Search Results (1,299)

The Wadi Al-Ahsaba watershed is an arid to semi-arid catchment situated in southwestern Saudi Arabia, characterized by intermittent surface flow, high evaporation and low rainfall, and a dam reservoir built for flood control. The work aims to assess hydrological and anthropogenic controls on surface and groundwater quality, pollution status, and human health risks using an integrated approach of hydrogeochemical analysis, multivariable statistics, and water quality and contamination indices. A total of 21 water samples (15 surface water, 6 groundwater) were analyzed for general chemistry, major ions, and trace elements. Hydrogeochemical analysis and principal component analysis (PCA) were implemented to differentiate the geogenic from anthropogenic control on water quality. The pollution status and associated risk were evaluated using water quality index (WQI), contamination degree (Cd), Hazard Quotient (HQ), and Hazard Index (HI). Results suggest limited surface–groundwater interaction, with surface water dominated by Ca–Mg–HCO₃ facies, indicating recent recharge and limited water–rock interaction, whereas groundwater exhibits mixed Ca–Mg–Cl and Ca–Na–Cl–SO₄ types, revealing longer residence time and water–rock interaction. Nitrate (9.5–109 mg/L) and TDS (522–1003 mg/L) exceeded drinking water standards in 90% and 95% of tested samples, respectively, and WQI ranged from 43 to 134, reflecting excellent to poor water. High non-carcinogenic risk from nitrate was observed, especially for infants. The study concluded that the geogenic processes (water–rock interaction, evaporation, and mineral dissolution) control the general chemistry of tested water, while anthropogenic input from wastewater and agriculture input are likely contributors to nitrate contamination. The study contributes to the understanding of arid wadi-dam systems by revealing how limited recharge, hydrological connectivity, and episodic flow control contaminant transport and persistence, underscoring the critical role of integrated hydrological analysis and land use management in safeguarding freshwater resources in arid environments. Full article

Introduction: The circum-Mediterranean region is a global biodiversity hotspot, hosting a highly distinctive freshwater fauna with a high degree of endemism and conservation concern. However, these ecosystems are increasingly threatened by biological invasions, particularly by non-native fish species, which represent a major driver of biodiversity loss. Objective: This study aims to compile a comprehensive and updated inventory of non-native inland fish species across the circum-Mediterranean region and to identify the main taxonomic, biogeographical, and socio-environmental drivers shaping their distribution. Methodology: We conducted an extensive review of the scientific literature, online databases (including EASIN, GISD, and CABI), and technical reports to compile records of non-native fish species across inland and transitional waters of Mediterranean-climate basins. Analyses focused on species composition, taxonomic representativeness, introduction pathways, native regions, and the relationship between species richness and selected environmental and socio-economic variables. Results: A total of 151 non-native fish species were recorded across the study area. Italy, Spain, Bosnia and Herzegovina, France, and Croatia exhibited the highest numbers of established species. Taxonomic representation was uneven, with Salmoniformes and Esociformes overrepresented among established non-native species, while Siluriformes and Characiformes were underrepresented. Most introductions originated from Europe, Asia, and North America, primarily through intentional releases and escape events. Non-native species richness was positively correlated with gross domestic product, precipitation, and the number of dams, highlighting the role of economic development and habitat modification in facilitating invasions. Conclusions: Biological invasions by non-native fishes are widespread across the Mediterranean basin and are strongly driven by human activities and environmental conditions. The high invasion levels observed in this biodiversity hotspot pose a significant threat to endemic freshwater faunas. These findings underscore the need for coordinated transnational management strategies, stricter regulation of introduction pathways, and prioritization of high-risk species to mitigate further impacts. Full article

The Iberian barbel (Luciobarbus bocagei Steindachner, 1864) is a potamodromous species that displays migratory movements, with adults moving upstream during spring to spawn, followed by downstream migration in autumn by both adults and juveniles to feed and inhabit more productive river stretches. Increasing river fragmentation due to dam construction and operation causes a loss of connectivity and suitable habitat, which can affect this natural behaviour. In a tributary of River Douro, River Tua, a 108 m high dam, was recently built (i.e., Foz Tua dam in 2017) at only 1.1 km from the river mouth, leaving the upstream spawning area inaccessible. To evaluate the species behavioural response to this impact, a passive acoustic telemetry array was deployed in the study area, and between 2018 and 2023, 120 tagged fish had their movements tracked. The results showed two different behavioural profiles in the same population with migratory (42.5%) and resident (54.0%) individuals. During this period, a specific experimental study was developed to evaluate the response of a subset of 90 fish, captured upstream of the Foz Tua dam and translocated to an alternative downstream Douro tributary (River Pinhão, ~20 km downstream from River Tua). From these, 66.7% remained at the release site, whilst 23.3% returned to the river of origin, i.e., River Tua. From the returned fraction, 28.6% of the tagged fish maintained this migratory behaviour between both rivers in the following years. Generalized Additive Models were used for each of the two behavioural profiles observed in this study, to identify which environmental variables were associated with the presence of the tagged barbels downstream the Foz Tua dam. Ecological flow, temperature and day-period were some of the predictors explaining the use of this river stretch downstream of Foz Tua dam. This study substantially updates the available information regarding this species’ movement patterns at large spatial and temporal scales, contributing to enhancement of management and conservation programs for potamodromous species, in highly impounded and fragmented rivers. Full article

