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Stoneflies are a globally threatened aquatic insect order. In Arkansas, a diverse group of winter stonefly (Capniidae: Allocapnia) have not been surveyed since the 1980s, likely because species-level identification requires the rarely-collected adult form. Allocapnia mohri, a regional endemic, was previously commonly found in mountainous, intermittent streams from the Ouachita Mountains ecoregion north to the Ozark Highlands, but no species distributional models including land use or climate variables exist to our knowledge. We collected adults from 71 stream reaches from the historic Arkansas range from November to April 2020 and 2021. We modeled distributions using random forest (RF) models populated with landscape, climate, and both data to determine which were most predictive of species presence. Correlations between landscape or climate variables and presence were examined using multiple logistic regression. The landscape RF models performed better than the climate or landscape + climate RF models. A. mohri presence sites tended to have a greater elevation, a lower mean July temperature, and a greater percentage of very slow infiltration soils in the watershed, compared to absence sites. A. mohri was absent at the Ouachita Mountains sites and may be experiencing a range contraction or migration northward.

Aim: Biodiversity changes can occur gradually or as distinct jumps as species distributions end and others begin. However, comprehensive assessments of freshwater biodiversity and how assemblages change along a continuum have been hindered by the connectivity and networked nature of streams and their large numbers of rare and cryptic species found there. We hypothesize that the boundary where fish distributions end marks an ecological shift in freshwater assemblages and could unify stream concepts. Location: Trask River watershed, Oregon, USA, temperate North America. Taxon: Fishes, amphibians, crayfishes, bivalves, mammals, pathogens. Methods: We targeted freshwater species across taxa using multigene eDNA metabarcoding of 48 different DNA barcodes to identify assemblages to understand species patterns distributed along a longitudinal gradient in watersheds around the upper fish distribution boundary. Detections from multiple genetic sources improve the detection probability for rare species. Results: We detected a shift in the assemblage from lower reaches towards headwaters where fish distributions end, leading to fewer species across taxa at reduced eDNA signal. We uncovered a hidden biodiversity in watersheds by detecting a sparsely distributed amphibian pathogen Batrachochytrium dendrobatidis, the elusive mammal Mountain Beaver, fish species that went undetected using traditional approaches, and newly discovered cryptic lineages of sculpins. Salmonids were detected further upstream with eDNA than expected. Main conclusions Our findings unify stream concepts owing to the marked species shift at the upper extent of fish elevating the importance of this boundary. The detection of salmonids further upstream suggests a distribution extension. The sculpin detections reveal a cryptic species complex with ramifications for fish conservation, potential pockets of endemism and possible identification of new species. We show extensive diversity in watersheds, some of which was previously hidden, transforming our understanding of species presence and distributions affecting our ability to track, protect and manage them across watersheds. [ABSTRACT FROM AUTHOR]

Human land‐use change is a major threat to natural ecosystems worldwide. Nonetheless, the effects of human land‐uses on the structure of plant and animal assemblages and their functional characteristics need to be better understood. Furthermore, the pathways by which human land uses affect ecosystem functions, such as biomass production, still need to be clarified.We compiled a unique dataset of fish, arthropod and macrophyte assemblages from 61 stream ecosystems in two Neotropical biomes: Amazonian rainforest and Uruguayan grasslands. We then tested how the cover of agriculture, pasture, urbanization and afforestation affected the taxonomic richness and functional diversity of those three species assemblages, and the consequences of these effects for animal biomass production. Single trait categories and functional diversity were evaluated, combining recruitment and life‐history, resource and habitat‐use, and body size.The effects of intensive human land‐uses on taxonomic and functional diversities were as strong as other drivers known to affect biodiversity, such as local climate and environmental factors. In both biomes, the taxonomic richness and functional diversity of animal and macrophyte assemblages decreased with increasing cover of agriculture, pasture, and urbanization. Human land‐uses were associated with functional homogenization of both animal and macrophyte assemblages. Human land‐uses reduced animal biomass through direct and indirect pathways mediated by declines in taxonomic and functional diversities.Our findings indicate that converting natural ecosystems to supply human demands results in species loss and trait homogenization across multiple biotic assemblages, ultimately reducing animal biomass production in streams. [ABSTRACT FROM AUTHOR]

Water and wastewater laboratories have many similarities, but they also have unique differences that allow them to generate data that protect public health and the environment. [ABSTRACT FROM AUTHOR]

Ecological restoration is a value‐driven process; yet social understanding of restoration lags ecological understanding. Restoration goals are driven by which stakeholders have a voice in the restoration process and their individual goals. While conflict among stakeholder visions has been observed, we lack a multidimensional understanding of these visions, where they overlap, and how they diverge. Focusing on stream restoration on private lands, we asked: (1) How do perspectives on measures of restoration success vary among stakeholders, including contractors and designers, scientists, organizations, and landowners? and (2) How do these groups discuss and navigate these differences? We used a mixed‐method interview and Q‐methodology approach to understand the range of stakeholders' approaches for assessing a successful stream restoration. We asked stakeholders to rank their level of agreement with 33 statements about restoration goals, using these to evaluate perspectives about restoration success. We identified four perspectives on successful stream restoration that varied in: the use of science‐driven criteria, risk tolerance, private property protection, and commitment to restoring streams to a previous state. Notably, contractors used deficit model approaches to communicate with landowners, even for private restoration. Institutional and cultural changes to how we approach restoration, suggested by some of the interviews, may provide paths forward. These include a recognition that all restoration objectives are socially defined, even within and among professionals, and that landowners have important local‐system knowledge. Earlier engagement between all stakeholders involved in restoration may help create mutual understanding across parties and stave off disputes about project objectives or implementation. [ABSTRACT FROM AUTHOR]

The biodiversity of stream fishes is critically threatened globally, and a major factor leading to the loss of biodiversity is anthropogenic land use in stream catchments, which act as stressors to stream fishes. Declines in the biodiversity of stream fish are often identified by a loss of species or fewer individuals comprising assemblages, but biological degradation can also occur with increases in non-native species and/or the spread of fish tolerant to anthropogenic land use, suggesting the importance of accounting for the distinctness of assemblages along with richness and diversity to best characterize the response of stream fish assemblages to anthropogenic landscape stressors. We summarized stream fish assemblages from 10,522 locations through multiple biodiversity indices and then quantified index responsiveness to natural landscape variables and anthropogenic land use in stream network catchments across five freshwater ecoregions in the temperate mesic portion of the United States. Indices included species richness, Shannon's diversity, Pielou's evenness, beta diversity, taxonomic diversity, and taxonomic distinctness. First, we tested for correlations among indices across freshwater ecoregions and found that while species richness and Shannon's diversity were always highly correlated, taxonomic distinctiveness was not highly correlated with other biodiversity indices measured except taxonomic diversity. Then, we used multiple linear regression to predict biodiversity indices in each of the five freshwater ecoregions to identify significant landscape variables from natural landscape and anthropogenic land uses. Most indices were consistently predicted by catchment area, and many were predicted by elevation, except for beta diversity, emphasizing the importance of these natural landscape variables on biodiversity. In contrast, taxonomic distinctness was often predicted by the amount of urban land use in the catchment, but the direction of the relationship varied. The proportion of agriculture land use in the network catchment was a more consistent predictor of species richness, beta diversity, and Shannon's diversity. Our analyses show that taxonomic distinctness in freshwater fishes characterize a unique element of biodiversity in relationships with anthropogenic land uses in a streams network catchment. Taxonomic distinctness may also be an effective metric for the bioassessment of stream fishes along with richness and diversity indices to help preserve biodiversity in regard to current and future anthropogenic land uses. [ABSTRACT FROM AUTHOR]

