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Stocking can affect population density but may influence fish growth responses to changes in environmental conditions. In a multi‐year field experiment, we investigated the interactive effects of density and temperature on the growth of young‐of‐the‐year anadromous brown trout in streams stocked with wild‐origin hatchery‐reared brown trout. Fish origin was the predominant factor influencing growth rate, thereby highlighting the importance of discriminating between wild and hatchery‐reared individuals. Growth was positively related to temperature (degree‐days) and negatively related to density, with the growth response to temperature modulated by density. Temperature had a more pronounced effect on juvenile growth at low density than at high density. The reduced growth response to temperature caused by density could reduce population resilience and should be considered in management and conservation strategies. [ABSTRACT FROM AUTHOR]

High mountain freshwater systems are particularly sensitive to the impacts of global warming and relevant environmental changes. Microorganisms contribute substantially to biogeochemical processes, yet their distribution patterns and driving mechanism in alpine streams remain understudied. Here, we examined the bacterial and fungal community compositions in stream biofilm along the elevational gradient of 745–1874 m on Mt. Kilimanjaro and explored their alpha and beta diversity patterns and the underlying environmental drivers. We found that the species richness and evenness monotonically increased towards higher elevations for bacteria, while were non-significant for fungi. However, both bacterial and fungal communities showed consistent elevational distance-decay relationships, i.e., the dissimilarity of assemblage composition increased with greater elevational differences. Bacterial alpha diversity patterns were mainly affected by chemical variables such as total nitrogen and phosphorus, while fungi were affected by physical variables such as riparian shading and stream width. Notably, climatic variables such as mean annual temperature strongly affected the elevational succession of bacterial and fungal community compositions. Our study is the first exploration of microbial biodiversity and their underlying driving mechanisms for stream ecosystems in tropical alpine regions. Our findings provide insights on the response patterns of tropical aquatic microbial community composition and diversity under climate change. [ABSTRACT FROM AUTHOR]

In recent decades, aquatic ecosystems have suffered a series of impacts that have made them some of the most threatened ecosystems on a global scale. So, protection measures are needed to conserve the biodiversity we find in some of the less impacted ecosystems. In the Spanish legislation, a category arose for this purpose in lotic ecosystems, the River Natural Reserve (RNR). In this work, we analyse the taxonomic and functional diversity of 145 macroinvertebrate biocoenoses from 128 different RNRs belonging to 10 different basins and representing 18 typologies. Most of the analysed biocoenoses have an overall high taxonomic diversity, with some exceptions corresponding to particular reaches suffering occasional disturbances or with very special conditions. An intermediate functional homogeneity has been also detected, related to a relatively low average functional richness. We also found medium levels of functional evenness, a high functional divergence, and low functional dispersion and Rao index values, the latter supporting similarities among taxa in functional terms. In our studied systems, there is high taxa turnover, but functional turnover is very low. This means that most of the trait dissimilarity between taxa is found within a community, but not among communities, though there are relatively strong dissimilarities in community composition. Our results support the fact that the RNRs are protecting communities of great diversity, not only taxonomic, but also functional, which contributes to the proper functioning of the ecosystems found in these stream reaches. Thus, the analysis of the functional diversity of the communities, as in the present approach, should be implemented to identify and prioritize protection of reaches with higher functional diversity, where enhanced ecosystem functioning can be expected. [ABSTRACT FROM AUTHOR]

Information on the riverbanks can improve our ability to monitor water quality and generate adequate management strategies. This research seeks insights into the riverbanks of eight Colastiné River Basin (Argentina) streams, which have been influenced by intensive agricultural land use for decades. We aim to (a) describe the temporal and spatial distribution patterns of riparian vegetation, (b) assess their current riparian quality through riverbank quality indices, and (c) estimate whether the riparian quality is linked to the water quality. Results of the Normalized Difference Vegetation Index (NDVI) showed an increasing trend in the vegetation cover with seasonal periodicities during the last 22 years in only 2 streams. Overall, 41% of plant species registered were exotic although native species dominated in most streams. The overall riverbank quality, based on the mean values of four riverbank quality indexes, was regular-to-bad. The overall water quality of the streams was low and significantly correlated to the Riparian Quality Index, suggesting a link between both compartments. More studies are needed to determine the main variables that establish this connection. Further effort is also needed to generate appropriate indices for this region, as no current ones are still developed. [ABSTRACT FROM AUTHOR]

