Search Results (65)

Introduction: Restoring riverine connectivity is a cornerstone of ecological restoration for migratory fish populations. When physical barriers like dams lack effective fishways, translocation to more suitable sites becomes an alternative. Objectives: This study aims to present a decision-support methodology based on the Fragmentation Index (FI), designed to prioritize release sites in alternative river stretches that maximize the likelihood of survival of translocated diadromous fish. Methodology: The method integrates field-based obstacle characterization and transposability classification, together with a weighted penalty for restrictive obstacles located closer to the confluence with the main stem. The methodology was applied to six tributaries of the Douro River, targeting the European eel (Anguilla anguilla). Results: The FI successfully distinguished between functional reaches and severely fragmented systems. Results revealed high heterogeneity among the studied tributaries, with the Távora (FI = 1.07) and Ceira (FI = 1.12) Rivers identified as top priorities due to low fragmentation and stable hydrology. In contrast, the Tedo River (FI = 5.18) illustrates index’s sensitivity. Despite a high barrier density, its downstream stretch of ~14 km remains functionally connected because the first restrictive obstacles are located far upstream from the confluence. Conversely, the Torto River (FI = 0) was excluded due to severe drought conditions, underscoring the need to pair connectivity metrics with hydrologic viability. Conclusions: For large-scale translocations, this framework enables distributing fish across multiple systems to safeguard the ecological integrity of recipient communities while ensuring individuals can successfully complete their life cycles. Overall, this approach provides a quantitative and replicable framework for managing endangered species by prioritizing release sites with high longitudinal connectivity. Full article

Introduction: AQUArestore is a three-year project focused on promoting adaptive ecological restoration strategies for river ecosystems in the vulnerable cross-border region of Portugal. The project responds to pressing environmental challenges across the territory, including severe habitat degradation, climate vulnerability, declining water security, and biodiversity loss, with particular concern for freshwater fish communities, making river restoration essential to preserve native species and freshwater ecosystem services. Objective: The project aims to develop a replicable framework for restoration of Mediterranean transboundary riverine habitats, supporting the objectives of the EU Nature Restoration Law (NRL, Regulation 2024/1991). The consortium AQUArestore will develop (1) robust restoration indicators, (2) implement living labs for restoration experimentation, and (3) establish capacity-building and training programs for technicians and citizens. Methodology: The project kick-off meeting was used to operationalize project tasks, detail the implementation calendar and milestones, and clarify responsibilities of each project member and partner institutions within the different work tasks. The meeting gathered consortium members from the coordinating institution CEF-ISA (researchers at the Instituto Superior de Agronomia) and partners WWF Portugal (an environmental NGO) and Mushmore Cooperative, each one contributing according to their respective expertise and institutional objectives. Results: The AQUArestore project kick-off meeting took place in January 2026 at ISA, Lisbon, and included a presentation of the NRL and a detailed discussion of project task development. In detail, the activities will begin with the compilation of information on previously restored sites (Task 1). This will support the development and validation of environmental and biodiversity indicators of restoration outcomes, including those linked to freshwater fish assemblages and riparian vegetation (Task 2). The project will then establish two living labs as platforms to test nature-based solutions in collaboration with stakeholders and local communities (Task 3). In parallel, AQUArestore will strengthen technical capacity through training for practitioners and public authorities (Task 4). Finally, dissemination will be supported through citizen science, communication activities, and stakeholder engagement, fostering a broader impact (Task 5). Together, these tasks provide an integrated, science-based, and participatory framework aiming to support adaptive river restoration under climate and environmental changes. Conclusions: By integrating ecological restoration, biodiversity and environmental monitoring, and stakeholder engagement, AQUArestore is expected to contribute to the recovery of Mediterranean freshwater ecosystems and improve habitat quality and connectivity for native fish communities, enhancing resilience to climate change and other anthropogenic pressures. Full article

