAK17 and OsHAK21 expression levels in the roots were significantly higher in SNG than in KSH. Moreover, yeast complementation analysis revealed that OsHAK17 was involved in K+ uptake under high-Na conditions. These results suggested that SNG has an effective K+ acquisition system supported by OsHAK17 functioning in saline-alkaline environments.

The bidirectional extracellular electron transfer process aids iron cycling by Geoalkalibacter halelectricus in a highly saline-alkaline condition.

Bidirectional extracellular electron transfer (EET) is crucial to upholding microbial metabolism with insoluble electron acceptors or donors in anoxic environments. Investigating bidirectional EET-capable microorganisms is desired to understand the cell-cell and microbe-mineral interactions and their role in mineral cycling besides leveraging their energy generation and conversion, biosensing, and bio-battery applications. Here, we report on iron cycling by haloalkaliphilic Geoalkalibacter halelectricus via bidirectional EET under haloalkaline conditions. It efficiently reduces Fe3+ oxide (Fe2O3) to Fe0 at a 0.75 ± 0.08 mM/mgprotein/d rate linked to acetate oxidation via outward EET and oxidizes Fe0 to Fe3+ at a 0.24 ± 0.03 mM/mgprotein/d rate via inward EET to reduce fumarate. Bioelectrochemical cultivation confirmed its outward and inward EET capabilities. It produced 895 ± 23 µA/cm2 current by linking acetate oxidation to anode reduction via outward EET and reduced fumarate by drawing electrons from the cathode (‒2.5 ± 0.3 µA/cm2) via inward EET. The cyclic voltammograms of G. halelectricus biofilms revealed redox moieties with different formal potentials, suggesting the involvement of different membrane components in bidirectional EET. The cyclic voltammetry and GC-MS analysis of the cell-free spent medium revealed the lack of soluble redox mediators, suggesting direct electron transfer by G. halelecctricus in achieving bidirectional EET. By reporting on the first haloalkaliphilic bacterium capable of oxidizing and reducing insoluble Fe0 and Fe3+ oxide, respectively, this study advances the limited understanding of the metabolic capabilities of extremophiles to respire on insoluble electron acceptors or donors via bidirectional EET and invokes the possible role of G. halelectricus in iron cycling in barely studied haloalkaline environments. IMPORTANCE Bidirectional extracellular electron transfer (EET) appears to be a key microbial metabolic process in anoxic environments that are depleted in soluble electron donor and acceptor molecules. Though it is an ecologically important and applied microbial phenomenon, it has been reported with a few microorganisms, mostly from nonextreme environments. Moreover, direct electron transfer-based bidirectional EET is studied for very few microorganisms with electrodes in engineered systems and barely with the natural insoluble electron acceptor and donor molecules in anoxic conditions. This study advances the understanding of extremophilic microbial taxa capable of bidirectional EET and its role in barely investigated Fe cycling in highly saline-alkaline environments. It also offers research opportunities for understanding the membrane components involved in the bidirectional EET of G. halelectricus. The high rate of Fe3+ oxide reduction activity by G. halelectricus suggests its possible use as a biocatalyst in the anaerobic iron bioleaching process under neutral-alkaline pH conditions.

Micromonospora profundi TRM 95458 converts glycerol to a new osmotic compound.

Plant growth and agricultural productivity was greatly limited by soil salinity and alkalization. The application of salt-tolerant rhizobacteria could effectively improve plant tolerance to saline-alkali stress. Micromonospora profundi TRM 95458 was obtained from the rhizosphere of chickpea (Cicer arietinum L.) as a moderate salt-tolerant rhizobacteria. A new osmotic compound (ABAGG) was isolated from the fermentation broth of M. profundi TRM 95458. The chemical structure of the new compound was elucidated by analyzing nuclear magnetic resonance (NMR) and high-resolution mass (HRMS) data. M. profundi TRM 95458 could convert glycerol into ABAGG. The accumulation of ABAGG varied depending on the amount of glycerol and glycine added to the fermentation medium. In addition, the concentration of NaCl affected the ABAGG content obviously. The highest yield of ABAGG was observed when the salt content of the fermentation medium was 10 g/L. The study indicated that salt stress led to the accumulation of ABAGG using glycerol and glycine as substrates, suggesting ABAGG might aid in the survival and adaptation of the strain in saline-alkaline environments as a new osmotic compound.