Ongoing global warming is expected to alter temperature-dependent processes. Nevertheless, how co-occurring local drivers will influence temperature sensitivity of plant litter decomposition in lotic ecosystems remains uncertain. Here, we examined the temperature sensitivity of microbial-mediated decomposition, microbial respiration, fungal biomass and leaf nutrients of two plant species varying in litter quality. We also assessed whether the type of microbial community and stream water characteristics influence such responses to temperature. We incubated alder (Alnus glutinosa) and eucalypt (Eucalyptus globulus) litter discs in three streams differing in autumn–winter water temperature (range 4.6–8.9 °C). Simultaneously, in laboratory microcosms, litter discs microbially conditioned in these streams were incubated at 5, 10 and 15 °C with water from the conditioning stream and with a water control from an additional stream. Both in the field and in the laboratory, higher temperatures enhanced litter decomposition rates, except for eucalypt in the field. Leaf quality modified the response of decomposition to temperature in the field, with eucalypt leaf litter showing a lower increase, whereas it did not in the laboratory. The origin of microbial community only affected the decomposition rates in the laboratory, but it did not modify the response to temperature. Water quality only defined the phosphorus content of the leaf litter or the fungal biomass, but it did not modify the response to temperature. Our results suggest that the acceleration in decomposition by global warming will be shaped by local factors, mainly by leaf litter quality, in headwater streams. [ABSTRACT FROM AUTHOR]

Algae have a long history of use in indicating ecological condition of streams and lakes. Various algae-based indicators have been developed and used in stream and lake water quality management of nutrient pollution. The aim of this work is to synthesize recent studies on using diatom indicators to assess effects of nutrient pollution in streams and lakes worldwide. Here we have reviewed the advancement of the use of diatoms in: (1) assessing the stream and lake conditions by multimetric index (MMI) method, (2) modeling excessive algal dominance in waters, and (3) tracking changes of eutrophication status of lakes. Lots of progress has been made on using algae to evaluate the condition of streams and lakes by MMI method in terms of assessment consistency and accuracy in recent years. Researchers have largely solved consistency issues of assessment from sampling design to MMI development in face of great ecological diversity. Site-specific modeling can improve assessment accuracy either in streams or in lakes. However, more studies are needed to evaluate the importance of varying diatom metrics and site classification by diatom typology. Hence, it is valuable to address to what extent the biological condition of streams and lakes are represented by diatom metrics under different levels of human disturbance. The close relationship between diatoms and other algae makes diatom metrics better predictors for modeling excessive dominance of algae than commonly used physical and chemical variables. Existing studies showed inferred-total phosphorus based on diatoms performed better on predicting Cladophora condition in streams than on modeling cyanobacteria biomass in lakes. However, more studies are needed to accurately evaluate the performance of diatom-based metrics on modeling algal dominance in streams and lakes. Using diatom-based quantitative reconstructions to track environmental change in paleolimnology is meaningful but not without problems. Therefore, we also reviewed effects of some "unconventional" environmental factors on quantitative reconstructions, such as upstream water of lakes and invasive species. [ABSTRACT FROM AUTHOR]

Thiamine (vitamin B1) and its precursor 2‐methyl‐4‐amino‐5‐hydroxymethylpyrimidine (HMP) have been shown to exert an important influence on primary production in marine environments, but little is known about their influence in fresh waters.We evaluated the ecological effects of thiamine and one of its precursors HMP in streams within the Qiyun catchment, a headwater mountain system of a Yangtze River tributary in Southern China, using nutrient‐diffusing substrates.Thiamine limitation of periphyton was observed in April 2019, and HMP limitation was observed in both April and May 2019. Co‐limitation by thiamine plus phosphorus and by HMP plus nitrogen occurred in May. The effect sizes of thiamine and HMP on growth of periphyton were similar to each other.Physiochemical features of the stream showed different potential influences on the effects of thiamine and HMP. Water temperature was negatively associated with the effect of thiamine, whereas ammonium showed a negative relationship with the effect of HMP.These findings extend our knowledge of nutrient limitation by thiamine and one thiamine precursor in freshwater environments. [ABSTRACT FROM AUTHOR]

Data from a bathymetric mapping project conducted in seven Israeli coastal micro-estuaries (Lachish, Sorek, Yarkon, Alexander, Hadera, Taninim, and Kishon) is presented. The data were collected by rowing a kayak along an S-shaped track through the estuaries. An echosounder equipped with a Global Positioning System (GPS) unit were mounted on the kayak. The data preparation consisted of a) manual removal of outliers, mostly caused by instrument echo in water depths below the instrument's 0.5 m minimum; b) correction of the measured water level to sea level; and c) interpolation of the sampling points into a regular grid using a terrain-following interpolation algorithm. For each of the estuaries, the raw measurements as a text (csv) file and the interpolated data both as a text (CSV) file and a GeoTiff file were produced.

Functional diversity (FD) is useful for the evaluation of freshwater ecosystems. The FD of macroinvertebrate families for river water quality (WQ) assessment in the Paute River Basin (PRB), Ecuador, was investigated. Macroinvertebrate samples and data about 26 physical, chemical, microbiological and hydro-geomorphological variables were available. Literature-based biological traits were allocated as scores to the macroinvertebrates data through fuzzy coding. The Generalised Additive Mixed Model (GAMM) was used to assess the performance of six FD indices using the referred 26 WQ descriptive variables. The best performing GAMM led to selecting the index based on functional dendrograms including the species community pool (wFDc) as the most suitable to characterise FD in the PRB. The sub-basins of the PRB were grouped in three classes applying Average Linkage Clustering (ALC) and using wFDc. The Random Forest (RF) algorithm was used with a global efficiency of 89% to assess the ALC clusters consistency and pre-identify the significant WQ descriptive variables, explaining most of the FD variability. The Kruskal-Wallis test was then applied to refine the outcomes of the previous analysis. Twelve WQ descriptive variables were finally identified as the best discriminant predictors for FD, including the riparian vegetation, electric conductivity, dissolved oxygen, total hardness, faecal coliforms and pH. It is believed that the implemented approach successfully assessed the stream WQ status of the PRB upon selecting a suitable macroinvertebrate FD index; as such, it could be applied to other tropical basins for WQ assessment.

