Search Results (649)

Brackish water utilization provides an alternative strategy for alleviating freshwater scarcity in arid agricultural regions; however, the synergistic regulation of salinity, irrigation, and nitrogen management remains unclear. A two-year field experiment was conducted in 2025 and 2026 to investigate the effects of water–nitrogen–salinity interactions on growth, yield formation, resource use efficiency, and fruit quality of pigment pepper (Capsicum annuum L.) under arid conditions in Xinjiang, China. An L9(3³) orthogonal experimental design was adopted with three levels of brackish water salinity, irrigation amount, and nitrogen application rate. The comprehensive production performance of different management strategies was further evaluated using a combined weighting Cloud–TOPSIS approach. The results showed that water–nitrogen–salinity interactions significantly regulated pigment pepper growth, yield formation, and resource utilization, with consistent responses observed across the two experimental years. Increasing irrigation water salinity reduced leaf chlorophyll content (CHL) and nitrogen balance index (NBI), whereas flavonoid content (FLAV) exhibited an increasing trend under moderate salinity stress. Low-salinity irrigation combined with appropriate water and nitrogen inputs maintained higher photosynthetic capacity and nitrogen nutritional status. Yield, water use efficiency (WUE), and partial factor productivity of nitrogen (PFPN) were jointly affected by salinity, irrigation, and nitrogen supply. Excessive salinity significantly reduced crop productivity, while optimized irrigation and nitrogen management alleviated salt stress effects. The T2 treatment (1 g L⁻¹ salinity, 2400 m³ ha⁻¹ irrigation, and 300 kg ha⁻¹ nitrogen application) achieved the highest yield and maintained favorable WUE and PFPN values in both years. Fruit quality responses demonstrated that moderate salinity promoted capsaicinoid accumulation, whereas excessive salinity restricted biomass production and quality improvement. Correlation analysis revealed that photosynthetic nitrogen metabolism indicators were closely associated with yield formation, while flavonoid accumulation showed stronger relationships with quality attributes. The Cloud–TOPSIS evaluation identified T2 as the optimal management strategy under the experimental conditions by balancing yield, quality, and resource use efficiency. These findings indicate that coordinated regulation of irrigation water salinity, water supply, and nitrogen input is essential for achieving efficient brackish water utilization and sustainable pigment pepper production in arid regions. Full article

Macrobrachium nipponense is an economically important freshwater crustacean in China, and growth-related traits are major determinants of its commercial value. Identifying single nucleotide polymorphisms (SNPs) associated with growth-related traits may provide useful molecular markers for the genetic improvement of growth performance. Previous studies have suggested that the cAMP-dependent protein kinase type I regulatory subunit-like gene (Mn-PKA-R1) is involved in the regulation of growth and molting in M. nipponense. In the present study, a cultured full-sib family comprising 120 females and 120 males was used to screen SNPs within the coding region of Mn-PKA-R1, and evaluate their associations with body weight, body length, full length, and abdominal width. Seven SNPs were identified in exon 12, including five nonsynonymous missense variants and two synonymous variants, whereas no SNPs were detected in the other exons examined. The mean effective number of alleles (N_e), observed heterozygosity (H_o), expected heterozygosity (H_e), Nei’s gene diversity (Nei), and polymorphic information content (PIC) were 1.3561, 0.3048, 0.2350, 0.2340, and 0.1962, respectively, in females, compared with 1.3118, 0.2714, 0.1868, 0.1861, and 0.1512, respectively, in males. Four SNPs were significantly associated with growth-related traits in females: C+82748G and A+82750G were associated with body weight and abdominal width, T+82810G was associated with abdominal width, and A+83324G was associated with body weight, full length, and abdominal width (p < 0.05). No significant genotype–trait associations were detected among the SNP loci that could be statistically evaluated in males. Pairwise r² values ranged from 0.001 to 0.693 in females and from 0.000 to 0.351 in males, with generally higher values observed in females within the investigated full-sib family. Females also showed slightly higher mean genetic polymorphism parameters than males, while significant SNP–trait associations were detected only in females within this family. These findings provide candidate SNPs for further validation of their potential utility in marker-assisted selection in M. nipponense. Full article

