Search Results (1,199)

River morphological changes significantly influence water purification functions; however, systematic research on the evolution of natural river morphology and its underlying mechanisms remains insufficient. This study investigates the Shiwuli River, a typical tributary of Chaohu Lake, by quantitatively analyzing its morphological evolution characteristics based on high-resolution satellite imagery from 2014 to 2024. Combined with field monitoring data from all four seasons of 2024, the study explores the influence mechanisms of river sinuosity, cascade flow, and wetlands on water purification. The results indicate significant morphological changes in the Shiwuli River: the total length decreased by 3.95 km, sinuosity decreased by 0.22, and the average width increased by 27.85 m. The comprehensive attenuation coefficient of pollutants in the monitored sections was consistently greater than zero, demonstrating the self-purification capacity of the natural meandering river, with the highest purification capacity observed in summer and the weakest in winter. Dissolved oxygen (DO) content was generally higher in concave banks than in convex banks, and the rate of increase in DO per unit length rose with increasing sinuosity. The cascade flow formed by rolling dams significantly enhanced DO concentration (by 19.23–26.25%), with average pollutant reduction rates ranging from 12.64% to 33.76%. The wetland sections exhibited average reduction rates of 79.07% for total phosphorus (TP), 39.33% for total nitrogen (TN), 47.43% for ammonia nitrogen (NH₃-N), and 45.67% for chemical oxygen demand (COD), demonstrating significantly better purification effects compared to the main river channel. This study reveals that the synergistic interaction among river sinuosity, cascade flow, and wetland systems enhances the water body’s self-purification capacity, providing a scientific basis for river ecological restoration and sustainable utilization of water resources. Full article

The significant CO₂ emissions from cement manufacturing and overuse of natural aggregates, especially river sand mining, have been a global environmental concern for decades. This is a review study that aimed to evaluate the solution by reviewing past studies on the incorporation of supplementary cementitious materials (SCMs) and recycled aggregates (RAs) to produce sustainable concrete (SC). Regarding environmental consequences, the results highlighted that the cement industry accounts for a 5–8% carbon footprint. Concurrently, the demand for high-quality river sand has escalated, leading to widespread river degradation, altered channel morphology, and effects on river ecosystems. Past studies’ experimental results indicate that silica fume (SF), as an effective SCM, enhances the strength and durability of sustainable concrete to its optimal levels. However, the higher RA content resulted in reductions in engineering properties. The published studies also reported that lower percentages of SF combined with RAs had a positive effect on the strength and durability of design mix concrete, thereby further strengthening the findings of this review. This factor was found to be missing in most studies. A cost–benefit analysis for combined SCMs and RAs was introduced in this study. This review study evaluated the cost–benefit analysis of 1 m³ of sustainable concrete. The highest benefit was observed at 20.97% in a study when optimized 10%SF + 100 RAs were combined. It showed that the combined use of SCMs with RAs at optimal levels satisfied the strength and durability requirements. In addition, the benefits of sustainable concrete were achieved without any cost increase, a new outcome revealed by this review. Full article

Fish are an important criterion for evaluating the quality of river ecosystems, and water flow characteristics may be the main factor affecting the living environment of fish. As the main component of a river, the topography of the bank slope has a significant impact on the characteristics of nearshore water flow. At the same time, eco-revetment structure has the functions of smoothing water flow, maintaining stable bank slopes, and improving river ecology. It can reset the distribution of nearshore water flow and provide a stable living environment for fish. This study focuses on the middle and lower reaches of the Yangtze River as the research area, with the main research object being grass carp. We construct a generalized model based on river morphology and flow characteristics. A new eco-revetment structure is proposed with the main research area of nearshore waters, aiming to improve the flow state of nearshore water and enhance its ecology. A suitability evaluation model for grass carp habitat was constructed based on Large Eddy Simulation and fuzzy mathematics theory, with water flow as the main habitat influencing factor. We study the distribution pattern of suitability for grass carp habitats near nearshore waters. The results indicate that the nitrogen phosphorus ratio near the top of the revetment structure is close to the Redfield value and can be used as a stable foraging area for fish. The flow rate is the dominant factor for the habitat of juvenile grass carp. When there is no vegetation, the suitability of region A is 0–0.4, the suitability of region B is 0.2–0.6, and the area proportion of the high suitability area (0.4–0.6) is maintained at 10–30% with the increase in the flow rate. Region C is not suitable for the long-term survival of juvenile grass carp. When there is vegetation, the suitability of region A ranges from 0 to 0.6, and the proportion of low-suitability areas decreases. The suitability of region B ranges from 0.4 to 0.6, and the proportion of suitable areas is positively correlated with flow velocity. The suitability of region C is consistent with the absence of vegetation. The dominant factors for fish spawning habitat are flow velocity, vorticity, and kinetic energy gradient. The spawning suitability zone (HSI ≥ 0.6) is located between the spanwise structures, with a proportion positively correlated with flow velocity and higher suitability on the deep-water side. The existence of fish has little impact on the habitat. In the juvenile fish habitat area, the proportion of areas suitable for juvenile fish in region A has slightly decreased, and the suitability of region B has increased. In spawning grounds, an HSI ≥ 0.6 accounts for about 5% of the decrease compared to no-fish conditions, and overall can meet the needs of fish habitat, foraging, and spawning. This article provides ideas and foundations for the design of future new eco-revetment structures and a suitability analysis of living environments for fish. Full article

