Saline-alkaline Water Research Articles

Proline metabolism is essential for alkaline adaptation of Nile tilapia (Oreochromis niloticus)

BackgroundSaline-alkaline water aquaculture has become a key way to mitigate the reduction of freshwater aquaculture space and meet the increasing global demand for aquatic products. To enhance the comprehensive utilization capability of saline-alkaline water, it is necessary to understand the regulatory mechanisms of aquatic animals coping with saline-alkaline water. In this study, our objective was to elucidate the function of proline metabolism in the alkaline adaptation of Nile tilapia (Oreochromis niloticus).ResultsExpose Nile tilapia to alkaline water of different alkalinity for 2 weeks to observe changes in its growth performance and proline metabolism. Meanwhile, to further clarify the role of proline metabolism, RNA interference experiments were conducted to disrupt the normal operation of proline metabolic axis by knocking down pycr (pyrroline-5-carboxylate reductases), the final rate-limiting enzyme in proline synthesis. The results showed that both the synthesis and degradation of proline were enhanced under carbonate alkalinity stress, and the environmental alkalinity impaired the growth performance of tilapia, and the higher the alkalinity, the greater the impairment. Moreover, environmental alkalinity caused oxidative stress in tilapia, enhanced ion transport, ammonia metabolism, and altered the intensity and form of energy metabolism in tilapia. When the expression level of the pycr gene decreased, the proline metabolism could not operate normally, and the ion transport, antioxidant defense system, and energy metabolism were severely damaged, ultimately leading to liver damage and a decreased survival rate of tilapia under alkalinity stress.ConclusionsThe results indicated that proline metabolism plays an important role in the alkaline adaptation of Nile tilapia and is a key regulatory process in various biochemical and physiological processes.

Physiological and molecular responses of juvenile silver crucian carp (Carassius gibelio) to long-term high alkaline stress: Growth performance, histopathology, and transcriptomic analysis

Salty-alkaline waters are widely distributed globally, and how to effectively develop saline-alkaline water to improve the utilization rate of water resources has become a global challenge. This study examined the survival performance of juvenile silver crucian carp (Carassius gibelio) under alkaline gradient acclimation conditions and explored the regulatory mechanisms for their adaptation to high alkalinity. Compared to directly immersing in high concentrations, alkaline gradient acclimation significantly improved the survival rate of juvenile silver crucian carp. Long-term high alkaline stress caused significant reduction in the growth performance of juvenile silver crucian carp. After alkaline stress, the enzyme activities of Na+-K+-ATP (NKA) and Ca2+-Mg2+-ATP (CMA) in the gills were significantly decreased. Meanwhile, histopathology of the gills showed structural changes, indicating that the physiological functions of juvenile silver crucian carp were impaired under alkaline conditions. Transcriptomic analysis found that the expression of genes related to metabolism and immune response pathways in the gill and kidney underwent significant changes. Genes related to carbohydrate metabolism were upregulated while those related to protein metabolism were downregulated, indicating that alkaline stress caused the organism to utilize carbohydrates rather than proteins as much as possible to meet enhanced metabolism. The HIF pathway that maintains the body's survival was significantly up-regulated, at the expense of high energy consumption. Dysregulation of genes related to the formation of neutrophil extracellular traps (NETosis) pathway indicated that the immune function of the fish was suppressed. Overall, this study revealed the physiological and molecular responses of juvenile silver crucian carp to alkaline stress, deepening our understanding of their adaptation strategies and the potential impact of alkaline environments on aquatic life.

Effects of bicarbonate on antioxidant, immune, osmolytic and metabolic capabilities of Scylla paramamosain

