Search Results (286)

Alpine streams are increasingly exposed to multiple disturbances, including extreme flood events, expected to become more frequent under climate change, and the expansion of small hydropower plants (SHPs). Understanding the resilience of aquatic communities and the ability of biomonitoring tools to detect disturbance-driven changes is essential for ecological assessment. We conducted an eleven-year monitoring programme (2014–2024) in the Corsaglia Stream (Northwestern Italy), comprising 16 sampling campaigns before, during, and after two flood events and SHP construction. Macroinvertebrate and fish communities were analysed using taxonomic, functional, and temporal beta-diversity metrics. Macroinvertebrates were assessed using the nationally standardised STAR_ICMi biomonitoring index and the recently developed Flow-T index. Macroinvertebrate assemblages showed high resilience, recovering taxonomic richness while maintaining “Good ecological status” despite severe flood-induced collapse. Recovery followed a nestedness-to-turnover trajectory, indicating recolonization from refugia rather than community replacement. Flow-T detected transient functional changes not captured by STAR_ICMi. In contrast, fish communities exhibited persistent structural changes, with reduced abundance, marked shifts in species composition, and slower recovery of native salmonids and European bullhead (Cottus gobio) under combined flood and hydropower impacts. These findings show that integrating taxonomic, functional, and temporal approaches improves ecological assessment beyond single-index biomonitoring approaches such as STAR_ICMi alone. Full article

As critical biological components of freshwater ecosystems, aquatic insects are highly sensitive to cumulative anthropogenic disturbances and can effectively reflect long-term variations in river ecological quality, serving as ideal bioindicators for aquatic ecological monitoring and assessment. However, most existing benthic biotic integrity indices integrate diverse macroinvertebrate groups, which dilute the unique indicative value of aquatic insect communities, and few targeted evaluation systems have been independently developed for highly disturbed plain river basins in northern China. In this study, a field investigation of aquatic insect communities was conducted across 32 sampling sites in the Haihe River Basin from April to September 2023, aiming to construct a novel Aquatic Insect-based Index of Biotic Integrity (Ai-IBI) and systematically evaluate the basin’s river ecosystem health status. A total of 10,267 aquatic insect individuals belonging to eight orders and 43 families were identified, with Chironomidae dominating the community and predominantly distributing in midstream and downstream reaches. Based on ecological principles, discriminant ability analysis, and redundancy analysis, four core metrics were ultimately screened out to establish the Ai-IBI system, including total taxa richness, percentage of the top three dominant taxa, density of tolerant groups, and percentage of predators. Considering the widespread background ecological degradation of the Haihe River Basin, a localized reference-site selection framework integrating water quality standards, physical habitat assessment, and field ecological surveys was adopted to determine eight minimally disturbed reference sites, which effectively improved the regional applicability of the evaluation model. The health assessment results indicated that only a small proportion of river reaches maintained a healthy state, while most sites were classified as sub-healthy or fair, presenting a distinct spatial differentiation pattern wherein upstream mountainous reaches exhibited superior ecological integrity compared with downstream plain reaches. The constructed Ai-IBI showed high consistency with conventional physicochemical indicators and habitat evaluation results, verifying its excellent reliability and robustness. Different from traditional empirical IBI models suitable for near-natural watersheds, the Ai-IBI fully adapts to the unique ecological background of long-term water resource overexploitation, urbanization-induced habitat fragmentation, and nutrient enrichment in the Haihe River Basin. The Ai-IBI developed in this study provides a refined biological evaluation tool for quantitative diagnosis of river ecological degradation, offers empirical support for differentiated ecological protection and precise restoration strategies in the Haihe River Basin, and serves as a feasible methodological reference for ecological health assessment in other human-dominated plain river basins globally. Full article