Introduction: Brown trout (Salmo trutta L.) is a salmonid fish considered a genetically and geographically highly structured species. The species is catalogued as vulnerable in the Spanish Red List since 1992. Based on morphological differentiation, some authors have proposed splitting Salmo trutta into many taxa and in recent years, several binomials involving morphologically differentiated Western Mediterranean brown trout morphs have regained relevance as distinct species and are now assessed in the IUCN Red List. However, Spanish legislation still considers a single species, S. trutta, inhabiting Atlantic and Mediterranean rivers. Analyses of mitochondrial DNA variation across the species’ native range have revealed numerous matrilineal lineages and helped disentangle the phylogenetic relationships and biogeographic history of brown trout. Four largely distant evolutionary lineages defined by sequencing the mitochondrial control region (Adriatic, AD, Mediterranean, ME, Atlantic, AT and Duero, DU) are native among the Iberian brown trout populations. Stocking activities have resulted in introgressive hybridization of these native populations with non-native northern Atlantic stocks throughout the Iberian rivers and compromise the evolutionary singularities of brown trout in the Iberian Peninsula. Methodology: In this study, we compare complete mitogenomes from Iberian brown trout specimens with those from other regions, using both newly sequenced samples and whole mitogenomes from the GenBank database and estimate their divergence times relative to those observed among species of other Salmoninae genera, such as Oncorhynchus and Salvelinus, to assess patterns of species-specific divergence among Iberian brown trout populations. Results: The evolutionary relationships of the specimens using their mitogenomes fitted with previous analyses using partial mitochondrial sequences and confirmed the strong differentiation among the Iberian lineages. All the branches involving distant Iberian mitogenomes are sister branches with taxa historically described under different binomials (such as Salmo macrostigma, S. multipunctatus, S. pallaryi). Conclusions: The results provide evidence supporting the existence of potentially distinct and undescribed native Salmo species in the Iberian rivers. Full article

In the Iberian Peninsula, the rapid expansion of the invasive species Alburnus alburnus (bleak) has intensified its contact with several endemic cyprinid species, raising concerns about hybridization, introgression, and the loss of genetic diversity. Despite increasing evidence of hybridization, data remain limited for many Iberian River basins, where endemic species persist in fragmented and vulnerable habitats. The aim of this study is to assess the extent and spatial distribution of hybridization between the bleak and the following native cyprinid species, Anaecypris hispanica (jarabugo), Iberochondrostoma lemmingii (pardilla), Pseudochondrostoma willkommii (Guadiana nase), and Squalius alburnoides (calandino), across several rivers within the Guadalquivir Basin. To this end, Sanger sequencing will be performed on the mitochondrial cytochrome b gene (maternal lineage; approximately 1000 base pairs (bp)) and the nuclear β-actin gene (paternal lineage; approximately 950 bp) from individuals of all endemic species and the bleak. Parental species and putative hybrids were initially identified in the field using diagnostic morphological and meristic characters, including number of rays in the anal fin morphology, mouth position, and the number of lateral line scales. Molecular analyses will include haplotype network reconstruction and phylogenetic tree inference to evaluate relationships among individuals from different species and to assess lineage divergence. The results will allow us to: (1) detect hybrids between the bleak and endemic cyprinids, (2) identify hybridization events among endemic cyprinid species, and (3) evaluate the correspondence between diagnostic morphological and meristic traits and the molecular identification of hybrid individuals. Overall, these findings will provide key information for the conservation management of endangered Iberian freshwater fishes in the context of invasive species expansion and global change. Full article

