Search Results (458)

An emerging environmental pollutant, microplastics have garnered global attention due to their widespread presence in soil and aquatic ecosystems. Early research primarily treated microplastics as single pollutants, focusing on their individual toxic effects. However, microplastics in the environment exist as a complex mixture, comprising various polymer types, sizes, shapes, and aging states. This diversity influences how microplastics regulate ecosystem carbon and nitrogen cycles and intervene through pathways such as direct carbon input, physical disturbance, microbial community restructuring, and coupled effects. This paper systematically reviews the characteristics of microplastic diversity and its mechanisms influencing carbon and nitrogen cycles: the chemical structure of polymers determines bioavailability and degradation rate, with biodegradable plastics altering carbon and nitrogen transformations more significantly than conventional plastics; microplastics of different sizes affect nitrogen transformation dynamics by modulating specific surface area and microbial colonization, with small-sized biodegradable microplastics particularly inhibiting plant nitrogen uptake; aging modifies surface properties and dissolved organic carbon release, thereby enhancing their role in promoting greenhouse gas emissions. Existing studies are largely confined to short-term laboratory simulations, leaving a gap in understanding the comprehensive effects of microplastic diversity under long-term, field conditions. Future research should focus on standardized methods and long-term experiments with multi-factor coupling to provide a scientific basis for ecological risk assessment of microplastic pollution. Full article

Sustainable water remediation requires catalytic strategies that remove contaminants efficiently while reducing chemical input, byproduct formation, and ecological disturbance. Conventional radical-dominated advanced oxidation processes can rapidly degrade pollutants, but their reliance on high oxidant dosages and freely diffusing reactive oxygen species often causes matrix quenching, non-selective oxidation, low oxidant utilization, and potential ecological risks. Mild interfacial catalysis provides a materials-chemistry strategy to regulate oxidative intensity and direct contaminant transformation under environmentally relevant conditions. In this review, mild catalysts are defined by pathway-selective, interfacially confined, and environmentally compatible oxidation rather than by low dosage alone. Representative non-radical or low-intensity pathways, including singlet oxygen generation, surface-mediated electron transfer, high-valent metal–oxo species, and direct oxidative transfer processes, are discussed in relation to active-site structure, oxidant utilization, matrix tolerance, and byproduct control. We further summarize how coordination environments, defect chemistry, heteroatom configurations, nanoconfinement, and immobilized interfaces regulate reactive-species formation and interfacial charge transfer. Key material platforms, including single-atom catalysts, heteroatom-doped carbons, defect-engineered oxides, catalytic membranes, hydrogels, and floating or immobilized composites, are evaluated from mechanistic and application-oriented perspectives. Finally, catalyst regeneration, cost, microbial community responses, algae–bacteria balance, ecotoxicity, and long-term safety are discussed to guide sustainable aquatic ecosystem restoration. Full article

Freshwater amphipods of the genus Gammarus are important trophic components of aquatic ecosystems and are increasingly considered a potential bioresource for aquaculture. However, their role in the maintenance and transmission of infectious agents remains poorly understood. This study evaluated the presence of major crustacean and fish pathogens in Gammarus lacustris populations from Kazakhstan and characterized associated viral communities using metagenomic sequencing. Six pooled samples collected from freshwater ecosystems across Kazakhstan were screened using PCR and RT-PCR assays targeting World Organisation for Animal Health (WOAH)-listed pathogens, including White Spot Syndrome Virus, Taura Syndrome Virus, Infectious Myonecrosis Virus, Aphanomyces astaci, and Aphanomyces invadans. In parallel, high-throughput sequencing (Illumina NovaSeq) was performed to assess virome composition and structure. No WOAH-listed pathogens were detected, suggesting a low detectable occurrence of major notifiable agents under the conditions of the present study. Metagenomic analysis revealed a virome dominated by RNA viruses, particularly picorna-like viruses (Picornaviridae), Dicistroviridae, and Marnaviridae. Phylogenetic and genome organization analyses identified potentially novel or highly divergent viral lineages within Picornavirales. Collectively, these findings suggest a favorable epizootiological profile of G. lacustris populations while highlighting freshwater amphipods as hosts of diverse and partially uncharacterized viral communities relevant to aquatic disease surveillance and aquaculture biosecurity. Full article