The world is rich in saline-alkali water resources, and the effective utilization of saline-alkali water resources is of great significance to the promotion of human economic development. This study investigated the effects of carbonate saline water on the immune, antioxidant, osmotic regulatory, and metabolic capacities of S. paramamosain. Bicarbonate stress resulted in damage to the hepatopancreas, as well as significantly upregulating the activities of superoxide dismutase and catalase, indicating that the antioxidant capacity increased under short-term bicarbonate stress, but then decreased. Long-term bicarbonate stress caused further oxidative damage. The activities of alkaline phosphatase and acid phosphatase also significantly increased, indicating an initially enhanced immune response of S. paramamosain to carbonate salinity stress that then declined, suggesting that the ability to mount an immune response decreased following long-term exposure. High bicarbonate levels also significantly inhibited the osmotic regulation ability of S. paramamosain, and negatively impacted metabolic indexes (e.g., glucose, total cholesterol, triglycerides, urea nitrogen, and uric acid). Three groups of metabolites were differentially upregulated and 95 were differentially downregulated, including ‘organooxygen compounds’, ‘carboxylic acids and derivatives’, ‘fatty acyls’, ‘glycerophospholipids’ and ‘keto acids and derivatives’. Thus, long-term bicarbonate stress also decreased energy metabolism in S. paramamosain. Under long-term bicarbonate stress, related products of energy metabolism were significantly downregulated, and bicarbonate stress significantly inhibited energy uptake in S. paramamosain. This study analyzed the stress mechanism of bicarbonate on S. paramamosain, further enriched the culture theory of S. paramamosain, in order to provide a theoretical basis for the improvement of saline-alkaline water culture technology of S. paramamosain.

Physiological Adaptation of Fenneropenaeus chinensis in Response to Saline-Alkaline Stress Revealed by a Combined Proteomics and Metabolomics Method.

The rapid development of the mariculture industry has been hindered by limited coastal aquaculture space. To utilize the abundant inland saline-alkaline water, we studied the physiological effects of high carbonate alkalinity stress and high pH stress on Fenneropenaeus chinensis. The study employed quantitative proteomics by tandem mass tag (TMT) and non-targeted metabolomics analysis using a liquid chromatograph mass spectrometer (LC-MS) to understand the physiological and biochemical adaptive mechanisms of the hepatopancreas of F. chinensis in response to saline-alkaline stress at the molecular level. We designed two stress groups as follows: a high carbonate alkalinity (CA) group and a combined high carbonate alkalinity and high pH (CP) group. The study found that the protein and metabolic profiles of the two stress groups were changed, and the CP group, which was exposed to dual stresses, incurred more severe damage to the hepatopancreas compared to that of the CA group. After exposure to CA and CP, the hepatopancreas of F. chinensis showed significant alterations in 455 proteins and 50 metabolites, and 1988 proteins and 272 metabolites, respectively. In addition, F. chinensis upregulated the level of energy metabolism in the hepatopancreas to defend against osmotic imbalance caused by CA or CP stress, which was demonstrated by the significant upregulation of important proteins and metabolites in glycolysis, pyruvate metabolism, TCA cycle, and fatty acid oxidation. Additionally, pattern recognition receptors, the phenol oxidase system, and various immune-related metabolic enzymes and metabolites were also affected. The immune homeostasis of F. chinensis was affected by the alteration of the antioxidant system following exposure to CA or CP. These findings provide valuable information for F. chinensis saline-alkaline water cultivation practices.

Transcriptomic and histologic analyses preliminarily reveal the immune-metabolic response mechanism to saline-alkaline in large yellow croaker (Larimichthys crocea)

There are large areas of saline-alkaline waters worldwide, the utilization of which would greatly enhance the development of aquaculture productivity. To elucidate the regulatory mechanisms underlying the adaptation of large yellow croaker (Larimichthys crocea) to saline-alkaline water, this study analyzed the growth performance, tissue histology, and gills transcriptome profiles of L. crocea in both seawater (CK) and saline-alkaline water (EX) groups. Growth indices statistics revealed that L. crocea can adapt to saline-alkaline water, with growth performance comparable to that of the CK group. Histological examination revealed partial cellular detachment and structural relaxation in the gills tissue of the EX group, while liver and kidney tissues appeared normal. Transcriptome analysis revealed 3821 differentially expressed genes (DEGs), with 1541 DEGs up-regulated and 2280 DEGs down-regulated. GO enrichment analysis indicated that up-regulated DEGs were enriched in terms related to metabolite production during biological activities, while down-regulated DEGs were associated with terms related to maintaining cellular activities. KEGG enrichment analysis revealed that up-regulated DEGs were enriched in pathways related to the synthesis and metabolism of amino acids and lipids, such as the PPAR signaling pathway and glutathione metabolism. The down-regulated DEGs were predominantly enriched in immune-related signaling pathways, including the Toll-like receptor signaling pathway and NOD-like receptor signaling pathway. Further analysis revealed that genes such as lipoprotein lipase A (lpla), branched-chain amino acid aminotransferase 2 (bcat2), interleukin 8 (il8), interleukin 10 (il10), and interferon regulatory factor 7 (irf7) were involved in the adaptation of L. crocea to saline-alkaline water culture conditions. This study provides a basis for understanding the adaptability of large yellow croaker to saline-alkaline water and lays the foundation for the rational utilization of fishery water resources.