Mideopsis roztoczensis Biesiadka & Kowalik, 1979 (Acari, Hydrachnidia, Mideopsidae) is a common and often abundant component of macroinvertebrate communities in Palearctic streams. Although the external morphology and genetic structure of this species are relatively well documented, knowledge of its internal anatomy remains limited, despite its importance for an integrative understanding of morphology and evolutionary diversity. The present study utilized histological techniques to investigate and describe the internal structures of M. roztoczensis based on newly collected material from Serbia. Histological analyses revealed the organization of several internal organs, including an extensive blind sac-like excretory organ that was morphologically distinct from the midgut, while a hindgut was not identified. Additionally, other structures, including dermal glands, the midgut, salivary glands, and the synganglion, were characterized. The observed variation in internal organization, particularly the morphology of the excretory organ and the number of paired dermal glands, provides additional characteristics in comparative morphological studies of water mite. This study contributes to our current knowledge of the internal anatomy of Hydrachnidia and highlights the value of histological approaches for future integrative studies of water mites. Full article

National biomonitoring programs increasingly survey multiple biological assemblages, but whether one biological element can serve as a surrogate for the magnitude or ranking of repeated-survey compositional displacement remains unresolved under strict site-year-round matching. We analyzed Korean National Aquatic Ecological Monitoring Program records from 2011 to 2023 using a strict core of 13,386 site-years from 3016 matched lotic sites in which epilithic diatoms, benthic macroinvertebrates, and fish were recorded in both monitoring rounds. For each assemblage separately, we calculated standard Hellinger dissimilarity between Round 1 and Round 2 relative-abundance vectors. Spearman rank concordance was −0.012 (−0.030 to 0.005) for diatom–macroinvertebrate, 0.034 (0.015 to 0.052) for diatom–fish, and −0.014 (−0.034 to 0.005) for macroinvertebrate–fish; corresponding Pearson correlations ranged from −0.010 to 0.041. Within-site-centered associations, correlations among site-level mean dissimilarities, broader pairwise matched datasets, and alternative relative-Euclidean and Bray–Curtis metrics all remained weak. Thus, under the present monitoring design, the magnitude or ranking of between-round compositional displacement in one assemblage provided little information about the corresponding displacement in another. The three assemblages were surveyed by separate specialist teams within the same nationally prescribed round-specific seasonal windows rather than by required same-day co-sampling. The result is therefore interpreted at the operational survey-round scale; temporally linked environmental covariates and the replicate information needed to quantify observation error were not analyzed. Full article

Urban freshwater ecosystems are exposed to multiple anthropogenic pressures, but their effects on macroinvertebrate communities may vary depending on waterbody type and surrounding land use structure. This study analysed macroinvertebrate communities in three waterbody types of the Belgrade functional urban area. Land use was classified into agricultural, artificial, and semi-natural areas, and evaluated using LUI and HHI indices. A total of 187 macroinvertebrate taxa were recorded, indicating high diversity despite the urban setting. Community composition differed among waterbody types, with non-wadeable rivers characterised by a high proportion of Oligochaeta, wadeable rivers by a greater contribution of insects, and canals by the dominance of crustaceans. Land use further influenced community structure: semi-natural areas were associated with a higher proportion of crustaceans, artificial areas with Chironomidae, and agricultural areas with Oligochaeta. Alpha diversity was highest in wadeable rivers, while beta diversity showed that compositional differences were driven by species turnover. SPEAR indices indicated stress-related differences among waterbody types. CCA showed that community variation was associated with conductivity, temperature, oxygen saturation, pH, BOD, TOC, AOX, and phosphate. Overall, macroinvertebrate communities in the Belgrade urban area are shaped by the combined effects of waterbody type, land use structure, and local environmental conditions. Full article