Suspended particulate matter (SPM) is a key environmental driver in aquatic ecosystems and plays a significant role in shaping microbial communities, particularly in sediment-rich rivers. Dam construction alters hydrological regimes and creates distinct SPM gradients; however, the response mechanisms of microeukaryotic plankton communities remain poorly understood. In this study, we used 18S rRNA gene high-throughput sequencing to characterize microeukaryotic plankton communities across riverine, lacustrine, and transitional zones of the Xiaolangdi Reservoir on the Yellow River (China). Our results revealed distinct community compositions in the lacustrine zone, with SPM identified as the primary factor driving community differentiation. Alpha diversity was highest in the riverine zone, while beta diversity differences among zones were dominated by species turnover. Dominant taxa included Cryptophyta (44.71% ± 30.79%), Metazoa (18.98% ± 17.71%), Perkinsea (7.97% ± 9.78%), Chlorophyta (7.06% ± 5.80%), and Dinophyta (6.06% ± 6.73%). Metazoa, Dinophyta, and Phaeophyta were enriched in high-SPM riverine waters, whereas Alveolata dominated low-SPM lacustrine zones. Community assembly was primarily deterministic, governed mainly by homogeneous selection, with stochastic processes exerting stronger influence in riverine zones. Network analysis indicated that riverine zones exhibited more complex and stable networks, lacustrine zones showed higher local but lower global connectivity, and transitional zones displayed stronger interactions but lower stability. These findings advance our understanding of microeukaryotic plankton responses to dam-induced environmental changes and provide a basis for assessing biodiversity impacts in regulated river systems. Full article

River ecological restoration in lowland plain basins is often constrained by fragmented river networks, degraded riparian zones, eutrophication risk, and intensive human disturbance. Conventional monitoring approaches rarely connect watershed-scale dynamics with responses from typical restoration units, limiting quantitative evaluation and the separation of direct project outcomes from broader environmental variability. To address this gap, this study developed a collaborative satellite–unmanned aerial vehicle (UAV)–unmanned surface vehicle (USV) monitoring framework and applied it to the Nihe River Basin, China, a lowland plain river undergoing systematic restoration under the Shan-shui Initiative. The framework combines Sentinel-2 time-series imagery, high-resolution Gaofen-1, Gaofen-2, and Jilin-1 imagery, UAV orthophotos, USV observations, and auxiliary environmental datasets. Unlike single-scale monitoring approaches, it links watershed-scale indicators, including water-body dynamics, chlorophyll-related eutrophication risk, riparian ecological background, and soil-water conservation capacity, with unit-scale diagnosis of riparian buffer and riverine wetland restoration. Results showed that river water-body area increased from 37.78 km² to 40.59 km² during 2021–2024, while normalized difference chlorophyll index (NDCI)-based eutrophication risk improved in 9.12% of the monitored river area and degraded in only 0.47%. Riparian vegetation cover remained high, whereas regional soil-water conservation capacity declined due to climatic factors, revealing asynchronous responses between local recovery and regional background conditions. At the unit scale, riparian buffer restoration enhanced buffer continuity and near-bank water quality, as reflected by decreased chemical oxygen demand (COD), increased dissolved oxygen (DO), and limited ammonia nitrogen (NH₃-N) improvement. Riverine wetland restoration promoted land-use adjustment and ecological spatial reorganization. This cross-scale evidence chain supports adaptive management of inland river and wetland restoration projects. Full article