Discoveries of endemic species highlight areas of biogeographic and conservation interest. Endemic species, however, are often morphologically disguised as more common and widespread species. The larval polytene chromosomes revealed a new species of black fly, Prosimulium fungiforme, from the Djurdjura Mountains of northern Algeria, and its female, male, pupa, and larva are described. The species is chromosomally unique; none of its 11 chromosomal rearrangements are shared with other species. Although the new species structurally resembles Prosimulium rufipes (Meigen) with which it previously has been confused, it can be distinguished from all other known species of Prosimulium in the Western Palearctic based on at least one character in each described life stage. Symbiotic organisms included two species of microsporidia, at least one of which is probably undescribed, one unknown protozoan pathogen novel in simuliids, and the trichomycete fungus Harpella melusinae Léger and Duboscq. Associated simuliid species included at least one new species of the genus Helodon. The new species of Prosimulium is tentatively considered endemic to the mountains of northern Algeria but might be expected in the mountains of eastern Morocco and northern Tunisia and perhaps in Sicily. If its endemic status holds, it would be the only nominal species of black fly unique to Algeria.

Trash impairment of watersheds has been recognized as a worldwide environmental problem. Trash monitoring in streams and rivers is necessary to enhance our understanding of its effects on freshwater habitats and the role of streams as a conduit for transport to marine environments. Southern California, with a population of over 22 million, is home to nearly 7,400 km of wadeable streams in watersheds spanning a variety of land uses, making it an ideal region to study the extent and magnitude of trash and trash types (plastic, metal, glass, etc.) and identify relationships between land use and the amount of trash. These data can be used to develop mitigation strategies and evaluate management successes. We found that 77% of Southern California’s coastal stream kilometers contained trash, with an estimated stock of 7 million pieces of trash. Of the types enumerated, plastic trash was the most ubiquitous, present in 69% of stream kilometers, and the most abundant, with an estimated stock of over 4.3 million pieces of plastic. The most common items were single-use plastic containers, wrappers, and plastic bags. Urban land use was associated with the greatest extent and magnitude of trash, with levels nearly double those found in open land uses. Trash was strongly associated with indicators of human activity and development in watersheds. Road density and proximity to roads and parking lots were strongly associated with increased trash in watersheds. This survey also suggested that management actions had a positive effect on trash count. After the previous trash survey in Southern California streams in 2011–2013, a statewide ban on plastic bags was implemented in 2016. We found a significant decrease in the number of plastic bags within streams in the present survey compared to the previous survey.

The aquatic, invasive New Zealand mud snail (Potamopyrgus antipodarum) exploits a variety of food sources. Here we examine the change in growth of snails that fed on periphyton colonizing leaf litter, wood, rock, and a control. Juveniles were grown in the lab on Spirulina algae powder (control) or periphyton grown on rock, leaf litter, or wood. Length was measured at the beginning of the experiment and after eight weeks. Snails grown on leaf litter increased in length more than twice as much as the control and the snails in the rock treatment, and the snails grown on wood showed an increase in length more than twice as much as snails in the rock treatment. This suggests that allochthonous material may contribute to a more nutritious food source for New Zealand mud snails and possibly aid in their invasion success.

Simple Summary: A machine learning algorithm, Random Forest, was used to establish species distribution models for five riffle beetle genera (Elmidae) in the Paute river basin (southern Ecuador), considering meteorology, land use, hydrology, and topography as environmental/explanatory variables. Alterations to riparian vegetation, canopy presence/absence, precipitation, elevation, and slope accounted for most of the Elmidae spatial variability. Clean and healthy streams were predicted to be the most likely places for Elmidae genera to occur. Additionally, specific ecological niches were predicted for each Elmidae genus. These findings can contribute significantly to conservation and restoration efforts in the study basin and could have implications for similar eco-hydrological systems. Genera and species of Elmidae (riffle beetles) are sensitive to water pollution; however, in tropical freshwater ecosystems, their requirements regarding environmental factors need to be investigated. Species distribution models (SDMs) were established for five elmid genera in the Paute river basin (southern Ecuador) using the Random Forest (RF) algorithm considering environmental variables, i.e., meteorology, land use, hydrology, and topography. Each RF-based model was trained and optimised using cross-validation. Environmental variables that explained most of the Elmidae spatial variability were land use (i.e., riparian vegetation alteration and presence/absence of canopy), precipitation, and topography, mainly elevation and slope. The highest probability of occurrence for elmids genera was predicted in streams located within well-preserved zones. Moreover, specific ecological niches were spatially predicted for each genus. Macrelmis was predicted in the lower and forested areas, with high precipitation levels, towards the Amazon basin. Austrelmis was predicted to be in the upper parts of the basin, i.e., páramo ecosystems, with an excellent level of conservation of their riparian ecosystems. Austrolimnius and Heterelmis were also predicted in the upper parts of the basin but in more widespread elevation ranges, in the Heterelmis case, and even in some areas with a medium level of anthropisation. Neoelmis was predicted to be in the mid-region of the study basin in high altitudinal streams with a high degree of meandering. The main findings of this research are likely to contribute significantly to local conservation and restoration efforts being implemented in the study basin and could be extrapolated to similar eco-hydrological systems. [ABSTRACT FROM AUTHOR]

Saprotrophic fungi play important roles in transformations of carbon (C), nitrogen (N), and phosphorus (P) in aquatic environments. However, it is unclear how warming will alter fungal cycling of C, N, and P. We conducted an experiment with four aquatic hyphomycetes (Articulospora tetracladia, Hydrocina chaetocladia, Flagellospora sp. and Aquanectria penicillioides), and an assemblage of the same taxa, to test how temperature alters C and nutrient use. Specifically, we evaluated biomass accrual, C:N, C:P, δ13C, and C use efficiency (CUE) over a 35-d experiment with temperatures ranging from 4ºC to 20ºC. Changes in biomass accrual and CUE were predominantly quadratic with peaks between 7ºC and 15ºC. The C:P of H. chaetocladia biomass increased 9× over the temperature gradient, though the C:P of other taxa was unaffected by temperature. Changes in C:N were relatively small across temperatures. Biomass δ13C of some taxa changed across temperatures, indicating differences in C isotope fractionation. Additionally, the 4-species assemblage differed from null expectations based on the monocultures in terms of biomass accrual, C:P, δ13C, and CUE, suggesting that interactions among taxa altered C and nutrient use. These results highlight that temperature and interspecific interactions among fungi can alter traits affecting C and nutrient cycling. [ABSTRACT FROM AUTHOR]