Plateau waters in Northern Sichuan, China, act as critical headwaters of the Yellow River. Microbial communities in water bodies and soil matrices within this region are increasingly pressured by intensive animal rearing; yet few studies have characterized microbial shifts across entire riverine niches. In this study, we employed next-generation sequencing based metagenomics to investigate microbial features, community structure and diversity, metabolic potentials, and antibiotic resistance genes (ARGs) in the Baihe River, a tributary in the source region of the Yellow River. Sampling locations covered the main stem and three tributaries of the Baihe River, spanning from its source, through upstream and downstream segments, to the convergence site with the main stem of the Yellow River. Results revealed that Pseudomonadota and Bacteroidota were the most abundant phyla. The relative abundance of most taxa at multiple taxonomic levels exhibited an increasing trend along the river continuum driven by rising total nitrogen (TN) and total phosphorus (TP) concentrations; however, a notable exception occurred at BH1 (the Baihe source), where the abundance of numerous taxa was markedly higher than in downstream samples. We detected abundant ARGs predominantly associated with antibiotic resistance. Furthermore, prevalent viruses affiliated with the phyla Uroviricota and Nucleocytoviricota, together with pathogenic bacteria, were identified as etiological agents of diverse infectious diseases. This study provides novel perspectives for managing aquatic contamination in plateau river ecosystems by linking environmental variables, microbial succession, and resistome distribution. Full article

Urban aquatic ecosystems are increasingly shaped by anthropogenic pressures that alter community structure and ecological functioning. This study investigates how the functional organization of zooplankton communities reflects ecosystem stability along an urbanization gradient in the Colentina River–Lake system (Romania). Zooplankton taxa were classified into trophic guilds and size-based functional groups, and functional diversity was quantified using the FEve, FDiv, FDis, and RaoQ indices, based on functional trait structure and distribution within communities. Ecosystem stability patterns were estimated through zooplankton community resilience (RSL) and resistance (RST), indices derived from Shannon diversity and Pielou evenness. Across the system, filter feeders dominated, and their density increased toward downstream, highly urbanized sectors. Also, small-sized organisms (SMC) were consistently prevalent, representing a zooplankton component commonly associated with stress tolerance and opportunism in disturbed aquatic environments. Functional diversity patterns showed low evenness but high divergence, suggesting that although few functional strategies dominate, communities maintain internal differentiation. While filter feeders remained dominant even in disturbed sectors, the uneven distribution of other groups, especially scrapers, may reflect greater sensitivity to anthropogenic conditions. These findings suggest that functional trait composition, in addition to diversity, plays an important role in shaping structural stability patterns. These findings indicate that functional trait composition, in addition to diversity, was associated with the observed stability patterns. The study reinforces the value of zooplankton as sensitive indicators of functional integrity in anthropogenically impacted freshwater systems and provides insights relevant for sustainable urban water management. 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