Halving gypsum dose by Penicillium oxalicum on alkaline neutralization and microbial community reconstruction in bauxite residue

Bauxite residue is a high-alkaline solid waste generated during alumina production, which greatly limits the growth of soil microorganisms and plants. Here, we developed a novel integrated approach to stabilize alkalinity and reduce the dose of Ca-contained solid waste by inoculation with alkali-tolerant and acid-producing microorganisms. The integrated application of Penicillium oxalicum (P. oxalicum) and gypsum maintained pH at about 9.0 and reduced the dose of gypsum to 2% compared to 4% (w/w) gypsum. Alkaline mineral transformation and organic components conversion in the solid and liquid phases of residues by XRD, XPS, SEM-EDS, FT-IR, and spectroscopic technology demonstrated that P. oxalicum could alleviate extreme saline-alkaline environment by the secreting of carboxylic acids (e.g., oxalic acid) and continuously neutralizing the alkalinity. The ternary plots obtained by high-throughput sequencing revealed that the excessive exogenous ameliorants enhanced the metabolic burden of microorganisms and changed the community assembly processes. Inoculation with P. oxalicum enriched microbial taxa, including Pseudomonas, Alkalibacterium, P. oxalicum, and Epicoccum nigrum, which may also drive a greater response of opportunistic taxa throughout the biomes during amelioration. Overall, the results of the study provided an eco-friendly strategy for alkaline regulation and secondary risk control by the integrated application of functional microorganisms and solid wastes prior to ecological rehabilitation. This work will enhance the understanding of de-alkalization in bauxite residue and demonstrate the application potential of functional microorganisms in ecological reconstruction at disposal areas.

Macroevolutionary trends and diversification dynamics in Atripliceae (Amaranthaceae s.l., Chenopodioideae): a first approach.

Atripliceae evolved and diversified by dispersals and radiations across continents in both hemispheres, colonizing similar semi-arid, saline-alkaline environments throughout the world. Meanwhile, its species developed different life forms, photosynthetic pathways, mono- or dioecy, and different morphological features in flowers, fruiting bracteoles and seeds. In this study, we introduce a first approach to the macroevolutionary patterns and diversification dynamics of the Atripliceae to understand how time, traits, speciation, extinction and new habitats influenced the evolution of this lineage. We performed molecular phylogenetic analyses and clade age estimation of Atripliceae to apply time-, trait- and geographic-dependent diversification analyses and ancestral state reconstructions to explore diversification patterns within the tribe. Opposite diversification dynamics within the two major clades of Atripliceae, the Archiatriplex and Atriplex clades, could explain the unbalanced species richness between them; we found low mean speciation rates in the Archiatriplex clade and one shift to higher speciation rates placed in the branch of the Atriplex core. This acceleration in diversification seems to have started before the transition between C3 and C4 metabolism and before the arrival of Atriplex in the Americas, and matches the Mid-Miocene Climatic Optimum. Besides, the American species of Atriplex exhibit slightly higher net diversification rates than the Australian and Eurasian ones. While time seems not to be associated with diversification, traits such as life form, photosynthetic pathway and plant sex may have played roles as diversification drivers. Traits more than time played a key role in Atripliceae diversification, and we could speculate that climate changes could have triggered speciation. The extreme arid or saline environments where Atripliceae species prevail may explain its particular evolutionary trends and trait correlations compared with other angiosperms and highlight the importance of conservation efforts needed to preserve them as genetic resources to deal with climatic changes.

