Search Results (508)

Water temperature is a key ecological and metabolic factor in rivers and other continental systems, and thermal pollution caused by anthropogenic activities (dams, discharges, urban stormwater, industrial cooling) alters the natural thermal regime of rivers, modifying the structure and functioning of communities (primary producers, macroinvertebrates and fish) and favouring thermophilic and often invasive species. Wastewater treatment plants (WWTPs) generate and discharge excess heat: their effluents are often several degrees above the temperature of the receiving river, which increases the metabolism of communities, favours eutrophication and can intensify the effects of nutrients and toxic pollutants. This excess heat from wastewater is a major renewable energy resource that can be recovered using heat pumps, both in buildings and in the treatment plants themselves, as well as in district heating networks, reducing the demand for fossil fuels and CO₂ emissions. Heat recovery in WWTPs, especially from treated effluent connected to district networks, offers very high technical potential (tens of TWh per year on a national scale in some countries) and can contribute significantly to more sustainable urban energy systems. Heat recovery in WWTPs can minimize the thermal impact of effluents on receiving rivers, reducing the negative effects of discharges on the natural environment. 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

Plastic pollution is ubiquitous in the environment, with microplastics (particles < 5 mm) a worldwide emergent contaminant of concern; however, no studies have explored historical patterns in freshwater macroinvertebrates in connection to species traits and changes in land use. We measured microplastics in macroinvertebrates collected from 1998–2019 at six forest, urban, and agriculture dominated streams in the Schuylkill River watershed (PA, USA). We selected representative macroinvertebrates that underwent peroxide oxidation digestion and were examined for microplastics under a dissecting microscope with Rose Bengal dye to confirm microplastic identification. Microplastics were present in 134 individuals across 24 taxa and all functional feeding groups (FFGs). Abundance of microplastics in macroinvertebrates decreased through time with an increase of agriculture land use, whereas microplastics increased with an increase of urban land use. Collector-gatherer FFG had the greatest microplastic abundance, which may be linked to Elmidae and Psephenidae (Coleoptera), which tended to have the highest abundances of microplastics compared to all other taxa in some years. This relationship may be explained by the feeding mode of these families of macroinvertebrates and that gathering particles in the water column and scraping particles from biofilms may be similarly effective in the acquisition of microplastics. Overall, understanding microplastic temporal patterns and their connections to species traits and variations in land and water use is critical to developing a predictive framework for explaining microplastic abundance in the environment and interactions with aquatic biota. 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

As the largest tributary of the Yangtze River and a core area of the Middle Route of the South-to-North Water Diversion Project, the Han River Basin holds significant ecological importance regarding the impacts of land use and water environment changes on aquatic ecosystems. Existing studies have mostly focused on local reaches of the upper or middle–lower Han River, and systematic investigations into the associations between macroinvertebrate communities and environmental factors at the entire basin scale remain scarce. The niche characteristics and environmental drivers of macroinvertebrate community structure in the Han River Basin, China, were evaluated using a variety of diversity metrics and statistical methods. The results showed that: (1) A total of 91 macroinvertebrate taxa were identified during 2022–2023, with Insecta as the dominant group. Species richness in the upstream reaches increased in 2023, and the degree of differentiation between the upstream and the middle–lower reaches was markedly weaker than that in 2022. (2) Significant interannual differences in macroinvertebrate community structure were detected (PERMANOVA, p < 0.05), and taxa such as Polypedilum sp., Orthocladius sp., and Gammaridae collectively accounted for 35.6% of the dissimilarity among communities. (3) The overall niche breadth of dominant taxa was relatively low, whereas niche overlap decreased significantly in 2023, indicating a community niche pattern characterized by “low competition–high differentiation”. (4) Total phosphorus (TP) and total nitrogen (TN) were the core water environmental factors driving changes in community structure, while forested land was the key land use factor, and their synergistic effects jointly regulated the composition and diversity of macroinvertebrate communities. Full article

Fire refugia are critical for post-disturbance recovery, yet microhabitats such as stones remain understudied despite their ubiquity and thermal persistence. This study tested whether the depth- and area-dependent refugial capacity of stones previously demonstrated in Mediterranean oak forests also operates in intensively managed plantations and how forest type and management modulate this capacity. Immediate wildfire effects (1–8 days post-fire) on ground-dwelling macroinvertebrates were quantified under 660 stones across burnt and unburnt native maritime pine and exotic eucalypt plantations following a medium- to high-severity wildfire. Stones acted as thermal refugia in both plantation types, with burial depths greater than 5 cm and surface areas greater than 500 cm² predicting survival. Despite severe impacts (richness declined by 56% in pine and 63% in eucalypt; overall mortality exceeding 50%), diverse taxa persisted under stones, particularly ground spiders, ants, centipedes, rock bristletails, and harvestmen, while plant-associated and moisture-dependent groups suffered the highest losses. Native pine supported a higher abundance and richness per stone than exotic eucalypt in both burnt and unburnt conditions, reflecting management-driven differences in stone size, depth, and availability. These findings show that retaining sufficiently large, deeply buried stones during plantation establishment can enhance post-fire biodiversity recovery in increasingly fire-prone production landscapes. Full article