Stoneflies are a globally threatened aquatic insect order. In Arkansas, a diverse group of winter stonefly (Capniidae: Allocapnia) have not been surveyed since the 1980s, likely because species-level identification requires the rarely-collected adult form. Allocapnia mohri, a regional endemic, was previously commonly found in mountainous, intermittent streams from the Ouachita Mountains ecoregion north to the Ozark Highlands, but no species distributional models including land use or climate variables exist to our knowledge. We collected adults from 71 stream reaches from the historic Arkansas range from November to April 2020 and 2021. We modeled distributions using random forest (RF) models populated with landscape, climate, and both data to determine which were most predictive of species presence. Correlations between landscape or climate variables and presence were examined using multiple logistic regression. The landscape RF models performed better than the climate or landscape + climate RF models. A. mohri presence sites tended to have a greater elevation, a lower mean July temperature, and a greater percentage of very slow infiltration soils in the watershed, compared to absence sites. A. mohri was absent at the Ouachita Mountains sites and may be experiencing a range contraction or migration northward. [ABSTRACT FROM AUTHOR]

The modification of landscapes surrounding water bodies leads to changes in limnological characteristics and decreased aquatic biodiversity, such as fish and macroinvertebrates. Aquatic insects are sensitive to changes in aquatic ecosystems and quickly respond to those changes. The aim of this paper was to evaluate the relationship between the compositions of aquatic and semi-aquatic Heteroptera with environmental variables along an environmental gradient in streams at the headwaters of the Xingu River, Brazil. We collected samples from 12 streams belonging to the Suiá-Miçú river basin and tributaries of the Xingu River, in September (dry season), 2008. The Suiá-Miçú river is one of the tributaries on the right bank of the Xingu River, and it is located in the ecotone between the Cerrado and the Amazon rainforest in the area characterized as the "arc of deforestation". Insects were sampled in fixed 100 m transections and divided into 20 segments of 5 meters each. To assess the habitat integrity in each stream, the habitat integrity index (HII) was applied. The following environmental variables were measured: electrical conductivity, turbidity, depth, and the normalized difference vegetation index (NDVI). The ordering of species composition was performed with the principal coordinate analysis (PCoA), and the relationship between environmental variables and composition was performed using a Mantel test. Of the 263 individuals collected, distributed in 8 families, there were 20 genera, of these, 12 were from Nepomorpha and 8 from Gerromorpha. The most abundant genera were Limnocoris (n = 121) and Rhagovelia (n = 32). Naucoridae was the most diverse family. Together, the environmental variables explained ~50% of the species distribution (r = 0.49; p = 0.001). These results reinforce the efficacy of aquatic Heteroptera to monitor environmental conditions. Here, in particular, the responses of this group to variations in landscape metrics, environmental integrity, and water variables together demonstrate that it can be useful to indicate the quality of habitat in streams. [ABSTRACT FROM AUTHOR]

Field trials were conducted to assess the potential for stocking native unionid mussels in urban streams of the Chesapeake Bay catchment. Juvenile, hatchery‐raised mussels were placed in enclosures at five urban streams (two restored and three unrestored) and two nearby rural streams. Adult mussels were translocated to two restored urban streams. Mussel growth and survivorship were assessed at the stream sites and for individuals maintained at hatchery ponds.At all sites, water quality conditions were generally suitable for mussels with respect to temperature, pH, and dissolved oxygen. Food resources, as indicated by the quantity and quality of suspended and benthic particulate matter, were higher among rural sites and lower in unrestored urban streams.Positive growth rates were observed at all sites, among both juveniles (caged) and translocated adults. Mussel fatty acid profiles were generally similar among sites, except for docosahexaenoic acid (DHA), which was lower among stocked mussels relative to mussels maintained at the hatchery.Among the unrestored urban streams, the frequent occurrence of high discharge events resulted in burial and downstream loss of enclosures. At restored urban streams and rural streams, the washout effects were less severe. Apart from washout effects, mortality, as indicated by the presence of dead mussels, was low (<10%).Overall, rural and restored urban streams provided suitable conditions for stocking native mussels, whereas in unrestored urban streams, bed and bank instability during high discharge events resulted in a high attrition of mussels. Conservation efforts may be aided by the consideration of mussel habitat needs in the design of stream restoration projects. The inclusion of mussel stocking efforts in urban stream restoration projects has the potential to facilitate stream recovery, expand and bring greater attention to mussel conservation efforts, and garner public support for the preservation of stream health in urban areas. [ABSTRACT FROM AUTHOR]

The alleviation of landslide impacts is a priority since they have the potential to cause significant economic damage as well as the loss of human life. Mitigation can be achieved effectively by using warning systems and preventive measures. The development of improved methodologies for the analysis and understanding of landslides is at the forefront of this scientific field. Identifying effective monitoring techniques (accurate, fast, and low cost) is the pursued objective. Geographic Information Systems (GISs) and remote sensing techniques are utilized in order to achieve this goal. In this study, four methodological approaches (manual landslide delineation, a segmentation process, and two mapping models, specifically object-based image analysis and pixel-based image analysis (OBIA and PBIA)) were proposed and tested with the use of Unmanned Aerial Vehicles (UAVs) and data analysis methods to showcase the state and evolution of landslides. The digital surface model (DSM)-based classification approach was also used to support the aforementioned approaches. This study focused on streamside landslides at research sites in three different countries: Greece, Romania, and Turkey. The results highlight that the areas of the OBIA-based classifications were the most similar (98%) to our control (manual) classifications for all three sites. The landslides' perimeters at the Lefkothea and Chirlesti sites showed similar results to the OBIA-based classification (93%), as opposed to the Sirtoba site, where the perimeters of the landslides from OBIA-based classification were not well corroborated by the perimeters in the manual classification. Deposition areas that extend beyond the trees were revealed by the DSM-based classification. The results are encouraging because the methodology can be used to monitor landslide evolution with accuracy and high performance in different regions. Specifically, terrains that are difficult to access can be surveyed by UAVs because of their ability to take aerial images. The obtained results provide a framework for the unitary analysis of landslides using modern techniques and tools. [ABSTRACT FROM AUTHOR]

High-mountain ecosystems are experiencing acute effects of climate change, most visibly through glacier recession and the greening of the terrestrial environment. The streams draining these landscapes are affected by these shifts, integrating hydrologic, geologic, and biological signals across the catchment. We examined the organic and inorganic carbon dynamics of streams in four Alpine catchments in Switzerland to assess how glacier loss and vegetation expansion are affecting the carbon cycle of these high mountain ecosystems. We find that organic carbon concentration and fluorescence properties associated with humic-like compounds increase with vegetation cover within a catchment, demonstrating the increasing importance of allochthonous carbon sources following glacier retreat. Meanwhile, streams transitioned from carbon dioxide sinks to sources with decreasing glacier coverage and increased vegetation coverage, with chemical weathering and soil respiration likely determining the balance. Periods of sink behavior were also observed in non-glaciated streams, indicating geochemical consumption of carbon dioxide may be more common in high-mountain, minimally vegetated catchments than previously described. Together, these results demonstrate the dramatic shifts in carbon dynamics of alpine streams following glacier recession, with significant changes to both the organic and inorganic carbon cycles. The clear link between the terrestrial and aquatic zones further emphasizes the coupled dynamics with which all hydrologic and biogeochemical changes in these ecosystems should be considered, including the role of mountain streams in the global carbon cycle. [ABSTRACT FROM AUTHOR]