Introduction: Artificial infrastructure interrupts river longitudinal connectivity, preventing the free flow of water, matter, energy, and organisms through the system, altering the habitat and impacting freshwater biodiversity. Freshwater fishes are especially sensitive to this threat, since they are constrained to the limits of the river network. Transversal obstacles, such as dams and weirs, hinder their movements upstream and downstream and fragment populations. Longitudinal connectivity can be simply measured as the proportion of connected river length in a basin. However, other indices have been suggested more recently, measuring connectivity as the proportion of connected elements of interest (e.g., populations of a species) in a river basin. Objective: The aim of this work was to study (1) the degree of connectivity of native freshwater fish species populations in eleven Spanish river basins and (2) the impact of artificial river fragmentation in these basins on population connectivity. Methodology: Fish populations’ location and size were estimated through sampling presence data, and completed using the predicted occurrence of each species in a river basin, calculated through Species Distribution Models (SDMs). To estimate the degree of connectivity between populations of each species, the Population Connectivity Index (PCI) was calculated under two scenarios: the “current” scenario, considering all the artificial obstacles fragmenting the river network and their specific passabilities, and the “natural” scenario, considering that all the artificial obstacles in the river network were completely passable. Results: Native freshwater fish populations are severely fragmented in Spanish rivers, with a mean current PCI of 9.8% across species and river basins. The impact of artificial fragmentation is high, causing a mean decrease in PCI of 52 percentage points across species and river basins. Moreover, although the impact of artificial river fragmentation is high in all river basins, it is important to point out that there are significant differences between river basins attributed to their size and the specific traits of the ichthyofauna inhabiting them. Conclusions: The degree of connectivity in a river basin varies depending on the elements of interest considered. Therefore, incorporating ichthyofauna into the decision-making process is essential to improve the effectiveness of river restoration actions. Full article

This study investigated the associations among dam lactation number, passive immunity transfer, internal parasite burden, and weaning performance in female calves. Early consumption of high-quality colostrum is critical for effective passive immunity transfer, calf health, and long-term productivity. Colostrum composition may vary with management practices and dam lactation number, potentially influencing immunity and disease susceptibility. Forty-five cows and their female offspring (n = 45) were allocated to three groups by lactation number: first lactation (LAC1), second lactation (LAC2), and third lactation (LAC3) (15 cows and 15 calves per group). Calf birth weight was recorded. Colostrum immunoglobulin G (IgG) concentration was measured using a colostrometer and refractometer, and chemical composition (fat, protein, and non-fat solids) was analyzed. Fecal samples collected at 30, 60, and 90 days of age were examined for Eimeria spp. Colostrum IgG concentration, °Brix percentage, specific gravity, and non-fat solids did not differ among lactation groups (p > 0.05). LAC3 cows had higher colostrum protein content, while LAC1 cows had greater fat concentration (p < 0.05). Calves from LAC1 dams were lighter at birth than those from LAC2 and LAC3 dams (p < 0.001). The prevalence of Eimeria spp. was not influenced by lactation number, birth weight, or colostrum quality (p > 0.05), but treatment costs were higher in calves from LAC3 dams (p < 0.01). In conclusion, lactation number affected colostrum composition and calf growth but did not alter IgG concentration, underscoring the importance of effective colostrum management to improve calf performance and dairy system sustainability. Full article