The floodplains of the Paraná and Paraguay rivers form the Chaco wetland, one of the most species-rich plant ecosystems in Argentina. Because wild grasses can serve as reservoirs of fungal species that cause disease and mycotoxin contamination of cereal crops, we examined asymptomatic, wild grasses from the Chaco wetlands for the presence of the genus Fusarium, which includes multiple species that cause agriculturally important diseases and/or mycotoxin contamination of crops. We focused our efforts on the identification and characterization of the multispecies lineage known as the Fusarium fujikuroi species complex (FFSC). Using morphological traits and partial DNA sequences of the TEF1 gene, we determined that 58 isolates recovered from the grasses were members of FFSC. Fifty of the isolates were identified as one of six FFSC species, including the economically important plant pathogenic species F. proliferatum, F. subglutinans, and F. verticillioides. To our knowledge, two of the species, F. anthophilum and F. pseudocircinatum, have not been reported previously in Argentina. Our analyses also indicated that eight of the FFSC isolates were a novel species, herein described as Fusarium varsavskyanum. A polymerase chain reaction (PCR) assay and genome sequence data indicate that each isolate of F. varsavskyanum isolate had only one mating type idiomorph (MAT1-1 or MAT1-2), which suggests that the fungus is heterothallic. Genome sequence analysis indicated that F. varsavskyanum has the genetic potential to produce, (i) the emerging mycotoxins fusaric acid and beauvericin (or enniatins); (ii) the pigments bikaverin, carotenoids, and fusarubin; and (iii) the plant hormones auxins, cytokinins, and gibberellins. Thus, asymptomatic grasses from the Chaco wetland can harbor Fusarium species that in some agroecosystems can cause economically important diseases and/or mycotoxin contamination of crops. It remains to be determined whether the genotypes of Fusarium species that occur on the wetland grasses, including F. varsavskyanum genotypes, can negatively impact agriculture. Full article

Habitat alteration and biological invasions are two main drivers of biodiversity loss at the global scale. Eutrophication and invasive fish greatly disturb freshwater native communities. This is of particular conservation concern in the Iberian Peninsula (Portugal and Spain), where fish fauna display a high level of endemism. For this eco-region, there is a dearth of information on the interactions among water quality, physical condition and parasites of invasive fishes. Consequently, the aim of this study was to assess the effect of nutrient enrichment on health status and parasitological traits in the invasive mosquitofish Gambusia holbrooki inhabiting an Iberian river. Water (n = 18 replicates, three per site) and fish (n = 400 individuals, 33–34 ind. per site and year) samples were collected in September 2024 and 2025 along the River Bullaque (central Spain). Sampling effort was standardised among sites, with the following parameters consistent: seine and pond nets were used, deployed by wading; 10:00 solar time; 1.5 h duration; personnel (the same seven trained researchers); and weather/environmental conditions; ensuring methodological consistency and data comparability. Laboratory procedures were carried out near the sampling sites to minimise both fish stress and distortions to parasite communities. Morphological and parasitological parameters were compared between mesotrophic and eutrophic reaches (six sampling sites, three per reach). Body condition and health assessment index* were greater under eutrophic conditions. Fluctuating asymmetry (a measure of developmental instability) was significantly higher for eye diameter in the mesotrophic reach. Parasite taxonomic composition differed between reaches, with more digeneans and cestodes in the mesotrophic sites, whereas ciliates and monogeneans were more abundant in mosquitofish from the eutrophic reach. Parasite prevalence, abundance and index of life-cycle complexity (heteroxenous species) were lower in the eutrophic reach. These results strongly suggest that eutrophication can facilitate mosquitofish invasiveness. This is reflected in a variety of morphological and parasitological traits, such as better body condition, health status, developmental stability, parasite resistance and tolerance. Overall, these parameters indicate that mosquitofish is taking advantage of anthropogenic impacts to improve their level of establishment and subsequent spread throughout Iberian fresh waters. Full article