The tricarboxylic acid cycle is inhibited under acute stress from carbonate alkalinity in the gills of Eriocheir sinensis

Owing to population growth and environmental pollution, freshwater aquaculture has been rapidly shrinking in recent years. Aquaculture in saline-alkaline waters is a crucial strategy to meet the increasing demand for aquatic products. The Chinese mitten crab is an important economic food in China, but the molecular mechanism by which it tolerates carbonate alkalinity (CA) in water remains unclear. Here, we found that enzyme activities of the tricarboxylic acid (TCA) cycle in the gills, such as citrate synthase, isocitrate dehydrogenase, α-ketoglutarate dehydrogenase, and malate dehydrogenase, were markedly reduced under CA stress induced by 40 mM NaHCO3. Secondly, the TCA cycle in the gills is inhibited under acute CA stress, according to proteomic and metabolomic analyses. The expressions of six enzymes, namely aconitate hydratase, isocitrate dehydrogenase, 2-oxoglutarate dehydrogenase, dihydrolipoyl dehydrogenase, succinate-CoA ligase, and malate dehydrogenase, were downregulated, resulting in the accumulation of phosphoenolpyruvic acid, citric acid, cis-aconitate, and α-ketoglutaric acid. Finally, we testified that if the TCA cycle is disturbed by malonate, the survival rate increases in CA water. To our knowledge, this is the first study to show that the TCA cycle in the gills is inhibited under CA stress. Overall, the results provide new insights into the molecular mechanism of tolerance to saline-alkaline water in crabs, which helped us expand the area for freshwater aquaculture and comprehensively understand the physiological characteristics of crab migration.

Temporal Transcriptomic Profiling Reveals Dynamic Changes in Gene Expression of Giant Freshwater Prawn upon Acute Saline-Alkaline Stresses.

Bicarbonate and sulfate are among two primary ion constituents of saline-alkaline water, with excessive levels potentially causing metabolic disorders in crustaceans, affecting their molting and interrupting development. As an economically important crustacean species, the molecular adaptive mechanism of giant freshwater prawn Macrobrachium rosenbergii in response to the stress of bicarbonate and sulfate remains unexplored. To investigate the mechanism underlying NaHCO3, Na2SO4, and mixed NaHCO3, Na2SO4 stresses, M. rosenbergii larvae were exposed to the above three stress conditions, followed by total RNA extraction and high-throughput sequencing at eight distinct time points (0, 4, 8, 12, 24, 48, 72, and 96h). Subsequent analysis revealed 13, 16, and 13 consistently identified differentially expressed genes (DEGs) across eight time points under three stress conditions. These consistently identified DEGs were significantly involved in the Gene Ontology (GO) terms of chitin-based cuticle development, protein-carbohydrate complex, structural constituent of cuticle, carnitine biosynthetic process, extracellular matrix, and polysaccharide catabolic process, indicating that alkaline stresses might potentially impact the energy metabolism, growth, and molting of M. rosenbergii larvae. Particularly, the transcriptome data revealed that DEGs associated with energy metabolism, immunity, and amino acid metabolism were enriched across multiple time points under three stress conditions. These DEGs are linked to Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways, including glycolysis/glucogenesis, amino sugar and nucleotide sugar metabolism, and lysine degradation. Consistent enrichment findings across the three stress conditions support conclusions above. Together, these insights are instrumental in enhancing our understanding of the molecular mechanisms underlying the alkaline response in M. rosenbergii larvae. Additionally, they offer valuable perspectives on the regulatory mechanisms of freshwater crustaceans amid saline-alkaline water development.