Occupational stress in dentistry, particularly during endodontic procedures, impacts practitioners’ health and performance. This study introduces a novel approach using real-time Heart Rate (HR) data from Apple Watch technology to assess physiological responses potentially indicative of occupational stress among endodontists. Materials and Methods: Twelve endodontists participated in this study, treating 119 patients. In a controlled clinical environment, HR was continuously monitored with the Apple Watch, and data were recorded via the Cardiogram app, capturing HR variations across treatment stages. Results: Significant HR fluctuations were observed during procedurally demanding stages such as local anesthesia and rubber dam placement. The endodontist’s HR, as a physiological proxy for stress, was significantly influenced by the treatment difficulty level, stage, and the patient’s age. Conclusions: Using Apple Watch technology, our study revealed significant HR variations during different endodontic treatment stages, suggesting fluctuating physiological responses that may reflect occupational stress. Elevated HR was noted during patient examination and rubber dam placement, particularly in complex cases. These preliminary findings suggest that HR monitoring via wearable technology may serve as a useful, albeit indirect, indicator of occupational stress during endodontic procedures. Future studies with larger samples and additional validated stress biomarkers are needed to confirm these observations. 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

Introduction: Freshwater ecosystems are among the most threatened worldwide, with river fragmentation, primarily caused by dams and weirs, identified as a major driver of biodiversity loss. This issue is particularly acute in Europe, where more than one million instream barriers disrupt longitudinal connectivity and compromise the movement of migratory fish. Fishways are widely implemented to mitigate these impacts, yet attraction efficiency at fishway entrances remains poorly understood, especially for Iberian potamodromous cyprinids, a group facing severe conservation pressures. Objective: This study aims to investigate how hydraulic conditions and social context influence the attraction and passage behavior of Luciobarbus bocagei, a rheophilic potamodromous cyprinid endemic to the Iberian Peninsula, in an experimental Vertical slot fishway (VSF) entrance. Methodology: Experiments were conducted in a controlled flume equipped with a VSF entrance design. Two hydraulic scenarios were tested, a Low Head Drop (LD) and a High Head Drop (HD), under a constant discharge of 34 L/s. A computational fluid dynamics (CFD) model was used to characterize and compare the flow field hydrodynamics. Fish were tested individually and in groups of three to assess the role of social dynamics. The metrics collected included time to first approach, first attempt, time to first successful passage, attraction efficiency, and passage efficiency. Cox proportional hazards models were applied to evaluate treatment effects. Results: Preliminary results showed that social context influenced fish attraction behavior. In the two hydraulic scenarios, individuals tested alone tend to exhibit lower likelihoods of approaching, attempting, and successfully negotiating the fishway compared to fish in schools. Delays were also evident for attempts and successful passages, with LD_Ind performing the worst. Conclusions: These findings highlight the importance of hydraulic conditions and social behavior in shaping attraction efficiency. They underscore the need to integrate species-specific behavioral ecology into fishway design, operation, and attraction assessment, acknowledging that fish attractivity is influenced by environmental and ecological factors beyond fishway structure, particularly in Mediterranean river systems where fragmentation pressures are high and potamodromous cyprinids are at risk. Full article

LIFE REVIVE aims to restore ecological status and ecosystem services in the Lima and Vouga river basins (NW Iberian Peninsula), where hydromorphological alteration and hydropower-driven flow regulation are major causes of water bodies failing to reach Good Ecological Status under the EU WFD. The project targets key pressures such as longitudinal fragmentation by weirs and dams, artificial flow regimes, degradation of spawning substrates, and the spread of invasive aquatic plants, which strongly affect fish communities, including sea lamprey, salmonids, and other diadromous species. Technically, the project combines barrier removal or eco-adaptation, nature-like fish passes, and spawning-habitat renaturalisation with optimized environmental flow regimes (EFR) downstream of important hydropower systems, explicitly accounting for present and future hydroclimatic scenarios. Multi-scale ecohydrological modelling (species distribution models, habitat suitability models, GLM/GAM approaches) will quantify fish–flow–habitat relationships and support the definition of operational EFR guidelines that balance ecological requirements with hydropower and agricultural constraints through joint work with the main Portuguese hydropower operator, EDP. Impact evaluation is structured around a rigorous BACI monitoring design in intervention and control tributaries, using standard WFD biological indices for fish and aquatic/riparian vegetation, hydromorphological indices (HQA, HMS, RHS), and project-specific Key Performance Indicators for water quality, biodiversity, and habitat. Expected outcomes include the restoration of at least 51 km of rivers towards free-flowing conditions, reduced hydromorphological pressure in more than 20 km of heavily modified river stretches, and measurable increases in the distribution and abundance of fish species and native vegetation. A strong communication and capacity-building programme underpins public engagement, while a decision matrix for barrier prioritization, technical workshops, and pilot replications in additional basins (e.g., Alva, Mouro, Deva, and Tea in Galicia) are designed to maximize transferability, policy uptake, and long-term sustainability of the solutions beyond the project lifetime. Full article

