Search Results (208)

River restoration is increasingly promoted as a nature-based solution, but evidence of its ecological effectiveness in mountain gravel-bed rivers remains limited. Macroinvertebrate responses to hydromorphological restoration are variable and are still rarely evaluated using an integrated approach combining taxonomic, biotic index, and trait-based components. This study examined whether the hydromorphological restoration of the upper Raba River was associated with measurable environmental and ecological differences between the restored and unrestored sections. Six river sections were analyzed, including three restored and three unrestored sections. The environmental characterisation included hydromorphological and physicochemical variables. Benthic macroinvertebrates were sampled in shallow marginal and main-current habitats, and the analyses included assemblage metrics, biotic indices, taxonomic composition, indicator taxa, and functional traits. The restored sections showed greater channel complexity, including a larger active channel zone, a larger number of active channels, and a coarser substrate. These differences were accompanied by higher Shannon diversity, higher values of the Polish Biological Monitoring Working Party index (BMWP-PL), a higher percentage of individuals of Ephemeroptera, Plecoptera and Trichoptera (%EPT), distinct assemblage composition, and shifts in indicator taxa and selected functional traits. The results highlight the value of multidimensional assessment frameworks to evaluate the effects of restoration on mountain rivers. 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

The Biological Monitoring Working Party (BMWP) and Average Score Per Taxon (ASPT) indices, which rely on family-level environmental sensitivity values (FESVs), are widely used in freshwater bioassessment. However, regional differences in taxonomic composition often render existing FESV systems incomplete or incompatible, and the influence of rare families remains poorly understood. Using a historical dataset from the temperate Taizi River basin in Northeast China, we developed a regional FESV system for benthic macroinvertebrates. A total of 67 FESVs were established, including 10 families not previously scored in the UK system. These values followed a normal distribution and were ecologically validated using canonical correspondence analysis (CCA). Both BMWP and ASPT indices showed significant correlations with water quality parameters, the Water Quality Index (WQI), and the Habitat Quality Index (HQI). Notably, excluding rare families (occurrence frequency < 1%) did not reduce but slightly enhanced the responsiveness of both indices. CCA identified HQI, conductivity, and ammonia nitrogen as the primary drivers of community composition, and the inferred ecological preferences aligned well with the assigned FESVs. This study provides a robust, regionally adapted framework for family-level bioassessment in temperate East Asian rivers and supports the exclusion of rare taxa to improve cost-effectiveness and index sensitivity. Full article

Understanding the trophic ecology of fish in mountain lakes is essential for interpreting their functional roles and managing these ecosystems. This study investigated the diet, population structure, and prey selectivity of lake charr (Salvelinus umbla) in three glacial basins of the Eastern Italian Alps: Fusine Superiore, Fusine Inferiore, and Raibl Lakes. In summer 2024, 106 fish were sampled using multi-mesh gillnets, alongside Surber sampling of littoral macrobenthos. Biometric analysis revealed populations dominated by larger size classes (>18 cm), with significant sexual dimorphism, as females were longer and heavier than males. Dietary analysis showed strong reliance on littoral Hexapoda (~90% of prey). High Schoener’s overlap index values (α > 0.90) indicated no clear ontogenetic dietary shifts in the sampled size classes, suggesting that the productive littoral zone provides a stable resource. Ivlev’s electivity index revealed lake-specific prey selection patterns, with Hexapoda positively selected in Lake Fusine Inferiore, Bivalvia and Malacostraca positively selected in Lake Raibl, and weak or absent selectivity in Lake Fusine Superiore. S. umbla appears to be a broad opportunistic feeder with site-specific prey selectivity shaped by local resource structure. Given its debated native status, these findings provide an ecological baseline for assessing its potential effects on benthic communities. Full article