Effects of saline and alkaline stresses on the survival, growth, and physiological responses in juvenile mandarin fish (Siniperca chuatsi)

Saline-alkaline water is widely distributed and abundant worldwide. It plays a critical role in the advancement of the aquaculture and the comprehensive utilization of saline-alkaline resources. The mandarin fish (Siniperca chuatsi), a freshwater species with high economic value, and has potential for cultivation in such environments. We evaluated its tolerance to acute salinity and alkalinity, and investigated the growth and physiological changes under chronic saline and alkaline stress. Initially, the effects of acute salinity and alkalinity were estimated on mandarin fish (4.33 ± 0.31 g), and found that the LC50 for 96 h of salinity and alkalinity was 13.91 ppt and 13.45 mmol/L, respectively. Subsequently, over a 60-day period, we measured the survival, growth performance, and physiological responses in mandarin fish (22.53 ± 0.60 g) reared in freshwater (FW, the control group), saline water (SW; fixed salinity of 5 ppt) and alkaline water (AW; carbonate alkalinity of 8 mmol/L). The results indicated that neither SW nor AW group adversely affected survival rates, and growth performance in SW group was significantly superior to the FW group. Additionally, compared to the FW group， the AW group had a lower hepatosomatic index, while the SW group exhibited significantly higher meat content. In terms of physiological responses, the AW group showed elevated V-H+-ATPase (VHA) activity, whereas the SW group had decreased prolactin (PRL) levels. Furthermore, the mitochondria-rich cells (MRCs) in mandarin fish underwent morphological adaptations to saline and alkaline stress, indicating their role in osmoregulation and acid-base balance. Our results suggested that the mandarin fish demonstrated good tolerance to both salinity and alkalinity, indicating suitability for breeding in low saline and alkaline water. This research contributes to a broader understanding of saline and alkaline tolerance in aquaculture species and provides theoretical support for the cultivation of mandarin fish in saline-alkaline water. Moreover, the results of this study suggested that saline-alkaline areas and agricultural irrigation water in the world could be successfully utilized for sustainable aquaculture.

Effects of Fishery Utilization on the Physicochemical Index and Microbial Community Composition in Saline-Alkaline Water.

Fishery utilization of idle saline-alkaline water resources offers various benefits including reducing surrounding soil salinity, improving the ecological environment, increasing arable land area, and providing economic advantages to the fishery industry. However, for decades, the characteristics and regulatory mechanisms of microbial communities that affect fishery utilization have not been clear, which restricts their application. In this study, high-throughput 16S rRNA amplicon sequencing was employed to analyze the bacterial community in these water resources. The sequencing yielded high-quality sequences (2,765,063), resulting in the identification of 18,761 bacterial operational taxonomic units (OTUs). Analysis revealed that the type of saline-alkaline water had a more significant influence on the bacterial community compared to seasonal variations within the aquaculture period. The Chao index for saline-alkaline ponds (ASW) was significantly lower (P < 0.05) than for still saline-alkaline water (SSW) and flowing saline-alkaline water (FSW), while the Shannon index for ASW was also significantly lower (P < 0.05) compared to FSW. When comparing ASW to nonaquaculture saline-alkaline water, a decrease in Proteobacteria to 26.87% was noted, particularly α-proteobacteria and γ-proteobacteria, accompanied by a rapid increase in Actinobacteria and Cyanobacteria to 28.60%. Networkx analysis further revealed that ASW significantly increased competition and amensalism from secondary saline-alkaline water microorganisms, resulting in a more solitary bacterial community composition as an adaptive strategy to cope with intense environmental pressures. Key bacterial species such as Pseudomonas, Hydrogenophaga, and Flavobacterium were found to be involved in hydrogen-cycling, nitrogen-cycling, and carbon-cycling, respectively, with all three exhibiting high abundance in FSW. Consequently, FSW demonstrates significant advantages in biogeochemical cycling, pollutant degradation, and the utilization of indigenous probiotic bacteria. Although the surface of abandoned secondary saline-alkaline land was covered with white salt particles, the fishery utilization of saline-alkaline water with low salinity levels (4.0-5.5), and the presence of nitrate and phosphate were identified as primary determinants of bacterial community composition. Nevertheless, a comparison of coastal high-salinity ponds indicated that salinity still selectively affects bacterial communities to some extent. Overall, our study provides valuable insights into the microbial regulation of nitrite during saline-alkaline water aquaculture, thereby aiding in the efficient utilization of secondary saline-alkaline water resources for fisheries.