Both riparian tree species diversity and genetic diversity can influence streams through leaf litter decomposition; however, these two sources of variation have not been compared directly. Here, we compare leaf litter decomposition for a physical mixture of two Populus species to the litter from an F₁ hybrid (a genetic mixture) of the same two species. Leaf litter was collected from a common garden for an F₁ hybrid between Japanese poplar (Populus maximowiczii A. Henry) and black cottonwood (Populus trichocarpa Torr. & A. Gray ex Hook.), as well as both parent species. Four litterbag treatments consisted of litter from the F₁ hybrid, an equal-part mixture treatment of litters from both parents, and litter from each parent in isolation. The hybrid litter had higher C:N content and lower % condensed tannins than either parent species, or the average of the two parents that represented the mixture. While the hybrid and mixture treatments both lost more mass than expected by day 42, the mixture lost relatively more mass than the hybrid and roughly as much as the faster-decomposing P. trichocarpa parent. The hybrid mimicked the mixture, and both supported higher aquatic macroinvertebrate richness and less litter mass remaining than expected based on parent species values, despite differences between the hybrid and mixture in initial phytochemistry. Full article

Artificial water bodies in post-mining landscapes often remain chemically altered and ecologically degraded, yet their ecological risk is frequently underestimated by conventional water quality assessments. Persistent toxicity in mining-impacted waters is a global challenge, as acidity alone often fails to explain the adverse biological effects observed. This study assessed the ecological condition of three artificial ponds in a former gold–antimony mining area (Midões, northern Portugal), using an integrated framework that combined physicochemical and biological (phytoplankton and macroinvertebrates) elements with ecotoxicological assays. Ecotoxicity was evaluated using Lemna minor (growth inhibition) and Daphnia magna (acute toxicity, survival, and feeding rate) under untreated water and pH-adjusted conditions to disentangle acidity-driven effects from other chemical stressors. According to Water Framework Directive metrics, all ponds were classified as having moderate ecological potential, driven by persistent acidic conditions and elevated heavy metal concentrations (e.g., zinc and cadmium). Biological communities showed marked temporal/spatial variability, reflecting physicochemical differences among ponds. Phytoplankton showed summer blooms of cyanobacteria, while macroinvertebrates were generally dominated by tolerant taxa (exhibiting low taxonomic richness/diversity). Ecotoxicological assays showed consistent toxicity across all sampling periods, with high mortality and reduced feeding rates in D. magna and growth inhibition in L. minor. Notably, toxicity often persisted even after pH adjustment, indicating that the observed biological effects were not driven by acidity but were largely attributable to residual metal contamination. These findings highlight the ecological vulnerability of mining-impacted water bodies and underscore the need for management and remediation strategies that address metal removal in addition to pH correction. Full article

Despite reductions in sulphur and nitrogen emissions, lakes and streams in Europe and North America have shown only partial recovery from acidification. This study aims to assess the chemical and biological recovery of the upper stretch of the Litavka River, currently on of the most acidic stream in the Czech Republic. Water composition and macroinvertebrates were studied for 1999, 2010, and 2021, along with long-term data on hydrology and climate. Over these 22 years, concentrations of SO₄²⁻, base cations, conductivity, and toxic Al forms (Al_i) significantly decreased, but pH only increased from 4.2 to 4.3. Biological recovery was most evident during 1999–2010, with an increase in the number of taxa and the appearance of less acid-tolerant taxa such as stonefly Diura bicaudata and caddisfly Rhyacophila sp., mainly associated with decreased Al_i toxicity. Subsequently, however, despite continued chemical improvement, macroinvertebrate diversity decreased, and sensitive taxa were again absent in 2021. Average annual temperature increased by 2.4 °C over the past 50 years (1970–2020) while precipitation remained unchanged, resulting in significant aridification of the regional climate. We attribute the lack of biological recovery in 2021 to climate-related changes, including more frequent dry periods and floods. Although partial biological recovery of the river followed chemical recovery, the increasing frequency of hydrological extremes has likely become the main limiting factor. 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

Tributary-to-mainstem discontinuities (TMDs) are understudied, but are likely common in river networks, arising from abrupt transitions in stream order and dominant ecological factors. We present a conceptual model of aquatic macroinvertebrate (AMI) TMD directionality and relative magnitude by contrasting the impacts of hydrography, geochemistry, and sediment transport on tributary-related channel-floor precipitate cementation and the mainstream embeddedness (burial) of channel-floor substrata in fine sediment. We test that model using AMI assemblage density/m², species richness/sample, and diversity data from 24 tributaries confluent with the regulated Colorado River in Grand Canyon through pairwise and multivariate analyses of long-term discharge records and substrate and water-quality data in three habitats: tributaries, their confluences, and adjacent mainstream habitats. Mean AMI density decreased 2.7-fold from low to high cementation, 6.1-fold from low-to-high embeddedness, and 136.0-fold across combined gradients. We also analyzed pre-dam aquatic insect literature, finding that TMDs were naturally common in Glen Canyon upstream but were more strongly tributary-positive (discontinuity magnitude, D_mag = 0.62 in pre-dam Glen Canyon) compared to tributaries in the post-dam Grand Canyon (D_mag = 0.31). We conclude that, depending on D_mag directionality, tributary confluences can function as hotspots or barriers to AMI assemblage development. Our results demonstrate that TMDs are and were common in the contemporary regulated and natural unregulated Colorado River corridor, and we expand the concept of biotic discontinuity to improve understanding of fluvial ecosystem ecology and constraints on river and dam management. 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