To scientifically evaluate the health of river aquatic ecosystems in the Qianxinan Buyi and Miao Autonomous Prefecture, southwestern Guizhou, systematic surveys of benthic macroinvertebrate and periphytic algal communities were conducted in representative rivers during October 2024 (autumn) and April 2025 (spring), coupled with concurrent water quality monitoring. Reference sites were selected based on water quality indicators and habitat conditions. Core parameters were identified through correlation analysis, discriminatory ability analysis, and distribution range analysis to construct a Benthic Index of Biotic Integrity (B-IBI) and a Periphytic Algae Index of Biotic Integrity (P-IBI) suitable for the region. These indices were then applied to assess the ecological health of the rivers. Additionally, stepwise regression analysis was employed to investigate the key environmental drivers influencing the two biotic integrity indices. The results indicated that: (1) In terms of species composition, the benthic macroinvertebrate community structure was relatively simple, dominated by arthropods, particularly chironomid larvae. Bacillariophyta and Cyanophyta consistently dominated the periphytic algae community. (2) Assessments using both B-IBI and P-IBI showed that the overall river health in spring was slightly better than in autumn. However, more than half of the sampling sites were rated as “fair” or worse in both seasons. The reference sites (S2, S10) consistently exhibited “excellent” or “good” health, while the impaired sites showed significant spatial heterogeneity. Discrepancies between B-IBI and P-IBI ratings at some sites revealed differential responses of the two biological communities to environmental stressors. (3) Stepwise regression analysis unveiled a seasonal shift in key environmental drivers. The primary factor affecting the B-IBI in autumn was biochemical oxygen demand (BOD₅), which shifted to total phosphorus (TP) and ammonia nitrogen (NH₄⁺-N) in spring. For the P-IBI, the main factor changed from dissolved oxygen (DO) in autumn to chemical oxygen demand (COD) in spring. These findings confirm the applicability of the B-IBI and P-IBI systems in this region, and indicate that multi-assemblage integrated assessments can contribute to understanding the health status of river ecosystems in the Qianxinan Prefecture. This study could serve as a scientific reference for the protection, management, and restoration of local river ecosystems. Full article

The Western Amazon is a global biodiversity hotspot, yet the Upper Napo River Basin (UNRB) remains understudied regarding aquatic ecosystem health along anthropogenic gradients. We integrated benthic macroinvertebrate assemblages with physicochemical and microbiological indicators across 45 sites to assess ecological quality under four impact scenarios: Few Threats (FT, reference sites; n = 6), Crop/Aquaculture (CA; n = 22), Gold Mining (GM; n = 10), and Wastewater Discharge (WD; n = 7). Analysis of 2285 individuals (62 families) revealed clear degradation across the anthropogenic gradient. Reference sites (FT) exhibited high integrity (q₀ = 24.3 families), establishing the regional baseline for Andean–Amazonian freshwater ecosystems. In stark contrast, GM sites showed catastrophic defaunation (q₀ = 9.9 families) coupled with extreme turbidity (1320 ± 1589 NTU) and heavy metal mobilization (Fe: 430 ± 229 µg/L; Cu: 338 ± 128 µg/L), placing these reaches in “Bad” ecological status (Ecological Quality Ratio, EQR ≤ 0.16). Wastewater sites reached critical fecal coliform levels (33,708 ± 58,047 CFU/100 mL)—165-fold higher than FT sites—indicating severe sanitary impairment and community collapse (EQR = 0.28, dominated by Chironomidae at 80%). The application of ASPT (Average Score Per Taxon) and EQR proved essential for detecting functional shifts toward tolerant assemblages even when raw biotic scores appeared moderate. Crop/Aquaculture sites showed intermediate degradation (EQR = 0.37–0.38), reflecting chronic pesticide exposure and habitat loss. We conclude that gold mining and wastewater discharge are the primary drivers pushing the UNRB toward ecological collapse, with GM exerting the most severe impact on aquatic biodiversity. Safeguarding this global freshwater stronghold requires immediate implementation of multimetric biomonitoring, enhanced mining regulation, wastewater treatment infrastructure, and establishment of Indigenous-led fluvial reserves to maintain long-term connectivity. Full article

