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While land use intensification is a major driver of biodiversity change in streams, the nature of such changes, and at which scales they occur, have not been synthesized. To synthesize how land use change has altered multiple components of stream biodiversity across scales, we compiled data from 37 studies where comparative data were available for species’ total and relative abundances from multiple locations including reference (less impacted) streams to those surrounded by different land use types (urban, forestry, and agriculture). We found that each type of land use reduced multiple components of within-stream biodiversity across scales, but that urbanization consistently had the strongest effects. However, we found that β-diversity among streams in modified landscapes did not differ from β-diversity observed among reference streams, suggesting little evidence for biotic homogenization. Nevertheless, assemblage composition did experience considerable species turnover between reference and modified streams. Our results emphasize that to understand how anthropogenic factors such as land use alter biodiversity, multiple components of biodiversity within and among sites must be simultaneously considered at multiple scales.

Neotropical ecosystems are highly biodiverse; however, the excessive use of pesticides has polluted freshwaters, with deleterious effects on aquatic biota. This study aims to analyze concentrations of active ingredients (a.i) of pesticides and the risks posed to freshwater Neotropical ecosystems. We compiled information from 1036 superficial water samples taken in Costa Rica between 2009 and 2019. We calculated the detection frequency for 85 a.i. and compared the concentrations with international regulations. The most frequently detected pesticides were diuron, ametryn, pyrimethanil, flutolanil, diazinon, azoxystrobin, buprofezin, and epoxiconazole, with presence in >20% of the samples. We observed 32 pesticides with concentrations that exceeded international regulations, and the ecological risk to aquatic biota (assessed using the multi-substance potentially affected fraction model (msPAF)) revealed that 5% and 13% of the samples from Costa Rica pose a high or moderate acute risk, especially to primary producers and arthropods. Other Neotropical countries are experiencing the same trend with high loads of pesticides and consequent high risk to aquatic ecosystems. This information is highly valuable for authorities dealing with prospective and retrospective risk assessments for regulatory decisions in tropical countries. At the same time, this study highlights the need for systematic pesticide residue monitoring of fresh waters in the Neotropical region.

Spatio-temporal patterns of four neighbouring river-scapes in the central Western Ghats, India through land-use analyses using temporal remote sensing data (1973, 2018), reveal a decline in evergreen forests (41%) and fragmentation of intact or contiguous forests (60%). Hydro-ecological footprint illustrates that catchment integrity plays a decisive role in sustaining water for societal and ecological needs. This is evident from the occurrence of perennial streams in the catchment dominated by native flora with forest cover greater than 60%, highlighting the riverscape dynamics with hydrological, ecological, social and environmental dimension linkages and water sustainability. This helps in evolving strategies to adopt integrated watershed management to sustain anthropogenic and environmental water demand.

Zooplankton are critical indicators of pressures impacting freshwater ecosystems. We analyzed the response of zooplankton communities across different sub-catchment types—headwaters, natural, urban, urban-agricultural, and agricultural—within the Łyna river–lake system in Northern Poland. Using taxonomic groups and functional traits (body size, feeding strategies), we applied Partial Least Squares Regression (PLS-R) to elucidate the relationships between environmental conditions, land use, and zooplankton metacommunity structure. Two-Way Cluster Analysis (TWCA) identified local subsets with characteristic patterns, while Indicator Species Analysis (ISA) determined area-specific taxa. The natural river zone exhibited significant habitat heterogeneity and feeding niches, whereas urban areas created functional homogenization of zooplankton, dominated by small, broad-diet microphages. Agricultural areas promoted diversity among large filter feeders (Crustacea), active suctors (Rotifera), and amoebae (Protozoa). However, intensified agricultural activities, substantially diminished the zooplankton population, biomass, taxonomic richness, and overall ecosystem functionality. The impact of land cover change is more pronounced at small-scale sub-catchments than at the catchment level as a whole. Therefore, assessing these impacts requires detailed spatial and temporal analysis at the sub-catchment level to identify the most affected areas. This study introduces a new sub-catchment-based perspective on ecosystem health assessment and underscores the zooplankton's role as robust indicators of ecological change.