Small lakes are widespread, yet their biogeochemistry, particularly regarding greenhouse gases, remains insufficiently studied. This article presents the findings from an investigation of six small lakes in the Southern European part of Russia, conducted from September to October 2024. The primary aim was to examine the coupled distribution of methane (CH₄) and sulfide sulfur (a key metabolite of H₂S) in the lake sediments, in relation to geochemical parameters such as pH, Eh, sediment density, moisture, and the contents of sulfate ions (SO₄²⁻), organic matter, and granulometric composition. The studied sediment layers, reaching depths of up to 110 cm, consist primarily of silty clay. The lakes studied represent both freshwater (0.2–0.7 g/L) and brackish (1.3–24.2 g/L) systems. During the study period, the water column exhibited temperatures of 10.4–22.1 °C, pH values of 7.36–8.53, and dissolved O₂ concentrations ranging from 3.16 mg/L (34% saturation) to 11.79 mg/L (125% saturation). Methane concentrations in the water varied widely, from 1.6 µL/L to 37,380 µL/L. The lowest values were found in the highly mineralized Lake Bolshoy Tambukan (1.6–2.0 µL/L), while exceptionally high concentrations were detected in the bottom waters of the thermally stratified freshwater Lake Staroe. In the shallow, productive freshwater lakes, a significant portion of the organic matter undergoes limited mineralization in the water column and settles to the sediments as partially decomposed remains of sand- and coarse-silt-sized organisms. The subsequent degradation of this labile organic matter reduces bottom-water oxygen, triggering intense anaerobic processes in the upper sediment layer. In these freshwater sediments, where sulfate concentrations are relatively low, sulfate reduction is typically suppressed. Combined with an abundance of labile substrates, this condition fosters intensive methanogenesis, resulting in maximum CH₄ concentrations (33–179 µg/g). Under stable thermal stratification, such high CH₄ concentrations can also accumulate in the bottom water (e.g., up to 37. 4 mL/L in Lake Staroe), posing a risk of significant pulse emissions during autumn mixing. Conversely, the brackish Lake Bolshoy Tambukan exemplifies the crucial role of sulfate reduction, which is stimulated by sulfate-dependent anaerobic oxidation of CH₄. This process acts as a powerful natural biogeochemical barrier that curtails the emission of a major greenhouse gas. The sediments of this lake exhibited minimal CH₄ content (0.14–0.57 µg/g) alongside maximal sulfide sulfur concentrations (1.06–8.57 mg/g). Overall, this theoretical and experimental analysis demonstrates that sulfate reduction is a key determinant of redox potential, acid–base conditions, and the vertical distribution of CH₄ in the anaerobic sediments of small lakes in Southern Russia. Given the projected salinization of lakes in steppe and arid landscapes under climate change, a reduction in CH₄ emissions to the atmosphere is likely due to the enhanced sulfate-dependent anaerobic CH₄ oxidation associated with sulfate reduction in the sediments. Full article