Benin's waterways are affected by several forms of pollution that are linked in particular to anthropic activities. This study aims to detect the presence of antibiotic residues, the frequency of antibiotic resistant bacteria and the levels of heavy metals in Benin's waterways. 160 surface water samples from streams in Benin were collected. They were filtered by the membrane filtration method, then incubated on different media. The isolated bacterial species were identified by API 20E gallery and specific biochemical tests. After detection of the resistance profile of the latter, the antibiotic residues were quantified in the samples by the ELISA technique on plate and the physicochemical analyses were performed by Multi 3630 IDS SET KS2 multimeter. Finally, heavy metal levels were detected by the MERCK test kit method specific to each metal. The bacterial species mostly identified were Klebsiella pneumoniae (56.59%), Klebsiella spp. (18.68%), Enterobacter spp. (12.63%). The most abundant resistance of bacterial strains was to amoxicillin + clavulanic acid (92%), followed by metronidazole (86%). Metronidazole was the antibiotic with the highest residue concentration in the samples (6.578 to 6.829 µg/L), followed by ciprofloxacin (2.142 to 9.299 µg/L). Benin streams contain heavy metals such as mercury (0.454±0.129 µg/L), lead (0.040±0.50 mg/L), zinc (6.120±16.017 mg/L), nickel (0.155±0.233 mg/L) and cadmium (0.154±0.132 mg/L). The analysis of the physico-chemical parameters showed that, apart from electrical conductivity, all parameters comply with Beninese and World Health Organization standards. Actions must be taken to clean up these rivers to preserve the integrity of aquatic ecosystems in Benin. [ABSTRACT FROM AUTHOR]

Rivers suffer from multiple stressors acting simultaneously on their biota, but the consequences are poorly quantified at the global scale. We evaluated the biological condition of rivers globally, including the largest proportion of countries from the Global South published to date. We gathered macroinvertebrate‐ and fish‐based assessments from 72,275 and 37,676 sites, respectively, from 64 study regions across six continents and 45 nations. Because assessments were based on differing methods, different systems were consolidated into a 3‐class system: Good, Impaired, or Severely Impaired, following common guidelines. The proportion of sites in each class by study area was calculated and each region was assigned a Köppen‐Geiger climate type, Human Footprint score (addressing landscape alterations), Human Development Index (HDI) score (addressing social welfare), % rivers with good ambient water quality, % protected freshwater key biodiversity areas; and % of forest area net change rate. We found that 50% of macroinvertebrate sites and 42% of fish sites were in Good condition, whereas 21% and 29% were Severely Impaired, respectively. The poorest biological conditions occurred in Arid and Equatorial climates and the best conditions occurred in Snow climates. Severely Impaired conditions were associated (Pearson correlation coefficient) with higher HDI scores, poorer physico‐chemical water quality, and lower proportions of protected freshwater areas. Good biological conditions were associated with good water quality and increased forested areas. It is essential to implement statutory bioassessment programs in Asian, African, and South American countries, and continue them in Oceania, Europe, and North America. There is a need to invest in assessments based on fish, as there is less information globally and fish were strong indicators of degradation. Our study highlights a need to increase the extent and number of protected river catchments, preserve and restore natural forested areas in the catchments, treat wastewater discharges, and improve river connectivity. [ABSTRACT FROM AUTHOR]

Despite the reported allelopathic nature of the Eucalyptus genus, eucalypt leachates have unknown effects on the trophic base of stream green food webs. Eucalypt plantations have increased worldwide, including riparian ecosystems. We aimed to test whether short-term eucalypt leachates might alter water chemistry, periphytic algal biomass and diatoms, and herbivorous invertebrates' (i.e., scrapers). We studied two oligotrophic and well-preserved headwaters from NW Spain. The experiment followed a before-after control-impact paired (BACIp) design, with weekly sampling before and after eucalypt leaves addition to streams. In the stream with lower discharge, the eucalypt treatments seemed to affect increases in biomass accrual (Chl-a) and diatom assemblages, disfavouring sensitive species (e.g., Eunotia minor and Achnanthidium pyrenaicum). Therefore, the ecological status was reduced from high to good. In the stream with higher discharge, invertebrate assemblages changed with scrapers having their abundances modified in comparison with the control (e.g., Habrophlebia sp. and Elmidae). Results suggest that eucalypt leaves leachates exert toxic effects on periphyton and on diatom and invertebrate assemblages, and this effect might be mediated by discharge. Alterations at the base of stream food webs may compromise their good ecological status. Further studies are necessary to identify whether this toxicity is due to allelopathic processes. [ABSTRACT FROM AUTHOR]

In 2009, Hancock, Pattinson and Ghani gave a coalgebraic characterisation of stream processors AN → BN drawing on ideas of Brouwerian constructivism. Their stream processors have an intensional character; in this paper, we give a corresponding coalgebraic characterisation of extensional stream processors, i.e., the set of continuous functions AN → BN. Our account sites both our result and that of op. cit. within the apparatus of comodels for algebraic effects originating with Power-Shkaravska. Within this apparatus, the distinction between intensional and extensional equivalence for stream processors arises in the same way as the the distinction between bisimulation and trace equivalence for labelled transition systems and probabilistic generative systems. [ABSTRACT FROM AUTHOR]

The aquatic, invasive New Zealand mud snail (Potamopyrgus antipodarum) exploits a variety of food sources. Here we examine the change in growth of snails that fed on periphyton colonizing leaf litter, wood, rock, and a control. Juveniles were grown in the lab on Spirulina algae powder (control) or periphyton grown on rock, leaf litter, or wood. Length was measured at the beginning of the experiment and after eight weeks. Snails grown on leaf litter increased in length more than twice as much as the control and the snails in the rock treatment, and the snails grown on wood showed an increase in length more than twice as much as snails in the rock treatment. This suggests that allochthonous material may contribute to a more nutritious food source for New Zealand mud snails and possibly aid in their invasion success. [ABSTRACT FROM AUTHOR]