In situ leaching is increasingly used for rare earth element (REE) extraction because of its operational efficiency; however, acidic and chemically reactive leaching solutions may generate substantial environmental risks in riverine systems. This study evaluated water contamination and screening-level ecological risk following a cyanide leakage incident associated with a pilot REE mining operation in Houaphanh Province, northern Lao PDR. Surface water samples were collected from 12 downstream monitoring locations between February and April 2024. Physicochemical parameters, free cyanide (CN⁻), and dissolved metals, including arsenic (As), lead (Pb), copper (Cu), manganese (Mn), aluminum (Al), zinc (Zn), and iron (Fe), were analyzed using portable multiparameter probes, colorimetric cyanide determination, and ICP-OES. Contamination severity was interpreted using Pollution Index (PI) and Hazard Quotient (HQ) indicators based on Lao national standards and international guideline values. Results showed severe downstream contamination, with free cyanide and several dissolved metals substantially exceeding permissible thresholds. Observed elevated concentrations of As (30.29 mg/L), Pb (10.38 mg/L), Cu (14.97 mg/L), and CN⁻ (0.51 mg/L) indicated elevated ecological risk conditions, while acidic pH conditions may have enhanced metal mobilization and downstream transport. Descriptive spatial observations indicated apparent downstream contaminant dispersion within affected downstream river communities reliant on river water for domestic use, irrigation, and fisheries. Field observations additionally documented fish mortality, reduced irrigation usability, and deterioration of river water quality conditions in affected downstream communities. The findings suggest the potential vulnerability of Mekong-connected river systems to chemically intensive REE extraction activities and highlight the importance of preventive environmental governance, continuous monitoring, and operational risk management in emerging rare earth mining regions. Full article

Riverine and pluvial flooding triggered by extreme monsoon rainfall is intensifying under climate change, yet flood-risk products in many coastal municipalities remain too coarse for parcel-scale prevention and climate-adaptive planning. This study presents a 1 m LiDAR–GIS flood susceptibility framework validated against consecutive record-breaking floods in Dangjin City, South Korea (July 2024: 214.6 mm; July 2025: 377.4 mm). Five terrain parameters—elevation, slope, topographic wetness index, flow accumulation, and distance to stream—were integrated into a weighted Flood Susceptibility Index ($\mathrm{FSI}=0.20\cdot \widehat{E}+0.30\cdot \widehat{S}+0.25\cdot \widehat{T}+0.15\cdot \widehat{F}+0.10\cdot \widehat{D}$) and classified into four risk strata using K-means clustering (k = 4), identifying a high-risk zone of 0.3119 km² (5.00% of the 6.18 km² analysis domain). A Monte Carlo sensitivity analysis (n = 5000; ±0.10 weight perturbation) confirmed classification robustness (CV = 5.21%, mean Pearson r = 0.992). Static bathtub inundation scenarios (Δh = 0.5–2.0 m above the 5th-percentile baseline elevation of 13.29 m AMSL) produced footprint expansion from 0.370 to 0.572 km², capturing all nine observed flood inventory points at the 2.0 m threshold, with flow-connectivity analysis confirming that 91.7–93.1% of predicted inundation is hydraulically connected to the D8-derived stream network. Spatial validation yielded a combined IoU of 6.51%, with a progressive increase from 3.33% (2024) to 6.50% (2025) confirming that the FSI correctly tracks flood-extent expansion with increasing rainfall intensity. Relying exclusively on topographic data and standard GIS algorithms, the framework supports scientifically grounded flood risk governance in data-limited municipalities, directly aligned with SDG 11, SDG 13, and Sendai Framework Target B. Full article

Extreme hydro-meteorological events are intensifying under climate change, disproportionately disrupting last-mile healthcare in flood-prone geographies. In this study, flood-adaptive primary care clinics (FAPCCs) integrated with islandable smart microgrids and a rapid-deploy medical technology stack (MedTech) are developed and evaluated to ensure continuity of essential services (triage, maternal and child health, vaccination cold-chain, minor procedures, diagnostics, and telemedicine) during fluvial, pluvial, and coastal flooding. Evidence on resilient health facilities, microgrid architectures, distributed energy resources, and modular clinical systems is presented in a multi-layer systems design: (1) a modular, amphibious, and elevatable clinic chassis; (2) a photovoltaic–battery–diesel hybrid system with demand-aware energy management; (3) redundant connectivity long-term evolution/fifth-generation, satellite, and very high frequency; (4) a rapid-deploy MedTech kit including point-of-care diagnostics, low-temperature cold-chain, negative-pressure isolation, and sterilization modules; and (5) flood-aware logistics using unmanned aerial vehicle/unmanned surface vehicle. A mixed-integer linear programming sizing is formulated and dispatched with a continuity-of-care reliability metric that couples energy availability to clinical throughput. Simulation across three archetypal sites (peri-urban delta, inland riverine, coastal estuary) shows that FAPCCs achieve the service availability of higher than 99.5% across 7-day grid outage scenarios while reducing fuel use by 62–81% relative to diesel-only baselines, maintaining vaccine temperatures within 2–8 °C with <0.1% thermal excursion time, and sustaining telemedicine quality of service with <150 ms median uplink latency in hybrid networks. A life-cycle cost analysis indicates a 7.1–9.8 year discounted payback from fuel displacement and avoided service loss. Deployment playbooks and policy guidance are also proposed for Ministries of Health and Disaster Agencies in monsoon-impacted regions. Full article