Lead (Pb) is a persistent environmental contaminant that poses a significant risk to aquatic primary producers by disrupting photosynthesis, cellular metabolism, and physiological homeostasis. This study investigated the physiological and biochemical responses of two freshwater green microalgae, Mucidosphaerium pulchellum and Micractinium pusillum, exposed to Pb(II) concentrations ranging from 0 to 30 mg L⁻¹. Species-specific responses were evaluated through growth kinetics, chlorophyll fluorescence, lipid accumulation, and fatty acid profiling to elucidate mechanisms underlying Pb stress tolerance. Pb(II) exposure resulted in concentration-dependent inhibition of growth and photosynthetic activity in both species, with marked reductions in quantum yield and increases in photosynthetic inhibition at the highest exposure concentration (30 mg L⁻¹), reaching approximately 95% in M. pulchellum and 93% in M. pusillum. Lipid metabolism exhibited distinct species-specific responses: M. pulchellum showed a progressive decline in total lipid content, whereas M. pusillum exhibited enhanced lipid accumulation under moderate Pb exposure followed by depletion under severe stress. Fatty acid analysis revealed significant membrane lipid remodeling, characterized primarily by reductions in polyunsaturated fatty acids, particularly α-linolenic acid (C18:3), with stronger alterations observed in M. pulchellum. These findings demonstrate that Pb toxicity involves interconnected effects on photosynthetic efficiency, carbon allocation, and membrane lipid composition, with species-specific differences in physiological resilience. The combined application of chlorophyll fluorescence and lipid-related biomarkers provides a sensitive approach for assessing heavy-metal stress responses and improving understanding of Pb tolerance mechanisms in freshwater microalgae. These findings provide a physiological basis for the development of sustainable biomonitoring approaches for freshwater ecosystems. Full article

Aquaponics integrates fish culture with hydroponic plant production, enabling a sustainable approach to food production through nutrient recycling. This study evaluated the growth performance of three freshwater fish species—catfish (Silurus asotus; T₁), leather carp (Cyprinus carpio nudus; T₂), and goldfish (Carassius auratus; T₃)—reared in an indoor aquaponics system with three replications over 50 days and assessed their effects on water quality and apple mint (Mentha suaveolens) production. Water quality, fish, and plant growth parameters were monitored throughout the study. T₁ exhibited significantly greater fish and plant growth performance than T₂ and T₃ (p < 0.05), thereby increasing nutrient input into the culture water. In contrast, T₂ and T₃ exhibited lower fish growth but higher survival rates. Significant differences in fish proximate composition were observed among treatments (p < 0.05). T₃ exhibited higher moisture and crude lipid contents, whereas T₁ and T₂ showed higher crude protein contents. Water quality and mineral concentrations remained within acceptable aquaponic ranges. Species-specific differences influenced nutrient accumulation and system dynamics, demonstrating that fish species selection strongly influences both fish productivity and plant performance. The catfish–apple mint combination showed the highest potential for nutrient recycling and biomass production under controlled conditions, but long-term sustainability may depend on optimizing catfish management to mitigate mortality. Full article

New health-promoting food ingredients should combine nutritional functionality, traceable production and sustainable sourcing. Freshwater and brackish gammarid amphipods are usually considered ecological indicators, fish prey or invasive crustaceans, but their biochemical and ecological traits suggest a candidate role as low-trophic aquatic biomass. This narrative review evaluates gammarids primarily as EPA-oriented crustacean biomass and as a potential source of protein, minerals, chitinous material and processing fractions for feed, supplement and functional-food research. Available data indicate meaningful long-chain omega-3 content, especially EPA, but direct evidence for human health effects, bioavailability, clinical efficacy and industrial cultivation remains limited. Wild harvest is unlikely to provide a safe or standardized raw material. The central proposition is, therefore, that gammarid-derived ingredients should be developed through controlled benthic production systems, followed by hygienization, fractionation and safety validation. The most realistic near-term pathway is not direct consumption of whole animals, but standardized feed ingredients, EPA-oriented lipid blends, protein–lipid fractions and supplement-grade materials after regulatory assessment. The review distinguishes established evidence from technological hypotheses and identifies the research required before gammarids can be considered reliable industrial ingredients. Full article