Analysis of spatial distribution pattern and its influencing factors of the Tamarix chinensis population on the beach of the muddy coastal zone of Bohai Bay

To explore the spatial distribution pattern of the Tamarix chinensis population and the influencing factors in the muddy coastal zone of Bohai Bay, we studied the T. chinensis forest on the beach of the muddy area of Beihai New District, Binzhou City, Shandong Province. A combination of field investigations and laboratory-based sample analyses were used to measure and analyze the forest density, height, cover, distance from the sea, groundwater depth, soil salinity, basic soil physical properties and soil nutrients. The results showed that the coefficients of variation for the 18 soil and forest indices for T. chinensis were between 0.03 and 0.96; the coefficients of variation for forest density, soil Ca2+ and Na+ content were the greatest, followed by those for soil Mg2+, soil salt content, distance from sea, and available phosphorus, while those for soil bulk density, total phosphorus, pH and other indicators changed less. The population of T. chinensis on the beach of the coastal zone of the Yellow River Delta showed an aggregated distribution, and its aggregation intensity decreased with increasing spatial scale, and it tended to evolve into a random distribution on a larger scale. The spatial distribution of the T. chinensis population showed a certain density dependence; that is, the greater the density was, the greater the aggregation intensity. The reason for the aggregated distribution of the T. chinensis population was mainly related to the biological characteristics of the organism itself or to the interactions between its biological characteristics and environmental factors. T. chinensis forest density was significantly and negatively correlated with organic carbon, total phosphorus, Ca2+, and Na+ (P < 0.05) and very significantly and negatively correlated with available phosphorus (P < 0.01). The soil water content was significantly and positively correlated with the soil salt content, K+, and Na+ (P < 0.01) and significantly and negatively correlated with the distance from the sea and groundwater depth (P < 0.05). The soil salt content was significantly and positively correlated with K+, Na+, and nitrate nitrogen (P < 0.01) and significantly and negatively correlated with distance from the sea and groundwater depth (P < 0.05). K+ and Na+ were the main cations contributing to soil salinity in this T. chinensis forest. With an increase in the distance from the sea, the groundwater depth and forest density gradually increased, and the soil water content and soil salt content gradually decreased. Soil water content, soil salt content, K+, and Na+ content were the dominant factors affecting the spatial distribution pattern for the T. chinensis population in the coastal tidal flat of the Yellow River Delta, followed by organic carbon, ammonia nitrogen, and finally the Mg2+, SO42-, Cl- content, and distance from the sea. The population distribution pattern for T. chinensis was mainly affected by the water and salt conditions, which is a result of the long-term adaptation and evolution of the species within the coastal saline-alkaline environment. Therefore, in the planting management and protection of T. chinensis in the muddy coastal zone of Bohai Bay, we should try to maintain the aggregation growth characteristics of the population according to the adaptation mechanism and biological characteristics of different habitats and community types of T. chinensis, allowing other species to coexist with T. chinensis, and thus optimizing the habitat in the coastal zone.

Effects of saline-alkali stress on bacterial and fungal community diversity in Leymus chinensis rhizosphere soil.

The salinization of grassland in arid and semi-arid areas is a serious environmental issue in China. Halophytes show extreme salt tolerance and are grown in saline-alkaline environments. Their rhizosphere microorganisms contribute significantly to plant stress tolerance. To study bacterial and fungal community structure changes in Chinese ryegrass (Leymus chinensis) rhizosphere soil under salt and alkali stress, pot experiments were conducted with different salt and alkali stress intensities. High-throughput sequencing was conducted, and the microbial diversity, community structure, and driving factors were analyzed in rhizosphere soil. The salinization of grassland in arid and semi-arid areas is a serious environmental issue in China. Halophytes show extreme salt tolerance and grow in saline-alkaline environments. A total of 549 species of bacteria from 28 phyla and 250 species from 11 phyla of fungi were detected in the rhizosphere soil of Leymus chinensis with different saline-alkali gradients. Alpha diversity analysis along saline-alkali gradients showed that bacterial community richness and diversity were the highest in the moderate saline-alkali group (pH = 8.28, EC = 160.4 μS·cm-1), while fungi had high richness and diversity in the control group (pH = 7.35, EC = 134.5 μS·cm-1). The bacteriophyta Proteobacteria, Acidobacteria, Plantomycetes, and the eumycota Ascomycota, Basidiomycota, and Glomeromycota were found with relative abundances of more than 10%. Saline-alkali gradients had significant effects on the abundance of the bacterial and fungal groups in the rhizosphere. The distribution of bacterial colony structure was not significant at the species level (P > 0.05). However, there were significant differences in the distribution of fungal structure and considerable differences in the composition of fungal species among the moderate saline-alkali group, severe saline-alkali group, and control group (P < 0.05). Correlation analysis showed that the bacterial phylum Gemmatimonadetes had a highly significant positive correlation with pH and EC (P < 0. 01). Saline-alkali stress significantly inhibited the abundance of the bacteria Latescibacteria, Cyanobacteria, and Bacteroides, and the fungi Zoopagomycota, Mortierllomycota, and Cryptomycota (P < 0. 05). Compared with fungi, bacterial community composition was most closely correlated with soil salinization. This report provided new insights into the responses of relationships between rhizosphere soil microorganisms and salt and alkali tolerance of plants.