Exploring nitrogen dynamics in stream networks is critical for understanding how these systems attenuate nutrient pollution while maintaining ecological productivity. We investigated Oak Creek, a dryland watershed in central Arizona, USA, to elucidate the relationship between terrestrial nitrate (NO3−) loading and stream NO3− uptake, highlighting the influence of land cover and hydrologic connectivity. We conducted four seasonal synoptic sampling campaigns along the 167‐km network combined with stream NO3− uptake experiments (in 370–710‐m reaches) and integrated the data in a mass‐balance model to scale in‐stream uptake and estimate NO3− loading from landscape to the stream network. Stream NO3− concentrations were low throughout the watershed (<5–236 μg N/L) and stream NO3− vertical uptake velocity was high (5.5–18.0 mm/min). During the summer dry (June), summer wet (September), and winter dry (November) seasons, the lower mainstem exhibited higher lateral NO3− loading (10–51 kg N km−2 d−1) than the headwaters and tributaries (<0.001–0.086 kg N km−2 d−1), likely owing to differences in irrigation infrastructure and near‐stream land cover. In contrast, during the winter wet season (February) lateral NO3− loads were higher in the intermittent headwaters and tributaries (0.008–0.479 kg N km−2 d−1), which had flowing surface water only in this season. Despite high lateral NO3− loading in some locations, in‐stream uptake removed >81% of NO3− before reaching the watershed outlet. Our findings highlight that high rates of in‐stream uptake maintain low nitrogen export at the network scale, even with high fluxes from the landscape and seasonal variation in hydrologic connectivity. Plain Language Summary: Exploring nitrogen dynamics in desert streams is critical for understanding how these systems can reduce pollution while maintaining healthy ecosystems. We examined how seasons and human activities, like farming and development, affect nitrogen pollution in a desert stream in Arizona, USA. We found that in seasons with little rain, nitrogen delivery to the stream was high in areas where irrigation is common. However, in‐stream nitrogen remained low because of the high capacity of the stream algal and microbial community to remove nitrogen from the water. This reveals that plants and microbes play a vital role in regulating nitrogen in deserts. This study has broad implications beyond this particular desert stream, emphasizing the importance of understanding complex interactions between human activities, water, and stream microbes. By studying these interactions, we can better manage and preserve desert streams with changing climate and human pressures. Key Points: Nitrate loading to a dryland stream network varies spatially and seasonally due to hydrologic connection to landscape nutrient sourcesHigh in‐stream nitrate uptake maintained low stream nitrate concentration and watershed export even when landscape inputs were highIn drylands, hydrologic disconnections in space and time between nitrate sources and the stream requires a flexible modeling approach [ABSTRACT FROM AUTHOR]

The relative influence of seasonal patterns in hydrological flow and seasonal differences in biological and geochemical activity on stream chemistry patterns is difficult to discern because they covary; temperate systems are characterized by lower mean flow in the summer (i.e. corresponding to deeper flow paths, elevated temperature, and biological activity), and higher mean flow in the winter (i.e. corresponding to shallower flow paths, depressed temperature, and biological dormancy). Using 2018 data, when seasonal stream flow conditions reversed, and two prior conventional water years, the relationship between monthly acid-relevant analyte concentrations and streamflow were compared within and between winter and summer to provide insight into controls on characteristic seasonal chemistry patterns at two mid-Appalachian sites with distinct geology (weatherable mafic and weather resistant siliciclastic). Acid neutralizing capacity (ANC) increased (1) with lower flow, in both seasons and (2) in summer, for all flow conditions. The compounding impacts resulted in a doubling of concentration from typical winter with high flow to summer with low flow at both sites. Base cation patterns tracked ANC at the mafic site, resulting in an ~ 60% increase of from winter with high flow to summer with low flow; distinctions between summer and winter contributed more to the seasonal pattern (72%) than changes in flow. Sulfate increased at the mafic site (1) with higher flow, in both seasons and (2) in winter, for all flow conditions, resulting in an ~ 50% increase from summer with low flow to winter with high flow; distinctions between winter and summer conditions and flow contributed similarly (40–60%) to the typical seasonal chemical pattern. The biogeochemical mechanism driving differences in stream chemistry between summer and winter for the same flow conditions is likely increased rates of natural acidification from elevated soil respiration in summer, resulting in greater bedrock weathering and sulfate adsorption. Findings highlight the significance and consistency of growing vs dormant season variations in temperature and biological activity in driving intra-annual patterns of stream solutes. This data set informs parameterization of hydro-biogeochemical models of stream chemistry in a changing climate at a biologically relevant, seasonal, timescale. [ABSTRACT FROM AUTHOR]