We analyzed periphyton structure, elemental composition: carbon (C), nitrogen (N) and phosphorus (P), and algal composition along an urban gradient in three water courses of Ushuaia City. We hypothesize that periphyton stoichiometric ratios (C:N, C:P and N:P) decrease with the increase of urban land use. Also, community structure is affected by urban land use; sites with major surrounding urban and higher nutrient load host larger biomass and different algae composition compared to more pristine sites. P content and mass fractions of periphyton increased along the urban gradient as well as dissolved P in the water. Periphyton molar ratios N:P and C:P showed a negative lineal relationship with the gradient of urban land use. In general, periphyton was dominated by diatoms although Chlorophyta biovolume, mainly composed of filamentous algae, increased significantly in sites with 70% of urban land use. Our data suggest that there is no homeostatic balance in the periphyton community in Sub-Antarctic streams; we detected more P in periphyton in urban sites and the community became thus less heterotrophic. This study helps to better understand the dynamics of nutrients and its influence over a sessile community in sub-Antarctic lotic ecosystems impacted by urbanization.

Non-ferrous metals mining activities have long accompanied people, and began in the study area of South East Europe over 2000 years ago. The environment quality is significantly affected by both historic mining activities and contemporary impacts. All these problems, inducing synergic negative effects on local organism communities, have created a chronic state of pollution. The Corna Valley has one of the oldest historical human impacts in Romania due to the influence of mining. Fish and benthic macroinvertebrates have exhibited significant responses to long term mining effects on lotic systems. The analysis of macroinvertebrate communities, correlated with the lack of fish and some biotope characteristics, indicates that the Corna River presents a variety of categories of ecological status between sectors. The lack of fish reveals the poor ecological conditions. Technical and management solutions are proposed here to diminish the historical environmental problems and to avoid future ecological accidents, especially in an attempt to improve any construction plan concerning a possible new de-cyanidation dam and lake. Fish and benthic macroinvertebrates have exhibited significant responses to long term mining effects on lotic systems. Two management zones were identified, an upper zone which can be used as a reference area and a lower zone, where pollution remedial activities are proposed.

The development of environmental DNA (eDNA) methods toward implementation as a cost‐effective, nonlethal tool for fish biomonitoring in lotic environments requires insights on the temporal and spatial distribution of eDNA in river systems. Yet, little is known on how downstream eDNA dispersal is affected by the combination of river discharge and source biomass effects. In this study, we aimed at unraveling the effect of source‐ and system‐specific processes on the stream reach of eDNA. We used a longitudinal cage study in two river sections characterized by a significantly different discharge rate, where two invasive and two native fish species were introduced under two contrasting biomass treatments. Using droplet digital PCR (ddPCR) analyses, we found that eDNA concentrations become strongly reduced 2 km downstream from the source, an effect that is strengthened with increasing river discharge and coinciding dilution effects. Higher discharge rates resulted in equal or even higher detection probabilities at increasing distance from the source. The introduction of high fish stock biomass resulted in an increase of eDNA concentrations, as well as detection probabilities and in parallel reduced the stochasticity of the measurements. A peak in eDNA concentrations at a downstream distance ranging between 300 m and 2 km confirms the complexity of plume‐shaped downstream eDNA patterns. Our results showed interspecific variation in eDNA emission and suggest species‐specific differences in eDNA persistence. This study underlines the impact of both river discharge rate and source biomass on downstream eDNA detection and dispersal patterns. The vast developments of environmental DNA (eDNA) methods to serve as a cost‐effective, nonlethal tool for fish biomonitoring in lotic waters are still limited by empirical insights and challenges including both source‐specific and system‐specific processes affecting the stream reach of eDNA. In this study, we aimed at unravelling the effect of both river discharge rate and source biomass effects on the downstream eDNA dispersal patterns.