While harmful cyanobacterial blooms (HCBs) are extensively characterized in eutrophic lakes, the ecological dynamics of connected river networks remain oversimplified, obscuring the mechanisms of community assembly and toxin distribution across the lake–river interface. This study investigated the spatial heterogeneity of HCBs and microcystins (MCs) in the Lake Taihu watershed, revealing a complex functional divergence between lotic and lentic ecosystems. The rivers functioned as primary nutrient sources, with Total Nitrogen (3.35 ± 1.52 mg·L⁻¹) and Total Phosphorus (0.21 ± 0.22 mg·L⁻¹) concentrations being 1.7-fold and 1.8-fold higher, respectively, than those in the lake during peak periods. Conversely, the lake acted as a biological sink, supporting a peak cyanobacterial density (3.32 × 10⁷ cells·L⁻¹) nearly 1.5 times that of the river network. Phytoplankton community analysis revealed distinct ecological niches: while the lentic lake environment was almost exclusively dominated by colonial Microcystis (>90% relative abundance), the lotic river networks harbored a diverse assemblage with significant contributions from filamentous Oscillatoria and Dolichospermum. Correspondingly, intracellular MC (IMC) in the lake (up to 14.5 μg·L⁻¹) significantly exceeded riverine levels (generally <1.0 μg·L⁻¹). Despite these compositional differences, toxin dynamics exhibited strong bidirectional coupling (r > 0.75, p < 0.01), suggesting a spillover effect where the lake determines the watershed’s toxin burden during rivers outflow period. Redundancy Analysis (RDA) further elucidated that limnetic blooms were primarily regulated by water temperature and pH, whereas riverine communities were strictly constrained by hydrodynamic flow. Consequently, the health risk assessment revealed a highly heterogeneous landscape where, beyond the northern lake bays, specific semi-lentic river segments emerged as cryptic hotspots. These findings demonstrate that while nutrients fuel the system, hydrodynamic conditions act as the ultimate ecological filter determining the spatiotemporal distribution of cyanobacterial risks, necessitating an integrated approach to monitoring the entire lake–river continuum. Full article

Understanding patterns of genetic diversity and population structure in freshwater fishes is crucial for evolutionary studies and conservation planning. Tor tambra is a common freshwater fish species in Thai waters, yet its genetic diversity and population connectivity remain largely unexplored. This study investigated the phylogeographic structure and genetic diversity of Thai T. tambra through phylogenetic analyses and molecular approaches using mitochondrial DNA markers (COI and Cytb). Our analyses revealed four distinct genetic lineages (clades A-D) within Thai T. tambra. Lineage C comprised specimens from southern Thailand, Malaysia, Indonesia, and southern China, while lineages A, B, and D were distributed exclusively within Thailand. These Thai-endemic lineages exhibited pronounced geographic structuring across northern and western regions, with lineage A widespread, lineage B confined to northern areas, and lineage D restricted to western localities. The genetic differentiation and distribution patterns of these lineages suggest influence from the limited north–south river system connections and the biogeographic barrier posed by the Isthmus of Kra. Multiple lineages co-occurred at some locations, indicating a complex evolutionary history. These findings provide important implications for understanding the evolutionary processes and biogeographic factors shaping genetic diversity within T. tambra across the riverine systems of Thailand. Full article