The Tonglushan ore field is an important component of the polymetallic mineralization belt in the middle and lower reaches of the Yangtze River in China. The skarn-type Cu, Fe, Au, and Mo molybdenum deposits are mainly developed in the contact zone between the rock mass and the strata, as well as in the contact zone between residual and capturing bodies in the rock body. The distribution of ore bodies is controlled by faults and strata, but there is a lack of large-scale geophysical information on the contact relationship between the ore-forming geological body and the host rock and on the deep spatial morphology of the ore-forming structure and intrusion rock. The study uses the JS-WEM2 wide-field electromagnetic instrument and the RS230 spectrometer to conduct the ground frequency domain electromagnetic and radiometric spectrometry measurements on four profiles. The measurement results indicate that the fault distribution in the Tonglushan ore field is predominantly in the NW-trending and NE-trending directions. The NW-trending Tonglushan–Lijiashan fault (F2) is a steeply dipping fault; the NE-trending faults are minor, with steep dips, generally extending no deeper than −1000 m. The Tonglushan stock exhibits the northeastward uplift, characterized by southward overlap and southeastward dip. The deep resistivity is greater than 3000 Ω·m, while the resistivity below −1000 m is less than 2000 Ω·m due to the fault influence. The ore bodies are mainly distributed along the contact zones where variations in the occurrence of the rock intersect with the strata. On resistivity profiles, these zones show the gradient variation in resistivity and the distorted shape of the resistivity contour line. The radioactive element contents of wall rock above the ore bodies are characterized by high U, high Th, and low K. The Wide-Field Electromagnetic Method (WFEM) can effectively detect the distribution and morphology of rocks and faults, and combined with the radioactive characteristics of geological bodies, it can effectively identify concealed faults and the favorable mineralization target areas. Novelty: The study combines the WFEM with radiometric measurements to reduce uncertainty in exploration compared to using only one method. It improves the detection accuracy and target identification ability of deep hidden ore bodies, providing the new technical method for deep mineral exploration in complex structural areas. Full article

Cultivable fungi are important components of freshwater ecosystems, yet their diversity in Amazonian aquatic environments remains poorly explored. This study evaluated cultivable fungal communities associated with water, sediment, and submerged wood in the Negro, Solimões, and Tapajós Rivers, representing the major black-, white-, and clear-water systems of the Amazon basin, respectively. Samples were collected along 25 m transects, fungi were isolated on potato dextrose agar, grouped into morphotypes, and identified morphologically. Diversity was assessed using richness, Shannon, Simpson, Pielou, and Sørensen indices. Overall, 130 isolates and 75 morphotypes were recorded, with a predominance of morphotypes assigned to filamentous Ascomycota and widespread occurrence of Aspergillus and Penicillium. Solid substrates yielded greater fungal abundance and richness than water samples. Submerged wood from the Negro River showed the highest overall cultivable fungal abundance, whereas the Tapajós River showed the highest diversity in water and sediment and the highest richness in both substrates. The Solimões River showed stronger dominance by a limited number of morphotypes, particularly in submerged wood. Sørensen similarity values indicated low compositional overlap among rivers, especially for submerged wood communities, suggesting apparent differentiation among river-associated cultivable fungal assemblages. Together, these exploratory results suggest that substrate type, hydrochemical differences, and potential temporal effects may be associated with the structure of cultivable fungal communities in Amazonian rivers. Full article

Accurate landslide identification is crucial for enhancing emergency response capabilities during destructive geological hazards. Although deep-learning-based semantic segmentation has demonstrated effectiveness, substantial variations in landslide scales and environmental similarities continue to challenge existing methods. This paper systematically constructs a new co-seismic landslide dataset for the Yarlung Zangbo River basin based on the 2017 Nyingchi earthquake, effectively filling a critical regional data gap. This paper proposes CETransUNet (coordinate attention and edge-guided attention transformer UNet), a novel landslide detection model that integrates ResNet and Transformer architectures. Specifically, a coordinate attention (CA) module is introduced within the skip connections between the encoder and decoder. This module encodes positional information along both horizontal and vertical spatial directions and dynamically re-weights the feature maps, thereby effectively suppressing background noise caused by semantic gaps and enhancing the model’s ability to localize landslide regions. Additionally, an edge-guided attention (EGA) module is incorporated into the decoder. This module extracts explicit edge priors from the input image using a Laplacian operator and imposes geometric constraints on the predictions via a boundary reverse attention mechanism, thereby significantly alleviating boundary ambiguity and morphological distortion of landslides. Evaluations across datasets from the Yarlung Zangbo River, Iburi-Tobu, and Bijie regions demonstrate that CETransUNet significantly outperforms state-of-the-art models—including TransUNet, SegFormer, and SwinUNet—in terms of IoU, MIoU, and F1-score. Overall, through the synergistic optimization of the coordinate attention and edge-guided attention modules, the CETransUNet model achieves synchronous enhancement of boundary integrity and geometric precision in complex scenarios, providing a reliable technical solution for large-scale intelligent landslide identification. Full article