• >20,000 groundwater-surface water (GW-SW) interaction papers published (1970–2023). • GW-SW interactions research is expanding beyond the hydrological sciences. • Future research should look to upscale site-specific findings to inform management. Interactions between groundwater and surface water sustain groundwater-dependent ecosystems and regulate river temperature and biogeochemical cycles, amongst many other processes. These interactions occur in freshwater environments including rivers, springs, lakes, and wetlands, and in coastal environments via tidal pumping, submarine groundwater discharge, and seawater intrusion. Here, we explore groundwater-surface water interactions research using bibliometric analyses of titles, abstracts, and keywords from 20,275 journal papers published between 1970 and 2023 extracted from Scopus. Analyses show that research into groundwater-surface water interactions is highly multi-disciplinary, with growing contributions from the social and biological sciences. The number of groundwater-surface water interactions papers is rapidly increasing with over 1200 papers published per year since 2020. Drawing on our data-driven approach and expert knowledge, we synthesise current research trends and identify critical future research directions. Despite the thousands of papers on groundwater-surface water interactions, important processes are still difficult to quantify or predict at meaningful spatial scales to inform water-resources management. We see benefits in future groundwater-surface water interactions research focusing on: (1) using new technologies including internet-of-things-based sensors, uncrewed vehicles, and remote-sensing approaches for data collection to inform groundwater-surface water interactions at large scales, (2) seeking approaches to upscale site-specific findings to better inform management, and (3) continuing the movement towards multi-disciplinary investigations to better inform the understanding of groundwater-surface water interactions and processes that will enable better management outcomes. [ABSTRACT FROM AUTHOR]

β-diversity is often measured over both spatial and temporal gradients of elevation, latitude, and environmental conditions. It is of particular interest to ecologists, as it provides opportunities to test and infer potential causal mechanisms determining local species assemblages. However, studies of invertebrate β-diversity, especially aquatic insects, have lagged far behind other biota. Using partial Mantel tests, we explored the associations between β-diversity of insects found in the coastal streams of Alabama, USA, and stream conditions and distances among sites. β-diversity was expressed using the Sørensen index, βSor, stream conditions were expressed as principal components (PCs), and distances as Euclidean distances (km) among sites. We also investigated the impact of seasonality (fall, summer) and taxonomic resolution (genus, species) on βSor. Regardless of season, βSor was significantly correlated (p < 0.01; r > 0.44) with stream conditions (stream size and water chemistry), while taxonomic resolution had minimal effect on associations between βSor and stream conditions. Distance was never correlated with changes in βSor (p > 0.05). We extended the use of the Sørensen pair-wise index to a multiple-site dissimilarity, βMult, which was partitioned into patterns of spatial turnover (βTurn) and nestedness (βNest). Changes in βMult were driven mostly by turnover rather than nestedness.

Mountaintop removal coal mining (MTR) has been a major source of landscape change in the Central Appalachians of the United States (US). Changes in stream hydrology, channel geomorphology and water quality caused by MTR coal mining can lead to severe impairment of stream ecological integrity. The objective of the Clean Water Act (CWA) is to restore and maintain the ecological integrity of the Nation's waters. Sensitive, readily measured indicators of ecosystem structure and function are needed for the assessment of stream ecological integrity. Most CWA assessments rely on structural indicators; inclusion of functional indicators could make these assessments more holistic and effective. The goals of this study were: (1) test the efficacy of selected carbon (C) and nitrogen (N) cycling and microbial structural and functional indicators for assessing MTR coal mining impacts on streams; (2) determine whether indicators respond to impacts in a predictable manner; and (3) determine if functional indicators are less likely to change than are structural indicators in response to stressors associated with MTR coal mining. The structural indicators are water quality and sediment organic matter concentrations, and the functional indicators relate to microbial activity and biofilm production. Seasonal measurements were conducted over the course of a year in streams draining small MTR-impacted and forested watersheds in the Twentymile Creek watershed of West Virginia (WV). Five of the eight structural parameters measured had significant responses, with all means greater in the MTR-impacted streams than in the forested streams. These responses resulted from changes in source or augmentation of the original source of the C and N structural parameters because of MTR coal mining. Nitrate concentration and the stable carbon isotopic ratio of dissolved inorganic carbon were the most effective indicators evaluated in this study. Only three of the fourteen functional indicators measured had significant responses to MTR coal mining, with all means greater in the forested streams than in the MTR-impacted streams. These results suggest that stressors associated with MTR coal mining caused reduction in some aspects of microbial cycling, but resource subsidies may have counterbalanced some of the inhibition leading to no observable change in most of the functional indicators. The detritus base, which is thought to confer functional stability, was likely sustained in the MTR-impacted streams by channel storage and/or leaf litter inputs from their largely intact riparian zones. Overall, our results largely support the hypothesis that certain functional processes are more resistant to stress induced change than structural properties but also suggest the difficulty of identifying suitable functional indicators for ecological integrity assessment.

New experimental techniques are allowing, for the first time, direct visualization of mass and momentum transport across the sediment-water interface in streams. These experimental insights are catalyzing a renaissance in our understanding of the role stream turbulence plays in a host of critical ecosystem services, including nutrient cycling. In this commentary, we briefly review the nature of stream turbulence and its role in hyporheic exchange and nutrient cycling in streams. A simple process-based model, borrowed from biochemical engineering, provides the link between empirical relationships for grain-scale turbulent mixing and nutrient processing at reach, catchment, continental, and global scales.

Agriculture, the world's most dominant land use type, burdens freshwater biodiversity with a multitude of stressors such as diffuse pollution and hydromorphological alteration. However, it is difficult to directly link agricultural land use with biota response as agricultural stressors can also originate from other causes. Also, there is evidence for positive and negative effects of agriculture on organisms, agricultural impact differs strongly with the biological metric and study region considered and agricultural impact differs among practice and type, which in turn affects different organism groups with varying severity. Against this background, our study aimed at assessing, if agricultural land use has a consistent effect on river biota. We conducted a systematic review of the literature, which yielded 43 studies and 76 relationships between agriculture and aquatic organism groups. The relationships were subjected to a meta-analysis using Hedge's g to calculate the standardized mean difference of effects. Overall, we detected a medium to strong effect g = − 0.74 of agricultural land use on freshwater biota, only marginally influenced by study design, river type and region. Strong differences in biota response could be observed depending on the biological metric assessed, with ecological quality indices of agricultural impairment performing best. Sensitive taxa declined with agricultural impact, while tolerant taxa tended to benefit. In addition, the biota response differed among agricultural types and practices and organism group, with macroinvertebrates showing the strongest effect. Our results quantify the effects of agriculture on riverine biota and suggest biological metric types for assessing agricultural impact. Further research is needed to discriminate between agricultural types and account for intensity. [ABSTRACT FROM AUTHOR]