Elucidating the habitat-related processes driving variation in juvenile recruitment and population fluctuation is crucial for the conservation of freshwater fishes, particularly for species at risk, where recruitment variation increases at small population size. We used a combination of instream enclosure experiments and habitat use observations to investigate between-stream variation in recruitment of juvenile Nooksack Dace (Rhinichthys cataractae sp. cataractae), a federally endangered stream-dwelling minnow endemic to the lower Fraser Valley of British Columbia, Canada. There was no evidence for a recruitment bottleneck associated with high water temperature or low dissolved oxygen in spawning riffles at the egg incubation stage, or during a two week juvenile growth experiment in enclosures, although larval dace growth was positively related to temperature. However, immediately post-hatch dace showed a very strong preference for shallow (<5 cm deep), fine substrate marginal shoal habitat with no overhanging or instream vegetation cover, which was associated with well-developed pool-riffle channel structure. Shallow marginal rearing habitat was absent in the stream experiencing recruitment failure, where encroachment by invasive reed canarygrass (Phalaris arundinacea) created homogenous steep-bank habitat with heavy instream vegetation cover, implicating loss of critical marginal rearing habitat as the recruitment bottleneck. [ABSTRACT FROM AUTHOR]

Water column removal in streams is a nitrogen (N) cycling pathway that has been historically overlooked. Studies filling this knowledge gap have focused on the role of water column N removal in mid‐to‐large‐order rivers with consistently high suspended sediment concentrations. However, smaller streams may provide comparable suspended sediment concentrations during and after storm events, creating favorable conditions for water column N removal. To assess the presence, magnitude, and control of water column N removal during storms in low‐order watersheds, we measured water column denitrification and heterotrophic assimilatory N uptake rates at three locations in a Mid‐Atlantic watershed during five storm events of different magnitude, sediment loads, and nutrient availability. We found large variations in water column denitrification (0–5.56 mg N g−1 d−1) and assimilatory uptake (0.003–1.67 mg N g−1 d−1). Higher rates of N removal occurred during flow recession, with a correlation between suspended sediment organic matter content and denitrification. On average, denitrification rates in the water column were higher when flashy responses to storm events occurred. In contrast to denitrification, water column N removal rates (as both denitrification and heterotrophic assimilation) during storm events were comparable to those measured at baseflow in larger rivers. However, water column denitrification could only account for less than 10% of potential reach‐scale N removal during most of the storm events. Our findings provide insight into the ecological relevance of small stream water columns and suggest that more research is needed to understand the magnitude of stream water column processing on watershed‐scale N removal. Plain Language Summary: In freshwater ecosystems, microorganisms facilitate the transfer of nutrients from the surrounding environment to other organisms. Through a process known as nitrogen removal, microbes capture and modify nitrogen—an essential element for life—into forms that other organisms can use. In streams, microbes that perform nitrogen removal can live on the streambed, or on the surface of small sediment particles suspended in the water column. During storms, the amount of suspended particles in a stream increases dramatically, potentially providing more surface area where nitrogen removal can occur. Our study measured how much nitrogen removal takes place in the water column of streams during storms. We also determined whether other environmental factors influence the rates of removal. We found that higher rates of nitrogen removal occur after the peak of a storm, when the stream water level is decreasing. Additionally, we found that the rate of nitrogen removal increases with the amount of organic matter present in the suspended sediment. Overall, the rates of uptake we measured were comparable to those observed in much larger rivers, suggesting that nitrogen uptake in the water column during storms may be an important but overlooked component of the nitrogen cycle in small streams. Key Points: More flashy storms showed higher rates of water column denitrificationWater column removal rates were higher during flow recession than during rising flowsDenitrification was positively related to organic matter content in suspended sediment, whereas N uptake decreased with suspended chlorophyll [ABSTRACT FROM AUTHOR]

New material of water mites (Acari: Hydrachnidia) from the Uttarakhand State of India is reported. One species, Sperchon dobriyali n. sp., is described as new for science. The male is for the first time described for Sperchonopsis himalayaensis Pešić, Smit, Sharma, Rana, Bahuguna & Rayal, 2022, and the female is for the first time described for Aturus uttarakhandensis Pešić, Smit, Sharma, Rana, Bahuguna & Rayal, 2022.https://zoobank.org/urn:lsid:zoobank.org:pub:47F0603A-1552-488C-8F31-AF2714B45132 [ABSTRACT FROM AUTHOR]