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.

Acute stress response in gill of Pacific white shrimp Litopenaeus vannamei to high alkalinity

As a multifunctional organ, the gill plays a key role in the regulation of homeostasis. Excessive alkalinity in water can seriously threaten the survival of aquatic animals, however, the studies on the mechanism of alkalinity stress and adaption of crustacea are still limited. In this study, we aimed to investigate the mechanisms of acute alkalinity stress in the gill of Pacific white shrimp Litopenaeus vannamei by integrating physiological, histological, transcriptome, and metabolome analyses, which is an important aquaculture species of crustaceans. The physiological parameters related to homeostasis regulation, oxidative stress, material metabolism, and ammonia detoxification were significantly changed under acute alkalinity stress. There were a considerable number of genes and metabolites that were significantly changed in expression and level, which related to glycolysis/gluconeogenesis, fatty acid metabolism, amino acid metabolism, antioxidation, ammonia metabolism, and glycerophospholipid metabolism, In addition, the local structure of the gill was damaged and accompanied by cell apoptosis. The above results indicate that acute alkalinity stress can lead to damage to the gill structure, and affect its ion transport function, and the genes related to ion transport protein were upregulated. The antioxidant capacity in the gill was strengthened under acute alkalinity stress, at the same time, acute alkalinity stress would induce apoptosis in the gill. The glycogen catabolism in gill was significantly enhanced under acute alkalinity stress, while the lipid anabolism was inhibited, and the mechanism of the ornithine-urea cycle has been further mobilized to alleviate the inhibition of ammonia excretion and the accumulation of metabolic ammonia in the internal environment. In addition, the glycerophospholipid metabolism in the gill was disturbed under acute alkalinity stress. The current study will provide important clues for understanding the alkalinity stress mechanism of crustaceans, and provide an important theoretical basis for the optimization of shrimp aquaculture in saline-alkaline waters.

Integrated characterizations of intestinal bacteria and transcriptomics revealed the acute stress response to carbonate alkalinity in white shrimp Penaeusvannamei

The impact of carbonate alkalinity in saline-alkaline water on aquatic organisms, particularly Penaeus vannamei, a significant species in aquaculture, remains a critical area of study. To elucidate the acute response mechanisms of P. vannamei to elevated carbonate alkalinity environments, we utilized 16S rRNA gene and transcriptome sequencing technologies to analyze intestinal bacteria and gene expressions within various tissues. Our investigation revealed notable changes in specific intestinal bacterial OTUs, whose abundances varied preceding the overall bacterial community, indicating the sensitivity to carbonate alkalinity exposure. These shifts are accompanied by a simplification in bacterial networks and alterations in pathogenic OTUs, notably Aeromonas OTU. Concurrently, gene expression variations were observed across the hepatopancreas, gills, muscles, and intestines, with decreasing numbers of DEGs in the mentioned order. Annotation of these DEGs revealed enrichments in pathways related to transport, catabolism, immune responses, circulatory functions, and lipid metabolism. Notably, correlations between specific intestinal bacterial OTUs and gene expression shifts were identified across these tissues. Several OTUs, attributed to Rhizobiales, Saccharimonadales, Acidovora, and Aeromona, exhibited a correlation with DEGs in all four tissues, primarily associated with amino acid metabolism, signal transduction, and transport and catabolism pathways. Our study provides comprehensive insights into the dynamic responses of P. vannamei to elevated carbonate alkalinity stress. These findings contribute crucial knowledge for effective P. vannamei cultivation in saline-alkaline water, advancing our understanding in this field.