European ecosystems have been subject to extensive shifts in anthropogenic disturbance, primarily through atmospheric deposition, climate change, and land management. These changes have altered the macronutrient composition of aquatic systems, with widespread increases in organic carbon (C), and declines in nitrogen (N) and phosphorus (P). Less well known is how these disturbances have affected nutrient stoichiometry, which may be a more useful metric to evaluate the health of aquatic ecosystems than individual nutrient concentrations. The Swedish west coast has historically experienced moderate to high levels of atmospheric deposition of sulfate and N, and eutrophication. In addition, coastal waters have been darkening with damaging effects on marine flora and fauna. Here, we present three decades of macronutrient data from twenty lakes and watercourses along the Swedish west coast, extending from headwaters to river mouths, across a range of land covers, and with catchments ranging 0.037–40,000 km2. We find a high degree of consistency between these diverse sites, with widespread increasing trends in organic C, and declines in inorganic N and total P. These trends in individual macronutrients translate into large stoichiometric changes, with a doubling in C:P, and increases in C:N and N:P by 50% and 30%, showing that freshwaters are moving further away from the Redfield Ratio, and becoming even more C rich, and depleted in N and P. Although recovery from atmospheric deposition is linked to some of these changes, land cover also appears to have an effect; lakes buffer against C increases, and decreases in inorganic N have been greatest under arable land cover. Our analysis also detects coherently declining P concentrations in small forest lakes; so called (and unexplained) "oligotrophication." Taken together, our findings show that freshwater macronutrient concentrations and stoichiometry have undergone substantial shifts during the last three decades, and these shifts can potentially explain some of the detrimental changes that adjacent coastal ecosystems are undergoing. Our findings are relevant for all European and North American waters that have experienced historically high levels of atmospheric deposition, and provide a starting point for understanding and mitigating against the trajectories of long-term change in aquatic systems. [ABSTRACT FROM AUTHOR]

Aim: The species–area relationship (SAR) is one of the most distinctive biogeographic patterns, but global comparisons of the SARs between island and mainland are lacking for microbial taxa. Here, we explore whether the form of the SAR and the drivers of species richness, including area, environmental heterogeneity, climate and physico‐chemistry, differ between islands and similarly sized areas on mainland, referred to as continental area equivalents (CAEs). Location: Global. Taxon: Stream benthic diatoms. Methods: We generated CAEs on six continental datasets and examined the SARs of CAEs and islands (ISAR). Then, we compared CAEs and islands in terms of total richness and richness of different ecological guilds. We tested the factors contributing to richness in islands and CAEs with regressions. We used structural equation models to determine the effects of area versus environmental heterogeneity, climate and local conditions on species richness. Results: We found a non‐significant ISAR, but a significant positive SAR in CAEs. Richness in islands was related to productivity. Richness in CAEs was mainly dependent on area and climate, but not directly on environmental heterogeneity. Species richness within guilds exhibited inconsistent relationships with island isolation and area. Main conclusions: Ecological and evolutionary processes shaping diatom island biogeography do not depend on area at the worldwide scale probably due to the presence of distinct species pool across islands. Conversely, area was an important driver of diatom richness in continents, and this effect could be attributed to dispersal. Continents had greater richness than islands, but this was a consequence of differences in environmental conditions such as specific island climatic conditions. We stress the need for more island data on benthic diatoms, particularly from archipelagos, to better understand the biogeography of this most speciose group of algae. [ABSTRACT FROM AUTHOR]

One of the risks faced by habitat restoration practitioners is whether habitats included in restoration planning will be used by the target species or, conversely, whether habitats excluded from restoration planning would have benefited the target species. With the goal of providing a quantitative decision‐making approach that represented varying levels of risk tolerance, we used multiple probability decision thresholds (PDT) to predict the range of occurrence for three anadromous fishes (Oncorhynchus spp.) in a watershed in southwestern Washington, USA. For each species, we compared the predicted range of occurrence to the distribution used for restoration planning and quantified the amount of habitat blocked by anthropogenic barriers. Coho salmon (O. kisutch) had the broadest predicted range of occurrence (3061.6–6357.9 km; 0.75–0.25 PDT), followed by steelhead trout (O. mykiss; 1828.8–2836.8 km) and chum salmon (O. keta; 1373.9–1629.1 km). For each species, the predicted range of occurrence was similar or greater than the distribution used for restoration planning, suggesting that the current plan may exclude habitats that would benefit each species. Coho salmon had the greatest percentage of habitat blocked by anthropogenic barriers, followed by steelhead trout and chum salmon, respectively. Modeling species distributions at multiple risk‐tolerance scenarios acknowledges uncertainty in restoration planning and allows practitioners to weigh the ecological benefits and budgetary constraints when considering locations for restoration. To effectively communicate restoration science to support practitioners in decision‐making, we developed an R Shiny application online user interface available at: https://shiny.wdfw-fish.us/ChehalisRiverBasinSalmonidRangeOfOccurence/. [ABSTRACT FROM AUTHOR]

Maintaining regional‐scale freshwater connectivity is challenging due to the dendritic, easily fragmented structure of freshwater networks, but is essential for promoting ecological resilience under climate change. Although the importance of stream network connectivity has been recognized, lake‐stream network connectivity has largely been ignored. Furthermore, protected areas are generally not designed to maintain or encompass entire freshwater networks. We applied a coarse‐filter approach to identify potential freshwater corridors for diverse taxa by calculating connectivity scores for 385 lake‐stream networks across the conterminous United States based on network size, structure, resistance to fragmentation, and dam prevalence. We also identified 2080 disproportionately important lakes for maintaining intact networks (i.e., hubs; 2% of all network lakes) and analyzed the protection status of hubs and potential freshwater corridors. Just 3% of networks received high connectivity scores based on their large size and structure (medians of 1303 lakes, 498.6 km north–south stream distance), but these also contained a median of 454 dams. In contrast, undammed networks (17% of networks) were considerably smaller (medians of six lakes, 7.2 km north–south stream distance), indicating that the functional connectivity of the largest potential freshwater corridors in the conterminous United States currently may be diminished compared with smaller, undammed networks. Network lakes and hubs were protected at similar rates nationally across different levels of protection (8%–18% and 6%–20%, respectively), but were generally more protected in the western United States. Our results indicate that conterminous United States protection of major freshwater corridors and the hubs that maintain them generally fell short of the international conservation goal of protecting an ecologically representative, well‐connected set of fresh waters (≥17%) by 2020 (Aichi Target 11). Conservation planning efforts might consider focusing on restoring natural hydrologic connectivity at or near hubs, particularly in larger networks, less protected, or biodiverse regions, to support freshwater biodiversity conservation under climate change. [ABSTRACT FROM AUTHOR]

As a beneficial use of reclaimed water, the brackish wetland effluent serves as a water source for estuarine wetland restoration projects and brackish surface waters while sustaining natural ecosystems. This included aeration of subsurface-flow horizontal wetlands to support the microbial conversion of ammonium to nitrate and subsequently to gaseous nitrogen in the anaerobic second-stage wetlands (Photo 2). Keywords: Discharge; Concentrate Management; Reverse Osmosis; Water Quality; State Regulations; Federal Regulations; Compliance; Wetlands; Desalination; Contaminants; Wastes; Surface Water; Brines; Dilution; Environment; Water Resources; Membranes; Industrial Wastes; Metals; Nutrients; Standards; Streams; Utilities; Costs; Pipes; Aeration; pH; Disinfection; Dechlorination EN Discharge Concentrate Management Reverse Osmosis Water Quality State Regulations Federal Regulations Compliance Wetlands Desalination Contaminants Wastes Surface Water Brines Dilution Environment Water Resources Membranes Industrial Wastes Metals Nutrients Standards Streams Utilities Costs Pipes Aeration pH Disinfection Dechlorination 79 82 4 11/03/22 20221101 NES 221101 GLO:KNS/01nov22:awwa2002-gra-0001.jpg PHOTO (COLOR): . gl The City of Oxnard's Advanced Wastewater Purification Plant demonstrated the treatment potential of reverse osmosis concentrate management using constructed wetlands. [Extracted from the article]