Hyporheic zone exchange processes are strongly influenced by channel morphology, producing heat transfer patterns with distinct vertical stratification. To evaluate the effects of different channel geomorphic units on hyporheic temperature dynamics, monitoring sites were established along a segment of the Xiajiasi River (Hubei Province, China) encompassing four representative channel types: a meandering reach, a pool–riffle reach, a weir reach, and a straight reach. Hyporheic temperatures were recorded at multiple depths (0, 0.1, 0.2, and 0.3 m) during both summer and winter. The results indicate that channel morphology strongly controls the spatiotemporal distribution of hyporheic temperatures. Across all channel types, sediment temperatures exhibited depth-dependent amplitude attenuation and phase lag, with mean temperatures decreasing with depth in summer and increasing with depth in winter. The meandering reach exhibited the highest summer temperatures (28.3–30.6 °C), whereas the pool–riffle reach displayed the steepest thermal gradients (deep sediment temperatures as low as 25.6 °C). In contrast, the straight reach exhibited the weakest thermal buffering capacity. The presence of the weir markedly modified downstream thermal conditions, reducing sediment temperatures by approximately 1.6–3.2 °C during summer, whereas overall winter observations demonstrated a pronounced thermal inversion with deep sediment temperatures increasing by 1.2–2.9 °C. These findings demonstrate that distinct geomorphic units create diverse thermal niches; river managers can incorporate diverse geomorphic features into river restoration designs to create localized thermal refugia, thereby protecting temperature-sensitive aquatic species. Full article

Satellite remote sensing imagery has become an essential resource for large-scale surface water monitoring. Nevertheless, in karst regions, the elongated and fragmented morphology of water bodies, along with terrain shadows and vegetation interference, still leads to limitations in existing methods for small water body detection and accurate boundary delineation. To overcome the aforementioned issues, this paper proposes MESA-Net, a CNN–Mamba hybrid segmentation network for water body extraction in complex karst terrain. The network employs ResNet-18 as an encoder to extract shallow-level features. The decoder primarily consists of three modules: the Cross-Scale Adaptive Feature Fusion (CAFF) module, the Directional Gradient Histogram Edge-Guided Fusion (DGHEF) module, and the Omni-directional Global-Local Mamba Block (OGLMB). Among these, the CAFF module enhances the detection capability for small-scale water bodies by performing cross-scale feature fusion and dynamic weight allocation on the feature outputs from each level of the encoder. The OGLMB integrates an omnidirectional state space model with an 8-directional scanning mechanism and cross-attention guidance, effectively enhancing the ability to represent the structural continuity and global consistency of water bodies. The DGHEF utilizes directional gradient histograms to explicitly model multi-directional boundary information of water bodies, and combines this with a boundary guidance mechanism to enhance the representation of water body boundary features whilst suppressing spurious responses. In addition, the LJ-Water dataset has been constructed for the Lijiang River Basin in Guangxi, which is based on Sentinel-2 imagery. To validate the effectiveness and generalization capability of the method, comparative experiments were conducted on the self-built LJ-Water dataset as well as the publicly available Water-CD and LoveDA datasets. Experimental results demonstrate that MESA-Net consistently outperforms representative CNN-based, Transformer-based, and Mamba-based segmentation networks. On the LJ-Water dataset, it achieves 84.59% IoU and 91.65% F1, whilst on the Water-CD dataset, it attains 92.15% IoU and 95.91% F1, and 69.83% IoU and 82.24% F1 on the LoveDA dataset. Relative to the strongest baseline method, the proposed model achieved IoU gains of 1.51%, 2.34%, and 1.73% on the three datasets, respectively. In summary, MESA-Net demonstrates superior water segmentation performance under complex background conditions. Full article