Data on microplastic contamination in pristine caves are rare, thus limiting our understanding of its pervasiveness in intact underground ecosystems. Here, we quantified microplastics in sediments from two newly discovered, extremely remote caves (Maucci and Luftloch) and compared them with a frequently visited cave (Trebiciano), all three of which are hydraulically connected to the Reka/Timavo River in the Classic Karst (NE Italy). Sediment samples were collected along river-to-slope transects and analyzed for microplastics using density separation and μFT-IR spectroscopy. Average contamination levels were comparable across caves, ranging from 84.7 to 105.9 items kg⁻¹ (dry weight). Fibers and fragments dominated, with similar polymer spectra across sites—polypropylene (PP, 29–42%), polyethylene (PE, 19–27%), and polyethylene terephthalate (PET, 33–46%). Microplastic abundance systematically increased with elevation, up to ~4–12× from river-proximal to high-bench sediments. Polymer-resolved trends reflected density-coupled, flood-driven sorting with low-density PP and PE accumulated on higher benches and denser PET depleted aloft, indicating slackwater retention at flood crests and re-entrainment of lower benches during recession. These findings suggest that indirect riverine inputs of microplastics outweigh direct human contamination and provide the first baseline for pristine Timavo caves—serving as reference sites for background microplastic levels in the Classic Karst and similar karst systems worldwide. Full article

The recent recognition of the Neotropical otter (Lontra annectens) as a distinct species highlights the need to evaluate its genetic status and connectivity across fragmented tropical habitats. We analyzed genetic diversity, population structure, and recent demographic patterns of L. annectens from two contrasting regions in northern Costa Rica—Tortuguero National Park (TNP) and the Sarapiquí River Basin (SRB). Non-invasive fecal and anal-gland secretion samples collected during 2021–2022 were genotyped at ten nuclear DNA microsatellite loci. Genetic diversity was moderate across regions (mean allelic richness [AR] = 3.98–4.03, observed heterozygosity [Ho] = 0.52–0.58), expected heterozygosity [He] = 0.62–0.65) with no significant inter-regional differences. Bayesian clustering, principal component analysis, and pairwise F_ST (0.002) supported a near-panmictic population. Kinship analyses detected localized clusters of related individuals, suggesting weak but non-random structuring, while contemporary migration estimates indicated low-frequency, asymmetric gene flow from SRB to TNP. Bottleneck tests revealed signatures of recent demographic contraction in both regions, particularly in TNP. These findings demonstrate limited yet ongoing connectivity among riverine subpopulations and emphasize that increasing habitat fragmentation could erode this exchange. Maintaining hydrological corridors and monitoring genetically vulnerable subpopulations should be conservation priorities to preserve gene flow and long-term viability of L. annectens in northern Costa Rica. Full article

Land use change driven by accelerated urbanization in Mongolia has precipitated significant degradation of urban riverine ecosystems over the past two decades. This study investigates hydrological transformations in the Selbe River Catchment of Ulaanbaatar, a cold semi-arid urban system undergoing intensive densification. Using the Site-scale Urban Water Mass Balance Assessment (SUWMBA) framework, we quantified water cycle dynamics across four temporal intervals (2008, 2010, 2018, and 2023), capturing shifts in surface runoff, infiltration, and evapotranspiration associated with land use transitions. Calibration and validation employed discharge records from the Selbe-Dambadarjaa gauging station. Results show that total inflows increased from 223 to 312 mm between 2008 and 2023, driven by a more than twentyfold rise in imported water (from 1 to 22 mm). Evapotranspiration declined by roughly one-third, while infiltration displayed a threshold-type non-linear response—rising sharply between 2010 and 2018 before decreasing again in 2023 as imperviousness intensified. Model performance weakened after 2018, underscoring the limitations of conventional hydrological frameworks in rapidly urbanizing contexts. A redevelopment scenario for the Selbe Sub-Center, aligned with the Ulaanbaatar City Master Plan 2040, projected substantially reduced evapotranspiration (132 mm) and markedly increased stormwater runoff (270 mm), reflecting expanded impervious cover and diminished vegetation. Imported water and wastewater flows (each 386 mm) also increased due to full connection to centralized supply and sewerage infrastructure, indicating a shift toward engineered water pathways and reduced hydrological connectivity to the Selbe River. These findings highlight the urgency of water-sensitive urban design and provide evidence directly informing Mongolia’s 2040 Urban Master Plan and decentralization strategy. The study establishes methodological precedent for applying SUWMBA to cold, semi-arid catchments and contributes quantitative insights for integrated land–water management policies. Full article