Freshwater ecosystems are globally significant sources of greenhouse gases (GHGs) to the atmosphere. Previous work has indicated that GHG flux in headwater streams is dominated by terrestrially derived gases, with in situ production limited by short organic matter residence times and high dissolved oxygen concentrations due to turbulent reaeration. However, low‐gradient headwater streams that contain pool structures with longer residence times may be conducive to the in situ production of GHG. These streams, and the longitudinal heterogeneity therein, are seldom studied. We measured continuous ecosystem metabolism alongside concentrations and fluxes of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) in a low‐gradient third order stream in the North Carolina Piedmont. From autumn to the following spring, we characterized spatial and temporal patterns of GHG along an 8 km segment in the context of channel geomorphology, hydrology, and ecosystem metabolic rates using linear mixed effects models. We found that stream metabolism was responsible for most of the CO2 flux over this period, and that in‐channel aerobic metabolism was a primary predictor of both CH4 and N2O fluxes as well. Long water residence times, limited reaeration, and substantial organic matter from terrestrial inputs foster conditions conducive to the in‐stream accumulation of CO2 and CH4 from microbial respiration. Streams like this one are common in landscapes with low topographic relief, making it likely that the high contribution of instream metabolism to GHG fluxes that we observed is a widespread yet understudied behavior of many small streams. Plain Language Summary: Stream ecosystems play a role in producing greenhouse gases (GHGs) and transporting them from groundwater to be released into the atmosphere. Some of these gases are produced through the breakdown of organic matter by microbes in the stream. We don't know how important this microbial production is compared to gases coming from soil and groundwater, but comparing it to rates of ecosystem metabolism may help us learn about it. We measured GHG and metabolism along a stream and found that metabolism is directly responsible for the production of carbon dioxide and is a good predictor of methane, meaning that microbial production in the stream is likely important. N2O production was limited by competition between microbes for nitrogen, as a result, the stream was removing N2O from the atmosphere rather than releasing it. Key Points: Patterns in carbon dioxide are almost entirely accounted for by instream metabolism except during a storm eventMethane is highly variable in space and covaries with aerobic respirationThe stream shifts from a source of nitrous oxide to a sink during peak autumn respiration, likely due to nitrogen limitation [ABSTRACT FROM AUTHOR]

Species conservation often faces many challenges, such as addressing threats from multiple stressor sources, representing under-studied taxa, and understanding implications of spatial extent. To overcome these challenges, we assessed contemporary anthropogenic threats from stream fragmentation and landscape disturbance as well as future habitat suitability under climate change for traditionally well-studied (fishes) and under-studied (mussels) imperiled fluvial taxa in Michigan, USA. To understand how threats to species vary spatially, predicted habitat suitability was analyzed for three hierarchically nested spatial extents: statewide, within species' biogeographic ranges, and within river patches fragmented by barriers. Comparison of current and future habitat suitability for 27 fish and 23 mussel species indicates large potential statewide gains for many warmwater and/or large river fishes and several mussel species, however these gains are greatly diminished by biogeographic range limitations and habitat fragmentation among current and future habitats. One mussel species and several cold- and coolwater fishes are projected to have significant habitat losses under climate change irrespective of spatial extent. On average, 79% of habitats for mussels and 58% for fishes were considered moderately to severely disturbed from current human landscape activities. Habitat fragmentation was greater for fishes than mussels, with large dams playing a primary role in fragmenting habitats relative to small dams and waterfalls. Results indicate that threat assessments can vary substantially according to spatial extent and taxa, and consideration of both contemporary and future threats to habitats is needed to inform conservation of imperiled fluvial organisms. [ABSTRACT FROM AUTHOR]

The genus Harttia belongs to the subfamily Loricariinae and has to date 27 described species, distributed in the drainages of Guiana Shield, Amazon and southeastern Brazil. The new species is distinguished from its congeners by the combination of: canal plate present; abdominal plates absent; trapezoid preanal plates; males with elongated and conspicuous odontodes on the first pectoral-fin ray and on the lateral region of the head, close to the canal plate; and dorsal-fin spinelet present. An identification key for the species of the rio São Francisco basin and a comparison between the new taxon and all other species of the genus are presented. [ABSTRACT FROM AUTHOR]

The majority of dams in the contiguous United States are small, low-head dams that are no longer operational but can influence the water quality of contemporary stream ecosystems. Potential effects of low-head dams on stream nitrogen removal (denitrification) have been rarely quantified, and yet they can be an important part of the decision-making process of removing low-head dams. Here, we provide novel empirical data on potential denitrification rates and their biogeochemical controls above and below two mid-Atlantic low-head dams over a 2-year period. Our results show that low-head dams did not increase streambed potential denitrification in comparison to dam-free sections in the same rivers. In our study sites, potential denitrification above low-head dams was generally low (15.7 ± 3.5 µg N [kg sediment]−1 h−1) despite recurring events of water hypoxia (< 50% dissolved oxygen saturation) and high NO3− and DOC concentrations. Overall, we observed higher potential denitrification during winter samplings (9.2 and 50.1 µg N [kg sediment]−1 h−1 on average) and significant effects of sediment surface area and organic matter content on potential denitrification rates above the dams. Results from this study suggest limited effects of relic low-head dams on nitrogen removal and transport in stream ecosystems, and can contribute to the decision-making process of removing low-head dams. [ABSTRACT FROM AUTHOR]

Specific features of the formation of the structure of bottom communities in rivers of esker landscapes with dissected topography are analyzed using original samples of macrozoobenthos, and 110 invertebrate taxa are identified. It is shown that the species composition of the macrozoobenthos in rivers on the northern coast of Lake Onega is formed under the effect of the poor regional fauna of Eastern Fennoscandia. The dissected topography is a local factor of the formation of a large number of open lakes in the river network and of many zones under the limnic effect. As a result, benthic communities are characterized by high abundance and biomass (10 000 ind./m2 and 52 g/m2 on average in rapids and 3000 ind./m2 and 12 g/m2 on average in pools, respectively). The portion of collector–filterers in the macrozoobenthos is large (43% of the total biomass on average in the zones of the lake effect), and they are capable of consuming the seston coming from lakes. [ABSTRACT FROM AUTHOR]