Biodiversity of wild Lactococcus lactis and their geo-spatial relationship with the environment.

Lactic acid bacteria are distributed in nature, isolating themselves from diverse ecosystems and presenting a wide metabolic biodiversity. In Corrientes (Argentina), artisanal cheeses and their specific environment are an important source of autochthonous lactic acid bacteria. The objective of this work was to establish associations between the phenotypic characteristics of strains of Lactococcus lactis subsp. lactis native from Corrientes with climatological data of the Province and the characteristics of the soil and the landscapes. Physiological and biochemical characterization data of Lactococcus lactis subsp. lactis isolated from the dairy environment and from different localities of Corrientes will be used. The strains were space-located through Google Earth, flood and drought events were evaluated using Standardized Precipitation Evapotranspiration Index, and soil composition data (A and Bt horizons) in the study areas were obtained from the experimental station National Institute of Agricultural Technology - Corrientes. A statistical analysis was applied to these results (Infostat Software, Di Rienzo et al. 2008). The resulting consists in three conglomerates, differentiating strains from soils coming from "flooded landscapes" and those from "sandy hills landscape". The analysis by main components highlighted the preference of strains from flooded landscapes by a saline-alkaline environment, affecting during periods of drought, and strains from sandy hills landscape by a low medium in salts and acid soil, directly during period of high humidity resulting from previous floods.

Rhizosphere bacteria community and functions under typical natural halophyte communities in North China salinized areas.

Soil salinity is a serious environmental issue in arid China. Halophytes show extreme salt tolerance and are grow in saline-alkaline environments. There rhizosphere have complex bacterial communities, which mediate a variety of interactions between plants and soil. High-throughput sequencing was used to investigated rhizosphere bacterial community changes under the typical halophyte species in arid China. Three typical halophytes were Leymus chinensis (LC), Puccinellia tenuiflora (PT), Suaeda glauca (SG). The dominant phyla were Proteobacteria, Actinobacteria, Chloroflexi, Gemmatimonadetes, Acidobacteria and Bacteroidetes, Suaeda glauca rhizosphere has stronger enrichment of Nitrospirae and Cyanobacteria. The Ace, Chao and Shannon indices were significantly higher in soils under LC and SG (P<0.05). Functional predictions, based on 16S rRNA gene by PICRUSt, indicated that Energy metabolism, Amino acid metabolism, Carbohydrate metabolism and Fatty acid metabolism are dominant bacterial functions in three halophytes rhizosphere soil. Carbon metabolism, Oxidative phosphorylation, Methane metabolism, Sulfur metabolism and Nitrogen metabolism in SG were significantly higher than that in LC and PT. Regression analysis revealed that rhizosphere soil bacterial community structure is influenced by soil organic matter (SOM) and soil water content (SWC), while soil bacterial community diversity is affected by soil pH. This study contributes to our understanding of the distribution characteristics and metabolic functions under different halophyte rhizosphere bacterial communities, and will provide references for the use of rhizosphere bacteria to regulate the growth of halophytes and ecological restoration of saline soil.

Transverse low-velocity impact performance of BFRP bars after exposure to the saline-alkaline environment

The saline environment is one of the most severe exposure conditions for infrastructure due to its corrosive nature. Fiber reinforcement polymer (FRP) bars are being considered as a replacement for steel rebars to prevent corrosion. However, the effects of saline environments and alkaline cementitious conditions on the impact performance of FRP bars are not well known. Therefore, this study aims at examining the low-velocity impact performance of basalt FRP (BFRP) bars after exposure to the saline-alkaline environment for 24, 48, and 72 days and elevated temperatures (25, 40, and 55 °C). The maximum load-bearing capacity, deformation capacity, and energy absorption capacity of the deteriorated BFRP bars are measured. Environmental scanning electron microscope (ESEM) and Fourier transform infrared spectroscopy (FTIR) were used to study the deterioration mechanism further. It was revealed that both the fracture threshold and the bending stiffness of BFRP bars generally decrease with the elevated exposure temperature and duration. The findings also suggest that deterioration of BFRP bars in a natural saline-alkaline environment is less severe than the simulated saline-alkaline solution. This study provides some insights to promote the application of FRP composites in coastal and marine structures in a saline-alkaline environment with low-velocity impact loads.