Metabolomic responses based on transcriptome of the hepatopancreas in Exopalaemon carinicauda under carbonate alkalinity stress

High carbonate alkalinity is one of the major stress factors for survival of aquatic animals in saline-alkaline water. Exopalaemon carinicauda is a good model for studying the saline-alkaline adaption mechanism in crustacean because of its great adaptive capacity to alkalinity stress. In this study, non-targeted liquid chromatography-mass spectrometry (LC-MS) metabolomics analyses based on high-throughput RNA sequencing (RNA-Seq) were used to study the metabolomic responses of hepatopancreas in E. carinicauda at 12 h and 36 h after acute carbonate alkalinity stress. The results revealed that most of the significantly differential metabolites were related to the lipid metabolism. In particular, the sphingolipid metabolism was observed at 12 h, the glycerophospholipid metabolism was detected at 36 h, and the linoleic acid metabolic pathway was significantly enriched at both 12 h and 36 h. The combined transcriptome and metabolome analysis showed that energy consumption increased at 12 h, resulting in significant enrichment of AMPK signaling pathways, which contributed to maintain energy homeostasis. Subsequently, the hepatopancreas provided sufficient energy supply through cAMP signaling pathway and glycerophosphate metabolism to maintain normal metabolic function at 36 h. These findings might help to understand the molecular mechanisms of the E. carinicauda under carbonate alkalinity stress, thereby promote the research and development of saline-alkaline resistant shrimp.

Examination of the relationship of carbonate alkalinity stress and ammonia metabolism disorder-mediated apoptosis in the Chinese mitten crab, Eriocheir sinensis: Potential involvement of the ROS/MAPK signaling pathway

The current global status of freshwater resources and deterioration of water quality in general have led to limitations on the scope of freshwater aquaculture. The development of technology that would enable aquaculture under saline-alkaline conditions would be valuable. Therefore, the exploration is needed to understand the damage mechanism of saline-alkaline water, particularly the impact of alkalinity, on fish and shellfish. In this study, Chinese mitten crabs (Eriocheir sinensis) were subjected to different concentrations of carbonate alkalinity (0.00, 4.38, 8.75, 17.50, and 35.00 mmol/L) for 96 h. The survival rates in the 17.50 and 35.00 mmol/L alkalinity groups showed a significant decrease compared to the control group and the groups exposed to lower carbonate alkalinity concentrations (4.38 and 8.75 mmol/L). The exposure to carbonate alkalinity had a significant inhibitory effect on the ammonia excretion rate and led to an increase of ammonia content in hemolymph. However, in contrast to the low carbonate alkalinity exposure groups (4.38 and 8.75 mmol/L), the high carbonate alkalinity exposure group (35.00 mmol/L) exhibited a significant reduction in the concentrations of ammonia and urea nitrogen in hemolymph. Moreover, high carbonate alkalinity exposure was found to induce oxidative stress, as indicated by increased levels of reactive oxygen species (ROS) and malondialdehyde. Additionally, there were notable alterations observed in the activities of antioxidant enzymes such as superoxide dismutase, catalase, and glutathione. Flow cytometry analysis and ultrastructural observations revealed that exposure to carbonate alkalinity can induce apoptosis. In the 8.75, 17.50, and 35.00 mmol/L alkalinity groups, the activation of p38 and JNK pathways was observed, along with an increase in the Bax/Bcl-2 ratio and the expression of caspase 3. In summary, the findings of this study suggested that exposure to carbonate alkalinity can disrupt ammonia metabolism, leading to apoptosis through the activation of the ROS/MAPK signaling pathway. This ultimately results in a decrease in the survival rate of crabs. These results provide valuable insights into the toxicological effects of high carbonate alkalinity exposure and shed light on the tolerance mechanisms of high carbonate alkalinity exposure in crabs.

Effects of chronic saline-alkaline stress on gill, liver and intestinal histology, biochemical, and immune indexes in Amur minnow (Phoxinus lagowskii)