Reconciling hydropower development with aquatic biodiversity conservation is a central challenge for sustainable river management worldwide. Cascade dam configurations, in which multiple impoundments are arranged in series along a single channel, impose longitudinal environmental gradients that restructure biological communities across trophic levels. Whether the resulting multi-trophic responses are independently driven by shared abiotic gradients (environmental filtering) or mechanistically coupled through direct food-web interactions (trophic cascading) remains unresolved. We surveyed phytoplankton, zooplankton, and benthic macroinvertebrates simultaneously at seven stations along a 430 km gradient downstream of Danjiangkou Dam in the Hanjiang River, the largest tributary of the Yangtze River and the source of China’s South-to-North Water Diversion Middle Route, over eight seasonal campaigns (2015–2017). Variance partitioning, piecewise structural equation modeling, Mantel tests, and co-occurrence network analysis were applied to partition environmental and trophic pathways. Environmental filtering dominated community restructuring at all three trophic levels, while the biotic proxy for direct trophic interactions explained less than 0.4% of community variation, consistent with weak detectable trophic coupling at seasonal resolution. Distance from Danjiangkou Dam shaped downstream transparency and turbidity gradients that mediated trophic-level-specific responses along distinct environmental axes (pH and water temperature for phytoplankton, conductivity for zooplankton, and transparency for benthic macroinvertebrates). Benthic macroinvertebrates were systematically decoupled from the pelagic analytical framework, absent from the cross-trophic co-occurrence network and structured more by spatial configuration than by water-column variables. Hub species in the network were associated with downstream mineralized conditions, confirming that network architecture reflects shared environmental preferences rather than biotic interactions. These findings support a management shift from single-dam mitigation toward cascade-scale coordination of environmental flow regimes, sediment connectivity, and substrate restoration as integrated strategies for sustaining multi-trophic biodiversity in regulated rivers. Full article

The Anastasia River (southern Sakhalin Island) is a key salmon spawning ground, where summer storm floods can drastically alter benthic communities that form the diet of fish. This study assessed the impact of heavy rainfall on the benthic macroinvertebrates in the lower reaches of the river by analyzing taxonomic composition, biomass, and fatty acid (FA) profiles of dominant taxa before and after a flood event. A catastrophic decline in biomass was observed (from 35.7 ± 4.4 g m⁻² to 1.74 ± 0.68 g m⁻²), alongside a significant shift in community structure. Crustaceans (dominated by Eogammarus kygi), with a unique FA profile rich in long-chain n-3 and n-6 polyunsaturated fatty acids (PUFAs), were the primary bearers of high nutritional value. All crustaceans exhibited omnivorous diets, with river crabs (Eriocheir japonica) having a broader spectrum than conspecifics inhabiting the marine littoral zone. Amphipods were key processors of allochthonous matter. The flood caused not only a quantitative but also a severe qualitative reduction in community nutritional value, with the content of physiologically crucial n-3 and n-6 PUFAs dropping by a factor of 25 and 15 on average, respectively. The disproportionately high loss of n-3 PUFAs indicates that the qualitative degradation of food resources by extreme floods may be an underestimated factor limiting the post-flood recovery of fish populations. Full article