Effects of SLC protein on intestinal HCO&amp;lt;sup&amp;gt;-&amp;lt;/sup&amp;gt;&amp;lt;sub&amp;gt;3&amp;lt;/sub&amp;gt; excretion and acid-base balance of &amp;lt;italic&amp;gt;Gymnocypris przewalskii&amp;lt;/italic&amp;gt;

Saline-alkaline water, widely distributed throughout China, is characterized as high salinity and alkalinity, which are the primary factors restricting the survival and growth of aquatic organisms. The physiological mechanisms required for fish to live in fresh water and sea water are well described for several species. Many fishes not only can tolerate, but also can acclimate and adapt to conditions besides conventional fresh water and sea water conditions, specifically saline-alkaline water. When fishes are transferred to saline-alkaline water, there is a transient alkalosis with increased HCO^-₃ or decreased <italic>P</italic>_CO₂ concentrations in the plasma. <italic>Gymnocypris przewalskii</italic> is the most important economic fish in Lake Qinghai, a water body with high salinity and alkalinity. In recent years, the population of <italic>G</italic>. <italic>przewalskii</italic> has sharply declined due to the destruction of spawning habitat, long-term overfishing and the increasing salinity and alkalinity. Thus, researches on the physiological and molecular responses of <italic>G</italic>.<italic>przewalskii</italic> under saline-alkaline conditions are significant for recovering this endangered species. Previous studies had shown that, when <italic>G</italic>. <italic>przewalskii</italic> was acclimated to saline-alkaline water, internal excess HCO^-₃ was not totally excreted by the gills or the kidney. In contrast, it showed that intestinal HCO^-₃ secretion and water absorption might play important roles in the acid-base balance and osmoregulation. In order to explore the effects of SLC protein on intestinal HCO^-₃ excretion and acid-base regulation, <italic>Gymnocypris przewalskii</italic> was exposed to fresh water and saline-alkaline lake water treatments. 4,4′-diisothiocyanatostilbene-2,2′-disulfonic acid disodium salt hydrate (DIDS) was injected to control the activity of SLC protein, the intestinal HCO^-₃ excretion concentration, blood physiological indices, and the relative expression of <italic>SLC</italic>4<italic>A</italic>1, <italic>SLC</italic>4<italic>A</italic>2, <italic>SLC</italic>4<italic>A</italic>4, <italic>SLC</italic>26<italic>A</italic>6 genes in the intestine of <italic>Gymnocypris przewalskii</italic> were detected. Results showed that under saline-alkaline environment, the blood pH of <italic>Gymnocypris przewalskii</italic> increased significantly, while the <italic>P</italic>_CO₂ decreased, the concentration of intestinal HCO^-₃ excretion and the expression levels of <italic>SLC</italic>4<italic>A</italic>1, <italic>SLC</italic>4<italic>A</italic>4, and <italic>SLC</italic>26<italic>A</italic>6 genes increased significantly. After the injection of DIDS, the blood pH and HCO^-₃ concentration of <italic>Gymnocypris przewalskii</italic> in the fresh water group increased significantly while <italic>P</italic>_CO₂ decreased; in saline-alkaline water group, the blood pH and HCO^-₃ concentration of <italic>Gymnocypris przewalskii</italic> increased significantly, and the intestinal HCO^-₃ excretion concentration declined. Results indicated that <italic>Gymnocypris przewalskii</italic> intestinal HCO^-₃ excretion in saline-alkaline environment increased, but the excretion declined with the inhibition of SLC family proteins, leading to blood pH increase and acid-base imbalance. This study indicate that the SLC family protein may play a compensatory role in the adaptation of <italic>Gymnocypris przewalskii</italic> to high saline-alkaline environment.