High-altitude environments expose aquatic organisms to complex environmental challenges, including fluctuations in dissolved oxygen levels, water temperature, and other habitat conditions. The freshwater snail Cipangopaludina cathayensis has limited dispersal ability and is strongly associated with local habitat conditions, making it a suitable species for investigating biological responses to long-term environmental variation. In this study, high-altitude and low-altitude populations of Cipangopaludina cathayensis were compared using biochemical assays, shell elemental composition analysis, transcriptomics, and metabolomics to explore altitude-associated physiological and molecular responses. Environmental monitoring showed that the high-altitude habitat exhibited lower water temperatures, greater thermal variability, and significantly higher dissolved oxygen availability than the low-altitude habitat, indicating distinct environmental conditions between the two populations. The high-altitude population exhibited significantly higher superoxide dismutase (SOD) and pyruvate kinase (PK) activities than the low-altitude population, whereas malondialdehyde (MDA) content and total ATPase (T-ATPase) activity showed no significant differences between populations. Shell microstructure and elemental analyses revealed altitude-associated differences in biomineralization. Transcriptomic analysis identified differentially expressed genes involved in intracellular transport, including KIF10, KIF11, KIF13, KIF17, MYO3, and MYO7A, as well as apoptosis-associated genes, including CASP2, CASP3, and BCL-2. Integrated transcriptomic and metabolomic analyses further highlighted purine metabolism, D-amino acid metabolism, insulin resistance, and alanine, aspartate and glutamate metabolism as shared enriched pathways between the two populations. These findings indicate that Cipangopaludina cathayensis may cope with high-altitude environments through coordinated regulation of antioxidant defense, intracellular transport, apoptosis-associated pathways, and metabolic homeostasis. Full article

Interactions between cyanobacteria and eukaryotic algae are traditionally viewed as favoring cyanobacteria, which are often the dominant competitors in freshwater ecosystems. However, increasing evidence suggests that eukaryotic algae also possess effective chemical defenses capable of suppressing cyanobacterial proliferation. In this study, the anti-cyanobacterial potential of a methanolic biomass extract of the green microalga Chlorella vulgaris against the bloom-forming cyanobacterium Microcystis aeruginosa was investigated. Optical density measurements revealed the inhibition of cyanobacterial growth, with extract concentrations of 0.4–1.6 mg mL⁻¹ significantly reducing biomass accumulation. The lowest concentration (0.2 mg mL⁻¹) stimulated the accumulation of phycobiliproteins, whereas concentrations of 0.8–1.6 mg mL⁻¹ significantly decreased phycobiliprotein content, indicating progressive physiological impairment. The results suggest that the highest extract concentration applied may also cause alteration in phosphate acquisition. Lipid profiling of the Chlorella biomass showed that 97% of the extractable lipids consisted of methanol-soluble fatty acids, with C18 fatty acids predominating among the 20 identified compounds. These metabolites are reported to possess allelopathic activity and therefore represent plausible contributors to the observed inhibition. These findings support that anti-cyanobacterial activity may represent a widespread ecological trait of Chlorella and potentially other green microalgae, providing a promising foundation for environmentally friendly cyanobacterial bloom management. Full article

As a microalga of significant economic value, the polysaccharide synthesis efficiency and bioactivity of Spirulina platensis are significantly influenced by the culture condition. In this study, S. platensis H11 obtained by space mutagenesis, was systematically compared to the growth characteristics, polysaccharide properties, and antioxidant activities between seawater and freshwater culture conditions. The results showed that the biomass concentration (8.87 g L⁻¹) and polysaccharide yield (5.46 g L⁻¹) of the strain in the seawater condition were increased by 16.1% and 14.7%, respectively, compared with that in the freshwater condition. Seawater-derived polysaccharides (SSPS) featured an α-configuration glucan backbone and exhibited higher molecular weight (466.19 kDa) and an additional β-configured anomeric signal compared with FSPS. Despite having lower contents of sulfate groups (0.56% DW) and glucuronides (4.92% DW) by 39.3% and 33.5%, respectively, compared to FSPS (0.78% sulfate group, 6.57% glucuronide), SSPS exhibited significantly enhanced hydroxyl radical-scavenging activity, demonstrated by a decreased IC₅₀ value of 2.53 mg mL⁻¹ as opposed to 3.07 mg mL⁻¹. The present study confirms that seawater cultivation is an effective strategy for inducing the synthesis of highly active polysaccharides in space mutant strains, and provides a theoretical basis for the targeted production of polysaccharides in S. platensis and their functional and precise application. Full article