Rice paddies function as temporary wetlands that provide important habitats for diverse aquatic macroinvertebrates. However, the relative roles of regional climatic conditions and invasive species in shaping macroinvertebrate communities remain insufficiently understood. This study investigated the effects of regional temperature variation and the invasive apple snail Pomacea canaliculata on aquatic macroinvertebrate communities in rice paddies across South Korea. Aquatic macroinvertebrates were surveyed annually from 2021 to 2024 in five regions distributed along a latitudinal gradient, and additional local-scale comparisons were conducted between rice paddies with and without P. canaliculata. A total of 42 species comprising 24,524 individuals were recorded. Community composition differed significantly among regions and variation partitioning indicated that regional temperature explained 17.5% of the community variation in paddies containing P. canaliculata, whereas the snail explained 2.3%. Several dominant aquatic insect species exhibited distinct temperature-associated distribution patterns, with Rhantus suturalis and Hydrochara affinis showing negative relationships with temperature and Sternolophus rufipes showing a positive relationship. In contrast, P. canaliculata had little influence on aquatic insects but reduced overall macroinvertebrate diversity through its negative effects on native gastropod assemblages. These findings demonstrate that regional temperature and P. canaliculata influence rice-paddy macroinvertebrate communities through different ecological pathways. Regional temperature primarily affects the distribution of several dominant aquatic insect species, whereas P. canaliculata alters community diversity by reducing native gastropod populations. This study provides ecological evidence for predicting the combined impacts of climate warming and biological invasion on rice-paddy ecosystems. Full article

This study provides a preliminary baseline characterization of macroinvertebrate assemblages colonizing floating islands installed in two NE Portuguese river reaches with contrasting anthropogenic and hydromorphological conditions: the urban, weir-influenced Fervença River and the more rural, reservoir-like Côa reach within a former dam-work area. A single campaign in February 2025 combined water characterization and macroinvertebrate sampling on islands and adjacent margins. Fervença showed higher mineralization and microbiological contamination, but a more varied assemblage dominated by tolerant taxa. Côa showed better water quality but strong Astacidae dominance. Results indicate colonization only; robust replicated monitoring is needed before inferring ecological improvement. Full article

Riverine mercury biomagnification is most frequently studied via metrics such as the trophic magnification factor (TMF), the biomagnification factor (BMF) and the trophic magnification slope (TMS). However, these metrics prove problematic in lotic systems dominated by benthic macroinvertebrates because short food chains, the frequent lack of fish, patchy basal production and marked spatial heterogeneity obscure the signal that they are meant to extract. We argue that stable isotopes of carbon and nitrogen (δ¹³C, δ¹⁵N) are not merely optional enhancements but are a prerequisite for a mechanistic understanding of the transfer of methylmercury (MeHg). Nitrogen isotopes distinguish among trophic positions not as categories, but as gradients, whilst carbon isotopes reflect the underlying pathways increasingly seen as defining how MeHg enters food webs. Invertebrate studies, published more recently, report systematically lower magnification levels compared to community-based studies and become far more comprehensible when carbon source and trophic pathways are made explicit, with Hg isotopes (δ²⁰²Hg, Δ¹⁹⁹Hg) providing supplementary data about mercury sources and processing. To be able to carry out reliable river monitoring, such frameworks require clarity in choices of background value, discrimination factors and statistical methods. Full article

Climate change models point to a possible rise in air temperature, ranging from 2 °C to 4 °C. Global changes will therefore have a particularly pronounced effect on the functioning of shallow water bodies known as peat ponds, i.e., habitats formed after peat extraction in peatlands. However, the extent of this impact is still unknown. The main objective of the study was to determine the impact of water level and water physicochemical properties on the functioning of selected groups of aquatic organisms in peat ponds of different origins. The study was conducted in spring, summer and autumn of the years 2024 and 2025, in 10 peat ponds with different trophic status and typology, located in the Polesie National Park in eastern Poland. Considerable fluctuations in water levels, resulting from a scarcity of precipitation, accelerated the drying out and overgrowth of peat ponds, particularly the alkaline and acidic types. Within the zoocoenotic communities, a significant decline in the abundance of planktonic species and an increase in the abundance of littoral or periphytic species were recorded (F = 6.24, p < 0.015). Regarding trophic structure, an increase in the abundance of mixotrophic species and a decrease in the abundance of top-level predators were observed. Hydrological changes were reflected in an increase in species richness and abundance of communities of organisms with broad ecological tolerance (mainly ciliates), and a decrease in the number of species and abundance of planktonic crustaceans and macroinvertebrates. The RDA model explains over 84% of the total variability, indicating excellent model fit to the data and a strong correlation between environmental variables and species composition. Based on p values, water level, temperature, pH, and COD were selected as significant variables, with conductivity, O₂, and P_tot demonstrating less statistical significance. Peat ponds ecosystems can serve as an excellent model system for studying the impact of intensifying climate change on the functioning of shallow water bodies. Full article