Introduction: Freshwater systems are increasingly being impacted by a plethora of pressures. Freshwater fish are thus periled, urging the need to investigate the drivers of population decrease to better counteract them, in order to provide some conservation relief to these pressured species. Methodology: To facilitate freshwater research, the Dammed Fish Project developed a series of free tools that simplify procedures and facilitate the access of correct data. Results: RivTool+ is a free software that evolved from RivTool (used in over 75 countries) and that integrates new functions and acts as a tool hub to host additional software apps. The computing engine of RivTool, that allows along the river network calculations and summarizations, is now able to be used by new tools. RivConnect—River network connectivity app that allows graph-based quantification of structural and functional connectivity, using several metrics and understanding network directionality. RivFish—App that contains the corrected, spatially and taxonomically, occurrence, at the basin and sub-basin level, of more than 600 native freshwater fish species of Europe. RivOpt—Optimization tool that allows for river network connectivity restoration optimization. RivOpt accounts for conflicting multiple objectives and is able to deal with different restoration actions for each barrier (removal, partial removal, fishway construction and retrofitting or no action). Conclusions: Dammed Fish tools facilitate research procedures and access to verified data, improving the information baseline, increasing the accuracy of results and accelerating research. Thus, it contributes to an improved understanding of the mechanisms controlling species vulnerability and contributes to their conservation. Full article

This study develops an integrated computational framework to assess the passage efficiency of a dam crest serving as a critical inter-regional corridor following a severe explosion event. The framework combines a physics-based damage model with an agent-based cellular automata (CA) approach that incorporates pedestrian behavioral heterogeneity. The damage model conceptualizes three concentric zones: a complete fragmentation zone (0–1.5 m) with total material disintegration, a primary damage zone (1.5–5 m) following an exponential decay in structural integrity, and a secondary damage zone (5–20 m) governed by a power-law attenuation of fragmentation effects. Pedestrian behavior is parameterized by the Allowable Conflict Coefficient (ACC), the inverse of interpersonal friction, and the Emergency Level (EL), which scales the desired velocity. Extensive simulations under stochastic and targeted impact scenarios reveal a consistent evacuation performance hierarchy: Center (C) > Bottom-Left (BL) > Top-Left (TL) > Bottom-Right (BR) ≈ Top-Right (TR). Exit-proximal damage (TR, BR) increased evacuation time by up to 85% compared with central impacts. Results demonstrate a strong coupling between physical friction and urgency: the “faster-is-faster” effect is maximized under low friction (high ACC), while high friction not only suppresses the benefits of elevated EL but can also induce “faster-is-slower” phenomena under extreme conditions. These findings underscore that optimal evacuation strategies depend critically on both impact location and crowd behavior management, providing actionable insights for emergency planning and highlighting the importance of conflict mitigation in enhancing infrastructure resilience. The proposed framework thus offers a versatile and validated simulation tool for emergency planners to proactively assess and optimize evacuation strategies under various damage scenarios. Full article

Dams are widely distributed in global water bodies and cause severe impacts on aquatic ecosystems. In this study, the Sizao River Basin was selected to explore the effects of dams on the macroinvertebrate community, including functional feeding groups (FFGs). Macroinvertebrate communities and environmental variables were monitored seasonally in April, August, October, and November of 2025. A total of 27 taxa were identified, including 3 phyla, 8 orders, and 15 families. Species richness, abundance, biomass, species diversity, and FFGs diversity in the gate-regulated section were generally lower than those in other river sections. Gatherer–collector dominated FFGs across the Sizao River Basin and accounted for most of the dominant species. An ecosystem assessment based on FFGs suggests that ecosystem attributes of macroinvertebrate communities were fragmented. The longitudinal spatial distribution of FFGs was roughly in line with the predications of the river continuum concept. Redundancy Analysis (RDA) indicated that the permanganate index (COD_Mn) and dissolved oxygen (DO) were major environmental variables affecting macroinvertebrate community structure, and DO and salinity (SAL) were major variables affecting FFGs. The explanatory power of RDA for FFGs was higher than that for macroinvertebrate community structure. These findings provide valuable insights into protecting aquatic ecosystems in gate-regulated water bodies. Full article