Iron oxides are crucial to soil organic carbon (SOC) sequestration in wetland ecosystems. Whether vegetation drives soil microorganisms to regulate iron–carbon interactions and influence SOC sequestration capacity remains controversial. Thus, this study investigated iron–carbon coupling processes and their microbial drivers in the Caohai alpine freshwater closed wetland, Guizhou Province, China. Using metagenomic sequencing and physicochemical analyses, we compared vegetated areas (Phragmites australis and Scirpus tabernaemontani) with bare flats (BF). Levels of SOC, microbial necromass carbon (MNC), and plant-derived carbon (PC) in vegetated soils were significantly higher than those in BF (p < 0.05). In all study regions, the PC/SOC ratio (PA: 27.89 ± 3.59 %; ST: 24.58 ±1.86 %; BF: 24 ±2.82 %) exceeded the MNC/SOC ratio (PA: 15.58 ± 0.94 %; ST: 15.95 ± 0.73 %; BF: 13.06 ±1.30 %). The PC/SOC and MNC/SOC ratios were higher in vegetated areas than in BF areas. Compared with BF, vegetation enhanced wetland SOC stability and promoted carbon sequestration. Iron-bound organic carbon $\left({\mathrm{Fe}}_{\mathrm{d}}–\mathrm{OC}\right)$ content was substantially greater in vegetated soils (PA:0.34 ± 0.08 g/kg; ST:1.07 ± 0.58 g/kg) than in BF (0.14 ± 0.08 g/kg) (p < 0.05). Based on the ${\mathrm{Fe}}_{\mathrm{d}}–\mathrm{OC}$/${\mathrm{Fe}}_{\mathrm{d}}$ ratio (PA: 22.87 ± 14.00 %; ST: 23.00 ± 13.90%; BF: 5.36 ± 3.40 %), ${\mathrm{Fe}}_{\mathrm{d}}–\mathrm{OC}$ associations in vegetated soils were dominated by stable coprecipitation, whereas unstable adsorption prevailed in BF. In all study regions, the abundances of iron-reducing bacteria (FeRB) and iron-oxidizing bacteria (FeOB) peaked in BF. Several FeRB genera, including Thiobacillus, Intrasporangium, Gallionella, and Nocardioides, were significantly and positively correlated with ${\mathrm{Fe}}_{\mathrm{d}}$ (p < 0.05). Conversely, Geobacter and Nitrospira exhibited significant negative correlations with ${\mathrm{Fe}}_{\mathrm{d}}–\mathrm{OC}$ and PC (p < 0.05). The FeOB genera—Thioalkalivibrio, Thiohalobacter, and Pseudomonas—were negatively correlated with ${\mathrm{Fe}}_{\mathrm{d}}$. Vegetation presence appears to influence microbial metabolic potentials through the provision of rhizodeposits and the modulation of rhizosphere conditions, thereby affecting ${\mathrm{Fe}}_{\mathrm{d}}–\mathrm{OC}$ associations and contributing to SOC sequestration in wetland soils to some extent. These findings provide critical insights into plant–microbe–mineral interactions and a scientific framework for predicting carbon sink dynamics in wetland ecosystems. Full article