Understanding nitrogen distribution in spring-fed karst rivers is important for interpreting ecosystem responses in populated Mediterranean landscapes. Nitrogen, in its various forms, is a key physicochemical quality element influencing biological communities and ecological quality of freshwater ecosystems. Elevated nitrogen availability may trigger eutrophication and other processes associated with biodiversity loss, posing risks to both aquatic ecosystem integrity and drinking water quality. However, translating nitrogen measurements into effective monitoring and management strategies remains challenging. Monitoring programs are often resource-intensive and require site-specific adaptation, particularly in heterogeneous systems such as karst catchments. General guideline values may not fully capture local hydrological variability, groundwater–surface water interactions, or combined stressors, including nutrient mixtures and salinity intrusion. These factors introduce uncertainty and complicate the interpretation of nitrogen dynamics. This pilot-scale exploratory study assessed total nitrogen (TN) across four environmental matrices—water and sediments, as well as tissue TN in aquatic bryophytes, and in benthic macroinvertebrates—at four spring-fed sites within the Koiliaris River Basin (Crete, Greece). The Koiliaris Critical Zone Observatory (CZO) is a representative karst watershed with highly permeable carbonate geology and long-term human pressures. TN concentrations were low in water (0.9–1.4 mg/L) and sediments (0.2–1.1 g/kg) but substantially higher in biotic compartments, particularly in macroinvertebrates (29.8–47.1 g/kg), while moss tissue TN ranged between 16.9 and 20.4 g/kg. Spatial variability among sites was observed, with consistently higher TN values at the coastal spring influenced by seawater intrusion. Although the limited sample size precluded formal statistical inference, exploratory analyses indicated positive associations between water TN and tissue TN in mosses and macroinvertebrates. These preliminary findings suggest that dissolved nitrogen may represent an important pathway of nitrogen availability to aquatic biota in this karst system. The study provides an exploratory framework for integrating abiotic and biotic nitrogen measurements and may inform the design of future, larger-scale investigations in Mediterranean spring-fed rivers. Full article

Freshwater bivalves influence ecosystem functioning by transferring pelagic material to the benthos through filtration and biodeposition, yet quantitative multiscale evidence remains scarce for South American lakes. We assessed the role of the native mussel Diplodon chilensis in Laguna Chica de San Pedro (southern Chile) by integrating laboratory measurements, seasonal in situ mesocosm experiments, and lake-scale estimates. Individual filtration rates were quantified under contrasting temperature and phytoplankton biomass conditions, while field experiments evaluated mussel effects on sediment biogeochemistry and zoobenthic assemblages. Filtration increased strongly with temperature, whereas food availability exerted a detectable effect only at lower temperatures. Live mussels consistently enhanced sediment organic matter and total nitrogen, while total phosphorus responses were weak and variable. Macroinvertebrate richness and abundance increased in association with mussel presence, whereas meiofaunal responses were weaker and inconsistent. When scaled to the lake level using bathymetric population distribution and seasonal deposition rates, D. chilensis accounted for substantial annual fluxes of organic matter and nitrogen to surface sediments, largely driven by shallow and intermediate depths. These results demonstrate that native freshwater mussels mediate a persistent downward component of benthic–pelagic coupling in clear-water temperate lakes of southern South America. Full article

Estimating runoff in ungauged catchments remains a major challenge in hydrology, particularly in remote Andean headwaters where limited accessibility and budgetary constraints hinder the long-term operation of monitoring networks. This study integrates satellite-derived rainfall data, hydrological modeling, and benthic macroinvertebrate diversity analysis to explore how short-term antecedent flow conditions relate to temporal variation in community structure. The research was conducted in a pristine 0.26 km² micro-catchment of the upper Collay basin (southern Ecuador). Daily simulated discharge was used to compute antecedent flow descriptors representing short-term variability and cumulative changes in stream conditions, which were related to taxonomic (i.e., H = Shannon diversity, E = Pielou evenness, and D = Simpson dominance) and functional indices (i.e., Rao = Rao’s quadratic entropy, FAD1 = Functional Attribute Diversity, and wFDc = weighted functional dendrogram-based diversity) using Generalized Additive Models. Results showed progressively higher hydrology–biology associations with increasing antecedent flow integration length, suggesting that biological variability responds more strongly to cumulative than to instantaneous flow conditions. Among hydrological descriptors, the cumulative magnitude of negative flow changes was consistently associated with taxonomic diversity. H and E showed more coherent and robust patterns than functional metrics, indicating a faster response of community composition to short-term hydrological variability, whereas functional diversity integrates slower ecological processes. While based on modeled discharge under severe hydrometeorological data limitations, this study provides a practical ecohydrological starting point for identifying short-term hydrological memory signals potentially relevant to aquatic biodiversity in ungauged headwater systems. Full article