Tropical wetlands are highly sensitive to climatic and anthropogenic disturbances, and their macrophyte communities provide valuable information about environmental conditions and habitat structure. This study evaluated the relationship between aquatic macrophyte richness, community composition, and habitat vulnerability to climate change in aquatic ecosystems of the San Luis rural district, Barrancabermeja municipality (Santander, Colombia). Macrophyte communities were characterized at 47 monitoring sites distributed across six mesohabitats: floodplain depressions, swamp, wetland, artificial ponds, naturalized ponds, and stream riparian zones. A total of 63 species belonging to 30 families and 51 genera were recorded. Contrary to theoretical expectations, correlation analyses showed no significant relationship between macrophyte species richness and habitat vulnerability indices (Spearman ρ = −0.118, p = 0.428; Pearson r = −0.069, p = 0.646). However, species richness differed significantly among mesohabitats (Kruskal–Wallis, p < 0.05), indicating strong spatial heterogeneity in aquatic plant distribution. In addition, multivariate analyses using Principal Component Analysis (PCA) revealed that macrophyte community composition was strongly structured by local anthropogenic activities, including livestock farming, oil palm cultivation, and wastewater inputs. Floodplain depressions and artificial ponds were dominated by disturbance-tolerant and eutrophication-resistant species such as Urochloa plantaginea and Salvinia minima, reflecting higher levels of environmental pressure. These results demonstrate that macrophyte community composition, rather than species richness alone, is a more reliable indicator of habitat conditions and anthropogenic disturbance in tropical wetland systems. Overall, this study highlights that taxonomic richness is not a robust predictor of climate-related vulnerability in highly disturbed wetlands and emphasizes the importance of considering species composition and environmental context when assessing ecosystem conditions. 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

Aquatic environments that support tourism, including coasts, lakes, reservoirs, and estuaries, are experiencing accelerating eutrophication worldwide. This trend increases the frequency and intensity of algal blooms. These blooms undermine ecosystem services and weaken the socio-economic performance of destination areas. Despite these challenges, existing research remains fragmented. Aquatic sciences mainly examine nutrient enrichment and bloom dynamics. In contrast, tourism studies often treat blooms as episodic disturbances and rarely integrate exposure pathways, risk communication, or feedback to destination governance. This review synthesizes evidence across freshwater and marine systems to develop a coupled tourism–water ecosystem perspective. We link eutrophication drivers and bloom typologies to three dimensions. These are the degradation of tourism-supporting ecosystem services, compound health stressors, and communication filters. The first includes losses of water clarity and aesthetic value. The second involves multi-route exposure through contact, inhalation, and seafood ingestion. The third shapes perceived safety, trust, and behavioral adaptation. We further connect perceived health risks to observable tourist behaviors, including cancellation, destination substitution, and activity avoidance. These micro-level responses can aggregate into market-level demand contractions and consumption reallocation. They can also trigger regional economic cascades, including public management costs, employment impacts, and long-term reputational damage. Crucially, tourism is not merely a victim of blooms. It can also act as a reinforcing anthropogenic driver through wastewater burdens, infrastructure expansion, and pulse pressures. These pressures lower ecological resilience, especially under warming and hydrological stabilization. Finally, we identify governance leverage points. These include early-warning systems, threshold-based graded interventions, transparent risk communication, and integrated social–ecological modeling. These strategies can reduce uncertainty-driven losses and support adaptive destination management. Overall, this review reframes algal blooms as systemic social–ecological risks. It provides a structured basis for future empirical attribution and policy design in tourism-dependent waters under climate stress. Full article

The Amazon coastal zone exhibits remarkable habitat diversity and species richness, with nutrient-rich estuaries playing a crucial role in local food webs and supporting fish and other aquatic organisms. To examine the distribution of fish larvae and juveniles in the Taperaçu Estuary and their relationship with environmental variables, monthly sampling was conducted at two fixed stations in 2008. Samples were collected during flood and ebb spring tides using 500 μm mesh nets. In situ measurements of salinity, temperature, and dissolved oxygen were recorded, while pH and turbidity were determined in the laboratory. Abiotic variables did not differ significantly between tides, but salinity and dissolved oxygen were higher during the dry season. A total of 5175 individuals were identified, representing 17 families and 37 species. The ichthyoplankton community was dominated by Rhinosardinia amazonica, Anchovia clupeoides, Stellifer stellifer, and Microgobius meeki. Stations 1 and 2 showed differing abundance ranges, with higher values at station 1 during the rainy season. Preflexion stages were abundant at both stations, indicating the estuary’s importance as a nursery and development area for several fish species. Multivariate analyses revealed spatial and seasonal structuring of larval assemblages along the estuarine gradient, driven primarily by salinity, temperature, and turbidity. Our results emphasize the role of upper estuary sectors of eastern Amazonia as areas of spawning, larval development, and subsequent juvenile settlement, contributing to the dispersal of fish species throughout the estuary and adjacent coastal environments. The present findings also reinforce the ecological value of the studied Extractive Reserve and other protected areas along the Amazon littoral as essential habitats for larval refuge and development. The need for continued monitoring and preservation of these protected zones is evident. Full article