As an artificial–natural composite ecosystem, polders face increasingly prominent internal and surrounding water environment problems under sustained strong human activities. To systematically assess the water ecological health status of polders around Dongting Lake, this study took four typical polders around Dongting Lake as research subjects, and two seasonal surveys of benthic macroinvertebrates were carried out in July and December 2024. Through analyses of community structure characteristics and correlations with key environmental factors, the Trophic Level Index (TLI), Water Quality index (WQI), Shannon–Wiener index of benthic macroinvertebrates, and Benthic Macroinvertebrates Index of biotic integrity (B-IBI) were selected to establish an entropy-weighted Bayesian model for comprehensive evaluation of the current ecological health of Dongting Lake polders. In 2024, a total of 47 benthic macroinvertebrate species were found in Dongting Lake polders, including 25 species in the summer and 36 species in the winter. The main groups were Gastropoda, Insecta, and Bivalvia, and the community composition did not show significant seasonal or spatial differences. The benthic macroinvertebrate community structure in the summer was mainly influenced by TN/TP, NO₃⁻-N, WD, Tur, and Chl.a, suggesting eutrophication as a critical concern, while in the winter it was mainly regulated by WSW, WT, Tur, and DO, highlighting hydrological conditions as pivotal. The entropy-weighted Bayesian assessment indicated an overall aquatic ecological health status of “moderate” in 2024, with summer conditions superior to those in the winter and notable spatial heterogeneity observed in winter sampling sites within ditches, among which Polder Chengxi exhibited the best condition, while Polder Junshan and Polder Xiangbin Nanhu showed degraded states. Notably, Polder Junshan (JS2 and JS3) displayed clear signs of ecological degradation during the winter, warranting immediate initiation of targeted restoration measures. This study provides a systematic diagnosis and scientifically grounded evaluation of aquatic ecological health in Dongting Lake polders, offering a robust theoretical framework and empirical data for future water environmental protection strategies and ecological restoration practices. Full article

High-mountain lotic ecosystems in the tropical Andes are increasingly threatened by agricultural expansion and seasonal hydrological variability. This study evaluates structural water quality shifts and benthic macroinvertebrate community assembly across an environmental degradation gradient in the La Chorrera micro-basin (Boyacá, Colombia). A weighted multiplicative Water Quality Index (mWQI), originally developed in previous literature, was implemented and validated alongside biotic scores (BMWP/Col) and Canonical Correspondence Analysis (CCA) across 16 sampling points during contrasting wet and dry seasons. The results demonstrate that intense precipitation during the wet season introduces a volumetric dilution effect, maintaining high ecological quality scores (mWQI > 80.0) even in deeply modified agricultural sectors. Conversely, severe baseflow contraction during the dry season triggers pollutant concentration, driving total phosphorus to hyper-eutrophic peaks (9.20 mg/L) and forcing a complete mathematical collapse of the index (mWQI = 0.00). The CCA biplot confirmed that seasonal chemical filters combined with hypoxia (<60% oxygen saturation) eliminate highly responsive macroinvertebrate orders (Ephemeroptera, Plecoptera, Trichoptera), leading to absolute dominance of hypoxia-tolerant opportunists (Chironomidae and Oligochaeta). The benthic community shifted from physical stress (sedimentation) during the wet season to chemical stress (nutrient toxicity and oxygen depletion) during the dry season. The multiplicative framework effectively isolates localized ecological tipping points, providing a high-sensitivity baseline tool for targeted watershed restoration in tropical alpine regions. Full article