River and lake health assessment has evolved from a purely ecological concept to a multidimensional framework integrating ecosystem integrity and social service functions. Based on a comprehensive dataset of 1412 papers (1991–2024), this study combines bibliometric mapping with a systematic review to track the evolution of biological monitoring and assessment methodologies. Quantitative analysis of keywords reveals that while traditional focuses on heavy metals, fish, and sediments remain dominant, there is a significant shift towards integrated frameworks where biological indicators (e.g., benthic macroinvertebrate integrity and fish retention) are increasingly coupled with social services. We critically review three assessment paradigms: single-factor bio-indicators, biological predictive models such as RIVPACS and AUSRIVAS, and multi-factor comprehensive models. The study identifies critical gaps in ecological connectivity and the management of transboundary lakes under climate change. Consequently, we propose a strategic roadmap leveraging the National Ecological Connectivity Optimization Platform and mandatory “health audits” for transboundary waters to ensure the long-term sustainability of aquatic biodiversity. This review provides a scientific basis for balancing biodiversity conservation with sustainable water resource utilization. Full article

Laboratory and field investigations were used to assess the toxicity of leachate from a closed sanitary landfill on benthic macroinvertebrates in coldwater trout streams located near a landfill in southeastern Minnesota, USA. Field-collected invertebrates were exposed to a range of concentrations (0–100%) of leachate during a series of 24 h and 7-day laboratory toxicity tests. Benthic macroinvertebrates also were collected from two stream sites on either side of the landfill and at a third site downstream to assess potential pollution exposure of the stream communities. Ten different taxa exposed to 100% leachate for 24 h exhibited survival ranging from 0 to 100%, with survivorship not correlated to published invertebrate pollution tolerance values. More extensive 24 h tests with the least tolerant Brachycentrus caddisfly larvae found 100% mortality at leachate concentrations > 70%, with the first mortalities observed after 3 h. Brachycentrus had 100% survival at leachate concentrations < 40%. During 7-day tests, Brachycentrus had 100% survival at all leachate concentrations of 40% and lower, but all Brachycentrus died after 2 days at concentrations of 60% and higher. Instream benthic communities, averaging 12 to 17 different taxa at the various stream sites, were rated from good to excellent based on biotic index values, with intolerant taxa present at all three stream sites. Landfill leachate has not impacted the benthic invertebrate communities in streams nearby, but leachate at higher concentrations has the potential to be toxic to a variety of local taxa. Full article

The community structure and ecological niche of benthic macroinvertebrates in the upper Yarlung Zangbo River were analyzed in April and September 2023. The benthic macroinvertebrate community largely comprises aquatic insects, with Diptera accounting for approximately half. Commonly observed were Chironomus anthracinus, Tadamus sp.1, Piscicola geometra, species of the family Corixidae spp. and the genera Monodiamesa sp., Apatania sp., and Valvata sp. in April, and Orthocladius sp.1, Gammarus sp., Isoperla sp., Nais sp., Baetis sp., Monodiamesa sp., Tanytarsus sp., Ilisia sp., Nebrioporus sp. and species of the family Corixidae spp. in September. The α-diversity analysis showed significant seasonal differences (p < 0.05) in Shannon–Wiener diversity variable and Margalef richness variable. The Pielou evenness variable did not show seasonal effects (p > 0.05). The β-diversity April/September differences can be attributed to species turnover rather than to nestedness, indicating that benthic macroinvertebrate diversity protection strategies are critical to all areas of the river. In April, Chironomus anthracinus exhibited the broadest ecological niche, and, in September, the widest niche was observed in Gammarus sp. The largest observed ecological niche overlap values were between Chironomus anthracinus and Valvata sp. in April and Gammarus sp. and Ilisia sp. in September, indicating interspecific competition. The study clarifies the diversity status of benthic macroinvertebrates in the upper Yarlung Zangbo River and provides data for related research to facilitate formulation of biodiversity conservation policies. Full article