This study aimed to investigate the effects of salinity changes on serum biochemistry, hormonal profiles, splenic immune function, hepatic lipid metabolism and intestinal microbiota of the F₂ generation of Chinese sturgeon (Acipenser sinensis) under freshwater and seawater acclimation (15–23.2 psu) conditions. A 30-day indoor culture experiment showed that seawater acclimation only induced a declining trend in juvenile growth without statistical significance compared to the freshwater group (p > 0.05). The levels of triglycerides (TG), total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), alkaline phosphatase (ALP) and albumin II (ALBII) in the freshwater group were markedly lower than those in the seawater group (p < 0.05), while alanine aminotransferase (ALT), aspartate aminotransferase (AST), high-density lipoprotein cholesterol (HDL-C) and total protein (TPII) showed no significant differences (p > 0.05). The serum triiodothyronine (T3) concentration was significantly higher, and chloride ion (Cl⁻) was lower in freshwater individuals (p < 0.05). Cortisol, testosterone, K⁺, Na⁺, Ca²⁺, thyroid-stimulating hormone and T4 remained unchanged between the two salinity environments (p > 0.05). In gill tissues, lipase (LPS) and fatty acid synthase (FAS) activities were lower, whereas lipoprotein lipase (LPL) activity was higher in the freshwater group (p < 0.05), and no obvious difference was observed in hepatic metabolic enzymes. The splenic complement C4 content was significantly decreased in freshwater sturgeon (p < 0.05), while splenic C3, IgM and serum immune indices showed no statistical differences. All alpha-diversity indices of intestinal microbiota were significantly higher in the seawater group (p < 0.05). At the phylum level, the intestinal flora in the seawater group was dominated by Proteobacteria (69.6%) and Fusobacteriota (14.9%), whereas Fusobacteriota accounted for 81.5% in the freshwater group. At the genus level, seawater samples exhibited richer microbial composition including Sphingomonas, Cupriavidus and Cetobacterium, while the freshwater microbiota was overwhelmingly dominated by Cetobacterium (81.5%). In conclusion, salinity significantly regulates serum biochemistry, hormone secretion, lipid metabolism, splenic immunity and intestinal microbiota of the F₂ generation of Chinese sturgeon. The freshwater environment benefits lipid metabolism, thyroid hormone levels, and growth performance, with a simplified intestinal microbial structure. Seawater acclimation maintains higher gut microbial diversity and immune homeostasis, but induces osmotic stress, restricts thyroid hormone secretion and redistributes energy supply, thereby inhibiting fish growth. This study provides a theoretical basis for salinity domestication and scientific culture management of Chinese sturgeon. Full article

Freshwater scarcity and soil salinization limit coastal agriculture, and brackish water irrigation may help alleviate regional water shortages. This study examined the effects of irrigation water salinity on water–salt dynamics and ion distribution in coastal saline soil from Laizhou Bay. Repacked soil column experiments were conducted using a freshwater control and brackish water treatments with TDS levels of 1, 3, and 5 g L⁻¹. Soil water content and electrical conductivity were monitored at 1 min intervals at five depths, and pore water ion composition was analyzed after infiltration. Higher salinity was associated with reduced cumulative infiltration and infiltration rates, delayed wetting front migration, and longer infiltration durations. Freshwater cumulative infiltration reached 11.94 L, whereas the 3 and 5 g L⁻¹ treatments decreased final cumulative infiltration by more than 11%. Soil EC increased with salinity, with higher values occurring mainly in the middle and lower soil layers. Na⁺ and Cl⁻ were the dominant ions contributing to salinity risk and moved downward with the wetting front. Low-salinity brackish water caused less short-term infiltration inhibition and salt accumulation risk than higher-salinity water under laboratory column conditions. However, field validation, crop response evaluation, economic feasibility assessment, and long-term salt balance analysis are required before practical irrigation recommendations can be made. Full article

The severe slagging caused by high-alkali coals restricts the utilization of Xinjiang coal resources in China. This study investigates the mineral composition, geochemical characteristics, modes of occurrence, and controlling factors of alkali and alkaline earth metals in high-alkali coals from the Dananhu Coalfield, Turpan–Hami Basin. The investigated coals are classified as lignite, characterized by low ash yield, extra low sulfur, and medium–high alkali contents. Quartz and kaolinite are dominant, with accessory calcite, K-feldspar, pyrite, gypsum, siderite, celestite, and Ba-bearing celestite. Compared to average Chinese coals, Na, Mg, Ca, and Cl are enriched, with the shallowest No. 3 coal seam showing the highest enrichment. Based on the correlation analysis, K is likely associated with K-bearing aluminosilicates (e.g., K-feldspar and illite), while Ca, Mg, and Na probably exhibit both organic and inorganic affinities. Sequential extraction results indicate that Na is predominantly water-soluble and ion-exchangeable, whereas Ca and Mg are largely ion-exchangeable and HCl-soluble. The abundant cell cavities and oxygen-containing functional groups in lignite provide both binding sites and accommodation space for Ca, Mg, and Na. Despite a continental freshwater depositional setting, tectonic isolation and persistent arid conditions potentially promoted epigenetic enrichment of Na, Mg, and Ca. Closed hydrogeological units formed by tectonic movements restricted leaching and enhanced evaporation, concentrating these elements in the coal seams. Future research should focus on implementing economically feasible dealkalization pretreatment processes for the clean utilization of high-alkali coals. Full article