Brachymystax lenok tsinlingensis is an endangered salmonid endemic to China. Traditional trapping methods frequently fail to detect this rare fish in low-density mountain streams, hampering evidence-based conservation. Here, we employed environmental DNA quantitative PCR (eDNA-qPCR) with species-specific primers to assess the spatial biomass distribution of this species in the Zhouzhi Heihe River. Concurrently, we surveyed plankton, benthic macroinvertebrates, and physicochemical water parameters. eDNA detected the target species at 12 of 14 sites, with reliable quantification achieved at 9 sites, suggesting that the method may be more effective than conventional trapping for detecting this species under the studied low-density conditions. eDNA-derived relative biomass exhibited pronounced spatial heterogeneity, ranging from 6.0 × 10⁻⁴ to 1.5 × 10⁻² g/cm³. Water depth showed a significant positive association with biomass (r = 0.5347), whereas phytoplankton Shannon diversity (a measure of species richness and evenness) was significantly negatively correlated (r = −0.5447). Flow velocity displayed a negative trend that did not reach statistical significance (r = −0.5009). Plankton and benthic communities indicated overall ecological conditions but did not directly explain the observed spatial variation in fish biomass. These findings indicate that the spatial pattern of B. lenok tsinlingensis is primarily shaped by local physical habitat structure, with deeper, hydraulically more complex channel units serving as key microhabitats. eDNA-qPCR thus represents an effective, low-disturbance monitoring tool for this endangered cold-water fish and provides a scientific basis for targeted habitat protection and restoration. Full article

Introduction: Biological invasions constitute one of the main threats to freshwater ecosystems, causing significant ecological changes through the introduction of exotic species that compete with or prey upon native species. In Portugal, the introduction and spread of exotic species in lotic and lentic ecosystems, such as pike (Esox lucius), European catfish (Silurus glanis), and largemouth bass (Micropterus salmoides), all top predators, may have a big impact on autochthonous species. In contrast, bleak (Alburnus alburnus), European perch (Perca fluviatilis), and common carp (Cyprinus carpio) compete aggressively for food resources. In the Sousa River basin, gudgeon (Gobio lozanoi) is considered an exotic species with potential ecological impact, with the minnow (Phoxinus phoxinus) stand having been recently identified in Portugal and, so far, recorded only in this river basin, and not yet being classified as an invasive species in Portugal. Public knowledge regarding invasive aquatic biodiversity remains a significant bottleneck for conservation. Because recreational angling is a prominent dispersal vector, initiatives that directly target this community are relevant. Objective: The aim is to carry out a bibliographic review on the exotic ichthyofauna species present in the Sousa River, with special focus on the invasion potential of the minnow (P. phoxinus). Methodology: The literature review was conducted based on the ScienceDirect, Springer Nature Link, and Fauna Norvegica databases, selecting publications between 2006 and 2025 concerning relevant studies on the potentially invasive characteristics of the minnow (P. phoxinus). The methodology is based on the analysis of studies regarding the impacts caused on riparian ecosystems. Results: The species P. phoxinus presents a generalist diet and high adaptive capacity, allowing it to colonise new habitats and compete aggressively with native species for trophic resources. Its presence is associated with negative impacts on brown trout populations (Salmo trutta), reducing growth and productivity, especially in mountain ecosystems. Increased species density also causes a significant decrease in benthic macroinvertebrate biodiversity. Studies conducted in the Douro basin indicate that the arrival of minnow in Portugal resulted from human action, probably associated with its use as live bait in recreational fishing. Conservation programmes use diverse tactics to bridge the awareness gap. Recent initiatives feature electrofishing demonstrations to visually differentiate species, theatrical performances, and even culinary show-cooking events using invasive predators like the European catfish to promote harvesting. Conclusions: The potential transition of P. phoxinus into an exotic and invasive species may be associated with the ecological pressure exerted on native communities, particularly through competition for trophic resources, highlighting the need to assess its dispersion in the Sousa basin and its impacts on fish fauna and benthic macroinvertebrates. It is important to do more sampling to understand its real distribution in the Sousa Basin. Additionally is important to explain to recreational anglers and the general population the impacts of fish transfer and the adverse effects of invasive species on freshwater Portuguese ecosystems. Full article