The gut microbiota of fish plays a crucial role in nutrition, metabolism and immune regulation, and is highly sensitive to environmental stressors such as pesticide exposure. This study investigated the effects of emamectin benzoate (EMB) exposure on Asian stinging catfish (Heteropneustes fossilis) gut microbiota using an integrated culture-dependent and culture-independent approach to assess functional and taxonomic dysbiosis. Gut smear samples from control and EMB-treated fish at two sublethal concentrations (0.5 µg/L and 5 µg/L) were analyzed for major functional bacterial groups, including heterotrophic, lipid-hydrolysing, starch-hydrolysing, spore-forming, and Gram-negative bacteria and Pseudomonas spp., using standard plate count techniques. In parallel, microbial community composition and diversity were examined through 16S rRNA (V3–V4 region) gene amplicon sequencing followed by bioinformatic analysis. Culture-based results showed a significant decline in total heterotrophic bacteria and key functional groups in EMB-treated fish, indicating suppression of microbial metabolic activity and functional imbalance. Lipid-hydrolysing and starch-hydrolysing bacteria showed pronounced sensitivity to pesticide exposure, while spore-forming bacteria exhibited a marked reduction, suggesting compromised microbial resilience. Although Gram-negative bacteria declined overall, Pseudomonas spp. displayed a non-linear response, with an initial decrease, followed by partial recovery under higher exposure. Culture-independent analysis demonstrated reduced alpha diversity, altered community structure, and taxonomic shifts in EMB-treated fish. Pseudomonadota exhibited a distinct pattern characterized by decline at 0.5 µg/L and partial recovery at 5 µg/L, reflecting adaptive tolerance rather than restoration of microbial homeostasis. Overall, the combined evidence indicates pronounced EMB-induced gut dysbiosis at both functional and compositional levels. This study highlights the fish gut microbiome as a sensitive biomarker of stress and underscores the ecological risks associated with EMB in aquatic environments. Full article

Rapid and accurate diagnosis of infectious diseases in aquaculture is essential for preventing major economic and ecological losses. Traditional culture-based methods focus on isolation of individual pathogens, and often are burdened with extended processing times, particularly during investigations of polymicrobial infections. Application of Oxford Nanopore Technologies (ONT) sequencing offers a rapid, culture-independent workflow for the identification of bacterial and fungal pathogens directly from fish tissues. Swab and organ samples from four cases (1: Salmo spp.; 2: Cyprinus carpio; 3: Salvelinus fontinalis; 4: Heniochus acuminatus) were analyzed using ONT long-read sequencing for metagenomic screening and bioinformatic classification. The results revealed case-, species-, and tissue-specific microbial profiles, with external tissues showing higher microbial diversity and internal organs enriched in pathogenic taxa. Dominant pathogens included Streptococcus iniae, Aeromonas hydrophila, Pseudomonas spp., and Saprolegnia parasitica, alongside opportunistic zoonotic bacteria such as Escherichia coli and Acinetobacter baumannii. We demonstrate the potential for diagnostic application of ONT sequencing in investigations and detection of multi-pathogen infections, including assessments of microbial community structure changes during disease outbreaks in aquatic species. The presented workflow enables rapid, cost-effective, and comprehensive pathogen profiling, supporting early disease surveillance and improved management in aquatic veterinary practice. Full article