Dissolved organic matter (DOM) plays a key role in shaping lake microbiomes and water quality, yet its spatial variability and regional links to microbial activity remain unclear. Using three-dimensional excitation–emission matrix and self-organizing map analysis on 38 samples from a human-impacted lake network in Hubei (affected by tourism, agriculture, and urban areas), this study clarifies DOM heterogeneity and its environmental connections. Microbial metabolic activity represented by total bacterial content (BC) and Escherichia coli (E. coli) activity was rapidly and automatically measured with a ColiMinder device. Random forest (RF) modeling and principal component analysis (PCA) were applied to identify key drivers of microbial activity and to clarify correlations between DOM characteristics and microbial activitiy. Results indicated that although DOM in all three sectors primarily originated from microbial activities during the flat-water period, Tuanhu (TH) exhibited a higher degree of DOM humification and a larger average relative molecular mass, reflecting stronger terrestrial source characteristics. RF analysis identified NH₄⁺ as the main predictor of both BC and E. coli levels, while total organic carbon (TOC) and total nitrogen (TN) were also important predictors. PCA further revealed clear differences in DOM composition across the lakes. DOM in TH was predominantly autochthonous, whereas DOM in Miaohu (MH) and Guozheng (GZ) was mainly of humic origin. This study adopts an integrated method combining rapid microbial detection, EEM and DOM–microbe correlation analysis to analyze human disturbances across segmented connected lakes in Hubei. It provides scientific support for targeted water quality management of human-influenced freshwater. Full article

Frozen storage is widely used to preserve shrimp products, but the multiscale mechanisms underlying quality deterioration in giant freshwater prawn remain insufficiently understood. This study investigated changes in water retention, oxidative stability, muscle structure, and protein conformation in Macrobrachium rosenbergii stored at −20 ± 2 °C for 0, 1, 3, and 5 months. Thawing and cooking losses, water-holding capacity, freshness and oxidation indices, texture, histology, low-field nuclear magnetic resonance, Fourier transform infrared spectroscopy, and intrinsic fluorescence were comprehensively evaluated. After 5 months, thawing loss increased from 8.21% to 12.51%, cooking loss increased by 55.0%, and water-holding capacity decreased from 85.45% to 68.46%. The total volatile basic nitrogen, protein carbonyl content, thiobarbituric acid reactive substances (TBARS; 0.186 to 0.528 mg MDA/kg), and myofibril fragmentation index increased progressively, while free sulfhydryl and salt-soluble protein contents declined. Shear force, hardness, cohesiveness, gumminess, and chewiness also decreased, accompanied by muscle fiber separation and an increase in white void area from 0.04% to 3.46%. Low-field nuclear magnetic resonance revealed decreases in the short-relaxation P₂b and P₂1 populations and an increase in the dominant P₂2 population, indicating relative water-population redistribution. Meanwhile, α-helix content decreased from 18.83% to 16.28%, β-sheet content increased from 25.05% to 28.22%, and maximum fluorescence intensity decreased by 31.9%. These coordinated changes suggest that prolonged frozen storage weakened the myofibrillar network through water redistribution, lipid and protein oxidation, protein fragmentation, conformational rearrangements, and tissue disruption. The findings provide a multiscale basis for developing water-retention and quality-control strategies for frozen giant freshwater prawn. Full article