The sustainable management of water supply reservoirs requires analysis of spatiotemporal variations in nutrient levels, phytoplankton composition, and trophic status. The Katse Dam (KD) is a strategic raw water supply source that generates hydropower and sustains aquaculture. However, it is exposed to nutrient enrichment from mining and aquaculture, whose impact on its trophic status necessitates monitoring. This study applies the organic pollution index (OPI), the modified pollution index (MPI), and Carlson’s trophic state index (CTSI) to assess the trophic status of KD. The results from the first decade (FD) (2003–2013), when the intensity of mining and aquaculture activities was minimal, were compared with the results from the second decade (SD) (2014–2024) when there was higher activity. The MPI revealed that KD transitioned from a contaminated status during the FD to a greatly contaminated status during the SD. KD shifted from mesotrophic to eutrophic in the transitional zone and from eutrophic to hypereutrophic in the lacustrine zone. The cyanobacteria Radiocystis sp. replaced Asterionella sp. and became the most abundant algae in the SD, followed by the diatom Flagilaria sp. Principal component analysis (PCA) indicated stronger correlations between NH₄, PO₄, NO₃, and NO₂, while canonical correspondence analysis (CCA) indicated a strong correlation between PO₄ and Fragilaria sp. in the SD. The OPI classified KD water quality as excellent, with the exception of the lacustrine zone, where the water quality was polluted in 2016 and 2021. The data analysis revealed how long-term variations in KD water chemistry and phytoplankton influenced trophic status. This study thus provides water managers with a template for assessing water quality to secure the strategic value of the KD. Full article

Probiotic supplements are increasingly being touted to have health benefits for pregnant women consuming such supplements and their unborn offspring. The placenta is in direct communication with maternal blood, and bioactive agents can thus easily be transferred to this organ where they may influence gene expression by the different trophoblast (TB) cell lineages. The underlying hypothesis assessed herein is that maternal probiotic supplementation can influence the placenta and fetal brain. The composition of bacterial short-chain fatty acids (SCFAs) was examined in fecal boli of mouse dams on a maternal probiotic supplement relative to control dams. Further, SCFA and transcriptomic profiles were examined in placenta and fetal brain from conceptuses derived from dams on the probiotic supplement and conceptuses from control dams. While this treatment did not affect bacterial SCFAs, placenta and fetal brain changes were evident in male and female conceptuses carried by dams receiving probiotics relative to controls. For the placenta, females were more sensitive to maternal probiotic supplementation, whereas the opposite was the case for the fetal brain. Slc6a4 showed increased expression in female placenta from probiotic-treated dams, which could enhance uptake of maternal 5-HT. Male placenta from probiotic-treated dams had dramatic reduction in Hsd11b2 that may render them more vulnerable to maternal stress. In the fetal brain, maternal probiotic supplementation was associated with genes linked to forebrain development, suggesting this treatment might impact life-long neurobehavioral responses. Current studies suggest that maternal probiotic supplementation might lead to adverse changes in the placenta and fetal brain of their unborn children. Full article

Climate change, depleting fossil fuel reserves, and instability in petroleum prices are driving developing economies to explore cost-effective, efficient, and sustainable energy sources such as hydropower. However, there is an ongoing debate regarding the relevance, suitability, and impact of mega-dams. Much of the existing research on mega-dams examines this debate through the lens of development theories. However, mega-dams impact a wide range of stakeholders at local, national, regional, and global levels, necessitating exploration of their role from a socioeconomic perspective. This interdisciplinary case study draws knowledge from management, sociology, and economics and provides a comprehensive account of multi-stakeholder perspectives on the impact of a mega-dam and addresses the research question: How do stakeholders perceive the impact of the Merowe Dam on agricultural livelihoods, and how do they interpret the role of governance processes? Participants included farmers, a focus group with 10 members from the affected communities, and 32 key informant interviews from non-governmental organizations, political actors, academics, businessmen and leaders in the catchment areas of the Merowe Dam, Sudan. The findings suggest that despite some concerns about motivations and processes of mega-dam commissioning, these projects are perceived as beneficial for long-term and sustainable socioeconomic growth and gaining support for renewable energy use in developing economies. The participants reported that modernization of agriculture, following the establishment of the dam, increased crop yields, e.g., wheat production has increased per hectare. Farmers’ income and irrigated land have increased substantially per family due to an increase in land sizes allocated to relocated communities, leading to an overall increase in land size. Therefore, with improved processes in both pre- and post-commissioning stages, transparency, accountability, and deeper stakeholder engagement, mega-dams can facilitate a smoother transition from fossil fuels to large-scale hydropower on one hand and livelihood enhancement through agriculture and other income generating activities on the other. Full article