All-trans retinoic acid (atRA) is known to regulate lipid metabolism, adipocyte differentiation, and the immune system in mammals and other aquatic species. However, studies on atRA in crustaceans, especially in Eriocheir sinensis, are still scarce. The present study aimed to investigate the regulatory effects of dietary or injected atRA on female crabs during the fattening period. In the dietary regulation experiment, 270 female crabs were fed diets containing different doses of atRA (0, 150, 300, 600, 1200, and 2400 mg/kg) for a total of 49 days. In the in vivo injection experiment, 90 females were divided into an experimental group (injected with a 0.3 μg/g dose of atRA) and a control group (injected with the same amount of DMSO solvent). Injections were given weekly throughout the 35-day experimental period. Results: Both dietary atRA and atRA injection promoted ovarian development, as evidenced by increased GSI, elevated serum Vg levels, decreased GIH, and upregulated expression of vg, vgr, and rxr genes. In terms of mechanism, dietary atRA promoted ovarian development via the upregulation of pyrimidine nucleotides and dehydroepiandrosterone, which supplied nucleic acid precursors and hormonal support. Furthermore, RXR was identified as a potential key target of atRA in inducing ovarian development, as molecular docking revealed that atRA could spontaneously bind to RXR. Moreover, following atRA injection, the expression of rxr, along with key genes involved in ovarian development, lipid synthesis, and lipid transport, was significantly upregulated. In addition, the atRA diet created a favorable microenvironment for ovarian development by reducing pro-inflammatory lipid levels in the ovary. Transcriptomic and metabolomic analyses revealed that atRA modulates energy and lipid metabolism by activating the AMPK pathway. In terms of the bacterial community structure, the atRA diet significantly decreased Fusobacterium abundance and enriched Parabacteroides as the signature beneficial bacterium. In terms of nutritional quality, the atRA diet markedly reduced saturated and trans-fatty acids while increasing monounsaturated fatty acids and various key essential amino acids. Conclusions: This study revealed that atRA plays a key role in promoting ovarian development, improving nutritional quality, and modulating the structure of the microbiota, thereby providing theoretical support for healthy aquaculture of female crabs during the fattening period. 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

Water hyacinth (Pontederia crassipes Mart.) is native to the Amazon basin. It has spread to freshwater ecosystems in over 80 countries in tropical, subtropical, and warm temperate regions. Due to its invasive nature, water hyacinth is listed among the world’s 100 worst invasive alien species. Infestations of water hyacinth affect the abiotic components of these ecosystems, including water evaporation, flow, and quality; oxygen and nitrogen levels; sunlight transmission; and greenhouse gases. These changes reduce the abundance and diversity of primary producers in the food web, including phytoplankton and aquatic plants. Consequently, these alterations affect consumers in the food web, including zooplankton, invertebrates, fish, and birds. A negative correlation has often been observed between water hyacinth infestations and the abundance and diversity of these organisms, particularly native species. However, the abundance of some introduced species among these consumers has increased due to water hyacinth infestations. These changes alter the structure and function of natural ecosystems compared to what they were before infestations occurred. Infestations also negatively impact daily human activities and livelihoods, harming local communities and increasing disease transmission. Global warming and the eutrophication of freshwater ecosystems allow water hyacinth to spread into additional non-native areas in high latitudes, thereby increasing the threat it poses. Water hyacinth also contributes to global warming by increasing methane emissions. Over the past century, management strategies have shifted toward restoring the structure and function of ecosystems by progressively integrating various sectors. The infestation of water hyacinth is a complicated, site-specific process influenced by time, climate, existing biotic and abiotic factors, and ecosystem resilience. Therefore, long-term monitoring of environmental outcomes is essential for developing sustainable, site-specific strategies. Robust evaluation systems are necessary to track the efficacy of interventions and to understand the broader ecological ramifications of management strategies. Water hyacinth is still sold in some local markets for ornamental purposes. Raising public awareness of its invasive characteristics is necessary. Full article