Accurate information regarding species boundaries is essential for ecological research and conservation planning. This information is particularly difficult to obtain but essential for cryptic amphibian species. The distribution and potential dispersal corridors of two cryptic salamander species, the Korean clawed (Onychodactylus koreanus) and the Yangsan clawed (O. sillanus) salamanders, were investigated using integrated approaches for high-resolution species distribution modeling (SDM), genetic species identification, and habitat connectivity analysis. The SDM results showed high habitat suitability in mid- and high-mountainous areas, but very low suitability in riverine areas for both species. Genetic species identification of the 25 populations delimited the distribution boundary between the two species along the Nakdong and Geumho rivers. Dispersal corridors of the two species commonly involved a detour around the major rivers and produced only one possible dispersal route, where both species moved into the opposite species’ habitat along the east side of the mountainous areas of the Geumho River. The findings not only clarify the distribution range of two cryptic Onychodactylus species in the Republic of Korea but also highlight the importance of the unique dispersal route for studying species interactions and maintaining ecological connectivity. Full article

Microplastic pollution in riverine ecosystems poses critical environmental challenges, yet current modeling approaches inadequately capture the spatial heterogeneity and topological complexity of fluvial systems. This study develops an innovative spatiotemporal graph convolutional network (ST-GCN) framework that integrates hydrological connectivity, flow parameters, and microplastic characteristics for simultaneous migration pathway identification and pollution source tracing. This model constructs multi-scale graph representations encoding system structure and transport dynamics, implements spatial-temporal convolution layers with adaptive attention mechanisms, and employs a backpropagation-based algorithm for inverse source identification. Validation using 18 months of field observations from 45 monitoring nodes across a 127 km river reach demonstrates 87.3% pathway prediction accuracy and 94.3% source localization accuracy (R² = 0.841, p < 0.001), representing substantial improvements over conventional advection–diffusion models. The framework successfully identified three pollution sources during a real contamination incident within 6 h of detection, enabling rapid regulatory intervention. This research advances environmental modeling by demonstrating that graph neural networks effectively capture transport processes in networked hydrological systems, providing practical tools for watershed management and evidence-based pollution control decision-making. Full article

In Calabria coastal regions, seaward and landward sides could be connected through the ecological role of fluvial catchments. Calabria Tyrrhenian coast shows a wilderness area, characterized by two terrestrial and marine Special Areas of Conservation (SACs) connected by the fluvial catchment of Verri stream. The bibliographic search was realized according to a Preferred Reporting Items for Systematic Reviews and Meta-Analysis, as a standardized method for screening the most relevant literature. The field survey, conducted in the study area, highlighted high biodiversity levels and a great natural heritage represented by 189 plant species and 130 animal ones. According to the resulting data, the basin represents a classical model of ecological corridor linking terrestrial and marine SACs, as cornerstones of Natura 2000 network, so representing the European assessment for biodiversity conservation. This paper highlights the high biological richness of a wilderness area showing the tight relationship between the continental and the marine districts of the same coastal region. The main goal of the research is to remark the fundamental role of fluvial corridors within a regional approach where riverine catchments could represent the connecting steps of the network. In Calabria it is hopeful to establish a functional connectivity amongst protected areas supported by fluvial corridors along the regional basins. Full article