Due to overfishing, eutrophication of rivers and lakes, and irrational stocking practices, the diversity of wild native carp populations has declined, leading to germplasm degradation and a decrease in fish quality, thereby affecting the sustainable development of fisheries. In this study, a novel hybrid crucian carp lineage (designated LWR) was successfully established via distant hybridization using Dongting Lake crucian carp (LC, ♀) and Hefang crucian carp (WR, ♂) as parental stocks. Systematic analyses were conducted on the morphology, ploidy, fertility, growth performance, survival rate, and molecular genetics of LWR. The results reveal that LWR is an allodiploid (2n = 100), with a chromosome number identical to that of its parents. Gonadal development in the hybrid progeny (LWR) was normal, with both sexes being fertile and reaching sexual maturity at one year of age. Morphologically, LWR exhibited intermediate traits with a paternal bias, characterized by a deep-bodied and elongated shape. In terms of growth performance, LWR displayed significant heterosis (approximately 145% and 271% higher than the body weight of the maternal parent at 6 months and 1 year). Molecular genetic analysis indicated that the 5S rDNA sequences of LWR were predominantly inherited from the paternal parent WR, with insertions, deletions, recombination, and mutations detected. The mtDNA sequences exhibited 99.78% similarity to those of the maternal parent LC, following maternal inheritance with sporadic nucleotide variations. These findings offer a new paradigm for hybridization and a theoretical foundation for the improvement and sustainable utilization of indigenous crucian carp germplasm resources, the selective breeding of improved aquaculture strains, and the sustainable development of fisheries. Full article

Anabranching, sedimentation, island growth, and bank scouring are key morphological processes occurring in the Tigris River. These processes can disrupt navigation, affect water intake, and compromise the safety of infrastructure near the riverbanks. This study aims to simulate and assess the responses of a 4.75 km meandering–anabranching reach of the Tigris River in Baghdad city center to various alternative groyne dimensions designed to control natural morphological processes, using a depth-averaged hydro-morphodynamic model (Delft3D-FM). Bathymetric and field measurements, including sediment load, velocity, water level, and discharge, were conducted and used for model calibration and validation. The model demonstrated good agreement with observed water levels (Root Mean Square Error (RMSE) = 0.02 m) and depth-averaged velocities (RMSE = 0.068–0.142 m/s), and it reproduced morphological changes with a maximum bed-level error of approximately 13% at control sections. More than 20 groyne configurations, varying in orientation, length (L), and spacing (S), were simulated and assessed. In this study, the selection of the best groyne design for controlling morphological processes in the target reach was carried out using a proposed composite Groyne Performance Index (GPI). The index is based on weighted contributions from flow partitioning, thalweg stability, cross-channel infilling, island-margin response, and corridor deposition. While the straight–groyne configuration with L = 0.25 W (river width) and S = 2 L achieved the highest GPI, the L = 0.25 W and S = 3 L configuration is selected as the preferred design as it provided a more balanced response in terms of flow redirection, thalweg stability, reduced anabranching and deposition, and lower scour risk. The adopted selection methodology demonstrates a valuable indicator-based framework for selecting river-training layouts in low-slope, sand-bed, meandering–anabranching reaches of alluvial rivers. Full article

Microplastic (MP) pollution in highly urbanized rivers poses increasing ecological risks; however, the ingestion characteristics of wild fish across urbanization gradients remain insufficiently understood. In this study, gastrointestinal suspected microplastic ingestion was investigated in a diverse fish assemblage (n = 310, 10 species) collected from core urban, intermediate urban, and suburban reaches of the Suzhou River, Shanghai. A total of 496 visually identified suspected microplastics were detected, with an overall detection rate of 71.29% and a mean abundance of 1.60 ± 1.67 items/individual. Statistical analyses revealed significant spatial variation in suspected microplastic abundance (p < 0.05), with fish from the core urban area (2.08 ± 1.77 items/individual) and intermediate urban area (1.87 ± 1.80 items/individual) exhibiting significantly higher levels than those from suburban reaches (1.27 ± 1.50 items/individual). In contrast, differences associated with feeding habits and habitat layers were not statistically significant (p > 0.05). In the indicator species Coilia nasus, gastrointestinal suspected microplastic abundance showed a significant positive correlation with both body length (R² = 0.205, p < 0.001) and body weight (R² = 0.153, p < 0.005). Morphological characterization indicated that small-sized (≤1 mm, 79.47%), transparent fibres predominated among the detected particles. Overall, these findings suggest an association between urbanization and fish suspected microplastic exposure, although downstream accumulation likely co-drives this spatial pattern. Furthermore, differences associated with specific ecological traits were not statistically significant and require further targeted investigation. This study provides baseline ecological evidence for understanding microplastic exposure in urban river ecosystems and highlights the importance of integrated long-term monitoring for ecological risk assessment and management of emerging pollutants. Full article