The need to maximize the efficiency with which saline-alkaline waters are used for aquaculture is continually increasing due to unabated increases in the global demand for aquaculture products. Here, the effects of chronic saline-alkaline stress on the growth performance, energy consumption, digestion parameters, antioxidant capacity, ion regulation, and non-specific immunity of Phoxinus lagowskii were studied. Fish were exposed to saline environments (10 parts per thousand) varying in the concentration of sodium bicarbonate [5 (T1), 7 (T2), 9 (T3), and 11 mmol L−1 (T4)]. We observed no significant differences in the weight gain and specific growth rate of fish in environments varying in alkalinity concentrations. Exposure to saline-alkaline stress resulted in a decrease in gills LH (lamellar height) and an increase in LT (lamellar thickness) and intestines VH (villous height) in P. lagowskii. The mean corpuscular hemoglobin concentration; mean corpuscular volume; serum albumin and total protein content; the activity of liver acid phosphatase, alkaline phosphatase, and alanine transaminase; and the messenger RNA (mRNA) expression levels of liver TNF-α, which encodes tumor necrosis factor-α, were significantly higher in the T4 group than in the control and other groups. Exposure to saline-alkaline stress also induced a strong antioxidant response that enhanced cellular defenses. Levels of serum glucose and triglycerides, lipase activity, and the expression of Glut-1 in the intestine significantly increased following exposure to saline-alkaline stress. The activity of Na+/K+-ATPase and Ca2+-Mg2+-ATPase and mRNA expression levels of Na+/H+ exchanger isoform 3 in the gills were significantly higher in the saline-alkaline treatments than in the control group. These findings, coupled with the fact that no mortality was observed, suggest that P. lagowskii could be cultured in saline-alkaline waters, and the optimal alkalinity concentration was <11 mmol L−1. Our study is the first to characterize the effects of exposure to saline-alkaline stress on the histological, biochemical, and immunological parameters of P. lagowskii. Our data indicate that P. lagowskii can adapt rapidly to saline-alkaline environmental stress, suggesting that P. lagowskii could be cultivated at commercial scales in saline-alkaline waters.

Effects of high NaHCO3 alkalinity on growth, tissue structure, digestive enzyme activity, and gut microflora of grass carp juvenile.

With the gradual decrease in freshwater resources, the available space for freshwater aquaculture is diminishing. As a result, saline-alkaline water aquaculture has emerged as a crucial method to fulfill the increasing demand. This study investigates the impact of alkaline water on the growth performance, tissues (gill, liver, and kidney), digestive enzyme activity, and intestinal microbiology in grass carp (Ctenopharyngodon idella). The aquarium conditions were set with sodium bicarbonate (18mmol/L (LAW), 32mmol/L (HAW)) to simulate the alkaline water environment. A freshwater group was the control (FW). The experimental fish were cultured for 60days. The findings revealed that NaHCO3 alkaline stress significantly reduced growth performance, caused alterations in the structural morphology of gill lamellae, liver, and kidney tissues, and led to decreased activity of intestinal trypsin and lipase amylase (P < 0.05). Analysis of 16S rRNA sequences demonstrated that alkalinity influenced the abundance of dominant bacterial phyla and genera. Proteobacteria showed a significant decrease under alkaline conditions, while Firmicutes exhibited a significant increase (P < 0.05). Furthermore, alkalinity conditions significantly reduced the abundance of bacteria involved in protein, amino acid, and carbohydrate metabolism, cell transport, cell decomposition, and environmental information processing. Conversely, the abundance of bacteria associated with lipid metabolism, energy metabolism, organic systems, and disease functional flora increased significantly under alkalinity conditions (P < 0.05). In conclusion, this comprehensive study indicates that alkalinity stress adversely affected the growth performance of juvenile grass carp, likely due to tissue damage, reduced activity of intestinal digestive enzymes, and alterations in intestinal microorganisms.

Comparative study on non-volatile flavor substances of Scylla paramamosain cultured in inland low saline-alkaline water

Comparative study on non-volatile flavor substances of Scylla paramamosain cultured in inland low saline-alkaline water

Effect of high alkalinity on shrimp gills: Histopathological alternations and cell specific responses

High alkalinity stress was considered as a major risk factor for aquatic animals surviving in saline-alkaline water. However, few information exists on the effects of alkalinity stress in crustacean species. As the dominant role of gills in osmotic and ionic regulation, the present study firstly evaluated the effect of alkalinity stress in Exopalaemon carinicauda to determine changes in gill microstructure, and then explore the heterogeneity response of gill cells in alkalinity adaptation by single-cell RNA sequencing (scRNA-seq). Hemolymph osmolality and pH were increased remarkably, and gills showed pillar cells with more symmetrical arrangement and longer lateral flanges and nephrocytes with larger vacuoles in high alkalinity. ScRNA-seq results showed that alkalinity stress reduced the proportion of pillar cells and increased the proportion of nephrocytes significantly. The differentially expressed genes (DEGs) related to ion transport, especially acid-base regulation, such as V(H+)-ATPases and carbonic anhydrases, were down-regulated in pillar cells and up-regulated in nephrocytes. Furthermore, pseudotime analysis showed that some nephrocytes transformed to perform ion transport function in alkalinity adaption. Notedly, the positive signals of carbonic anhydrase were obviously observed in the nephrocytes after alkalinity stress. These results indicated that the alkalinity stress inhibited the ion transport function of pillar cells, but induced the active role of nephrocytes in alkalinity adaptation. Collectively, our results provided the new insight into the cellular and molecular mechanism behind the adverse effects of saline-alkaline water and the saline-alkaline adaption mechanism in crustaceans.