Wastewater treatment plants (WWTP) are a crucial part of modern day infrastructure, cleaning about half of our global wastewater. However, the emergence of micropollutants and higher frequencies of extreme weather events pose unprecedented challenges for society and biodiversity. Conventionally treated wastewater and altered flow regimes create environmental boundaries in rivers, impacting aquatic communities. Previous studies revealed pronounced taxonomic changes in freshwater invertebrate communities in response to WWTP effluents. To explore whether these shifts extend to functional diversity, we studied 338 communities upstream and downstream of 169 WWTPs using commonly applied functional diversity metrics. Surprisingly, we found no clear changes in functional alpha and beta diversity metrics, or community weighted means (CWM), suggesting that trait redundancy offsets the functional impact of the previously observed species turnover. However, in streams dominated by Ephemeroptera, Plecoptera and Trichoptera (EPT), we found more pronounced shifts in CWMs, indicating that the extent of functional changes depends on the baseline condition of the streams. EPT-dominated site-pairs showed significant shifts in traits related to reproduction, dispersal, and feeding, including increased occurrences of ovoviviparity and interstitial locomotion potentially as an avoidance mechanism of high flow and low oxygen saturation. Further, shifts in shredding and absorbing feeding types, aquatic passive dispersal, and hololimnic life cycles might be forms of adaptation to increased nutrient concentrations and reduced intermittency induced by WWTPs. These findings demonstrate that functional responses to wastewater inputs can remain undetected due to the noise inherent in large datasets and are often absent as a result of functional redundancy. In contrast, significant changes emerge in communities dominated by sensitive species, underscoring the value of trait-based approaches for detecting context-dependent ecological impacts.

Ditches are widespread and common elements of the agricultural landscape. Although they can provide habitats for aquatic biodiversity, their ecosystem integrity and processes are generally limited or even unknown due to anthropogenic pressures and the paucity of studies on this type of aquatic ecosystem. This study aimed to enhance the knowledge on the biodiversity, ecosystem attributes and ecological status of agricultural ditches by analyzing the macroinvertebrate communities of six different ditches and those of the main river in the same area. While negligible differences in taxonomic richness were observed, macroinvertebrate community composition significantly varied among sites as a function of the heterogeneous habitat conditions. These compositional differences strongly affected the relative abundance of functional feeding groups among sites and their derived ecosystem attributes. Moreover, the ecological status assessment depicted different scenarios depending on the biomonitoring indices applied. By means of a multifaceted, but still poorly adopted, analysis of the macroinvertebrate community, ranging from the taxonomic and functional diversity to ecosystem attributes and biomonitoring indices, the results obtained in this study offer useful information on the ecology of agricultural ditches with potential insights to improving their management.

Agriculture is one of the main factors associated with global biodiversity loss. The present study assesses the impact of horticultural land use on water quality and fish assemblage composition in lowland Pampean streams. Four samplings were conducted with seasonal frequency during 2018 and 2019 in three horticultural stream reaches (HSR) and three grassland reaches (GSR) with low anthropic intervention, two also located in a biosphere reserve area. Environmental parameters were determined, and water and sediment samples were taken for nutrient and pesticide analysis, respectively. Fish assemblages were sampled in two habitat types: open water (OW) and vegetated patches (VP). The concentration of soluble reactive phosphorus and the detection frequency and concentration of pesticides were significatively higher in HSR mainly attributed to the runoff events following application of fertilizers and pesticides to the surrounding crops. Specific richness was significantly higher in GSR for both OW and VP environments. Diversity and evenness in the VP were significantly higher in GSR, while abundance was significantly higher in HSR due to the dominance of the environmental pollution-tolerant taxa of the order Cyprinodontiformes. The multivariate analysis recorded a major contribution of the order Cyprinodontiformes in the HSR, while the GSR species of the order Characiformes, common in environments of low environmental impact, were better represented. Our study demonstrated water quality deterioration associated with horticultural land use resulting in a ruderal fish community. On-going horticulture expansion is expected to cause further deterioration within the region, unless managerial practices are implemented.