Shallow eutrophic lakes recover from nutrient loading on time scales ranging from less than one year to many decades, yet whether this range is set by the lake or by the biological response group has rarely been quantified within a single monitoring framework. We assembled a five-year (2020–2025) quarterly monitoring panel from three shallow Yangtze-floodplain lakes (Lake Changhu, Lake Liangzihu, and Lake Honghu; 15 stations, 21 quarters) and applied a panel mixed-effect distributed lag model (PME-DLM) to estimate the lag-response windows of phytoplankton and benthic macroinvertebrate densities against five water-quality drivers. Cross-lake consistency was tested with a station-resampled bootstrap, and the contributions of water quality, season, and lake identity to community variation were resolved by three-table variation partitioning. The PME-DLM resolved a 3-month temperature window for phytoplankton and 9–15 month chlorophyll a and temperature windows for benthic communities, while total nitrogen and total phosphorus were non-significant in either group. Cross-lake bootstrap intervals on window width overlapped substantially across the three lakes, whereas cross-group differences in window centre and shape were an order of magnitude greater. Variation partitioning further showed a mirror-image structure in which phytoplankton variation was dominated by the pure water-quality fraction (12.2%) and benthic variation by the water-quality × season joint fraction (5.8%). Within the resolution of this five-year, three-lake panel, group-level differences in lag-response time scale were more apparent than lake-level differences and provide a quantitative basis for matching restoration assessment cadence to pelagic versus benthic recovery. Full article

Mountain stream ecosystems are often considered among the least disturbed freshwater environments; however, increasing land-use pressures may affect their ecological integrity even under apparently high-water quality conditions. This study aimed to assess the relative influence of landscape, physicochemical, and hydromorphological factors on benthic macroinvertebrate communities in three sub-catchments (Ambroz, Jerte, and Tiétar) of the Sierra de Gredos (Central Spain). A total of 33 sampling sites were surveyed, and macroinvertebrate assemblages were analyzed in relation to environmental variables using partial Redundancy Analysis (pRDA) and variance partitioning. All sites were classified as having “Excellent” ecological status based on the Iberian Biological Monitoring Working Party (IBMWP) index. However, multivariate analyses revealed clear spatial patterns and responses to environmental gradients. Results indicated that catchment-scale landscape characteristics defined the pool of potential colonizers, while local physicochemical and hydromorphological conditions acted as secondary filters structuring macroinvertebrate assemblages. Landscape variables explained the largest fraction of variance in community structure (30.6%), followed by physicochemical parameters (29.0%) and hydromorphological indices (24.9%), with a significant shared component (16.5%) indicating interactions among drivers. Agricultural land use, particularly in the Jerte sub-catchment, was associated with shifts in community composition, favoring tolerant taxa such as Diptera, while sub-catchments dominated by natural vegetation supported higher richness of sensitive groups, including Ephemeroptera and Plecoptera. These findings highlight the importance of multi-scale processes in structuring mountain stream communities and reveal limitations of traditional biotic indices in detecting early ecological changes. The results support the integration of catchment-scale variables into ecological assessment frameworks and emphasize the need for preventive, basin-scale management strategies to maintain ecological integrity under increasing anthropogenic pressure. Full article