Response of intestinal microbiota to saline-alkaline water in mud crab (Scylla paramamosain) based on multiple low salinity culture modes

IntroductionThe intestinal microbiota acts as an additional “organ” that performs a variety of fu\nctions for the host’s health. However, the composition and role of the intestinal microbiota in Scylla paramamosain cultivated in inland low salinity saline-alkaline water are unknown.MethodsAccordingly, from the perspective of practical production, we explored the intestinal microbiota communities and the critical bacteria of S. paramamosain in normal salinity seawater (NS), coastal low salinity seawater (CS), acute low salinity seawater (AS) and inland low salinity saline-alkaline water (IS).ResultsResults showed that there were significant differences in the diversity composition of intestinal microbiota and the relative abundance of dominant taxa in each group of cultured crabs. Firmicutes, Proteobacteria, Bacteroidota and Campilobacterota were shown to be the major phyla shared by the four groups, with Bacteroidota having the highest relative abundance (27.10%) in the inland low salinity saline-alkaline water group (IS). Fusobacteriota had the highest proportion in IS group compared with other low salinity groups. A total of 284 indicator bacteria were identified, belonging to eight phyla, and their relative abundances were varied significantly (P &amp;lt; 0.05). Genus Carboxylicivirga, as the indicator bacterium of the IS group, may play a critical role in the adaptation of crab to saline-alkaline water environment. Moreover, salinity may exert considerable selective pressure on the entire microbial community.DiscussionThese findings revealed the features of the intestinal microbiome in S. paramamosain in multiple low salinity patterns, and provided candidate probiotics and basic information for crab farming in saline-alkaline water, which was conducive to the development and perfection of mud crab culturing technology in inland low salinity saline-alkaline water.

Transcriptomic Modulation Reveals the Specific Cellular Response in Chinese Sea Bass (Lateolabrax maculatus) Gills under Salinity Change and Alkalinity Stress.

Salinity and alkalinity are among the important factors affecting the distribution, survival, growth and physiology of aquatic animals. Chinese sea bass (Lateolabrax maculatus) is an important aquaculture fish species in China that can widely adapt to diverse salinities from freshwater (FW) to seawater (SW) but moderately adapt to highly alkaline water (AW). In this study, juvenile L. maculatus were exposed to salinity change (SW to FW) and alkalinity stress (FW to AW). Coordinated transcriptomic responses in L. maculatus gills were investigated and based on the weighted gene co-expression network analysis (WGCNA), 8 and 11 stress-responsive modules (SRMs) were identified for salinity change and alkalinity stress, respectively, which revealed a cascade of cellular responses to oxidative and osmotic stress in L. maculatus gills. Specifically, four upregulated SRMs were enriched with induced differentially expressed genes (DEGs) for alkalinity stress, mainly corresponding to the functions of "extracellular matrix" and "anatomical structure", indicating a strong cellular response to alkaline water. Both "antioxidative activity" and "immune response" functions were enriched in the downregulated alkaline SRMs, which comprised inhibited alkaline specific DEGs, revealing the severely disrupted immune and antioxidative functions under alkalinity stress. These alkaline-specific responses were not revealed in the salinity change groups with only moderately inhibited osmoregulation and induced antioxidative response in L. maculatus gills. Therefore, the results revealed the diverse and correlated regulation of the cellular process and stress response in saline-alkaline water, which may have arisen through the functional divergence and adaptive recruitment of the co-expression genes and will provide vital insights for the development of L. maculatus cultivation in alkaline water.