Basal resource quality can have strong bottom-up effects on consumer taxonomic and functional diversity, particularly at smaller spatial scales within an ecoregion. However, these effects may be attenuated at broader scales among ecoregions and in more environmentally dynamic systems where abiotic constraints may exert stronger controls on consumer diversity. To examine broader-scale functional diversity responses among ecoregions to varying elemental and hydrological environments, we investigated the relationship between functional diversity of benthic macroinvertebrate communities, periphyton resource stoichiometry, and flow regime. We used data from 27 lotic sites managed by the National Ecological Observatory Network over a 4-y period between 2016 and 2019. Contrary to our predictions, periphyton C∶P ratio was not a strong predictor of variation in functional diversity among these streams. However, invertebrate density decreased with increased algal C∶P, suggesting that increased resource P availability can support higher consumer abundance. In contrast to periphyton stoichiometry, infrequent high-magnitude flows (indicated by short-term hydrograph skewness) predicted functional richness, and long-term high flow unpredictability was a predictor of all metrics of functional diversity. Specifically, hydrologically unpredictable sites had low functional diversity and were dominated by functional trait states like small body size, fast seasonal development, and univoltinism. These results indicate that across a broad gradient of environmental predictability, aspects of flow regime can constrain insect life histories and have greater impact than basal resource stoichiometry on functional trait diversity. Our finding that aquatic invertebrate functional and taxonomic diversity are constrained by flow variation at a continental scale advances our understanding of how human-dominated hydrologic regimes may further influence broad-scale patterns of community structure. [ABSTRACT FROM AUTHOR]

Based on the habitat types, thirty species of cyprinids in nine streams located in the Western Ghat mountain ranges, hotspot of biodiversity have been classified into six guilds. Shallow pools (<60cm deep and velocities <30 cm/s) were preferred by juveniles and adults of big sized barbs such as Hypselobarbus micropogon, Tor khudree and Neolissochilus wynaadensis. Slow riffles (< 60 cm deep and velocities 30-59 cm/s) were preferredby juveniles of surface dwellers such as Barilius canarensis, B. gatensis, Devario aequipinnatus, Salmophasia boopis, Salmophasia acinaces and Chela labuca; bottom and substrate dwellers such as Garramullya and Garra stenorhynchus. Fast riffles (< 60 cm deep and velocities ≥ 60 cm/s) were preferred by the surface dwelling species and species of Garra. Almost all the cyprinid species preferred the medium pool (60-149 cmdeep and velocities <30 cm/s). Big sized barbs and torines (game fish) were confined to deep pools (≥150 cm deep). Among the nine streams raceway is identified in one stream (60-149cm deep and velocities ≥30 cm/s) which was preferred by juveniles and adults of Garra stenorhynchus and Barilius gatensis. Guild structures ofcyprinid species are consistent in almost all the streams. [ABSTRACT FROM AUTHOR]

The results of long-term studies of the conjugate distribution of methane (CH4) and sulfide sulfur (Ssulfide) concentrations in the bottom sediments of watercourses of the steppe zone of the European part of Russia are analyzed. In addition to CH4 and Ssulfide, Eh and pH values, humidity and density were determined in different sediment horizons; CH4, dry residue, and pH values were determined in water. Concentrations of CH4 in the watercourses vary from <0.1 to 2007.0 μL/L (median 24.3 μL/L), with the largest number of values (72%) in the range 10.1–100.0 μL/L. The concentrations of CH4 and Ssulfide in the bottom sediments of watercourses are quite high and vary, respectively, from <0.01 to 51.0 µg/g of wet sediment (median 1.35 µg/g) and from <0.001 to 4.50 mg/g of wet sediment (median 0.813 mg/g). Usually, the CH4 and Ssulfide concentrations increase from the surface layer to the subsurface horizons, and then decrease. The difference between the distributions of Ssulfide and CH4 is the more frequent occurrence of maximum concentrations of Ssulfide in less deep sediment horizons. Seasonal changes were recorded in the vertical distribution of CH4 and Ssulfide not only in terms of their concentrations, but also in the position of maximum and minimum values. There is a weak positive correlation between the concentrations of CH4 and Ssulfide, which indicates the synchronous formation of these gases in separate layers of sediments of the studied watercourses. The positive correlation established between the CH4 concentrations in water and 0–2 cm layer of bottom sediments indicates that the sediments are an important source of CH4 in water and its emission into the atmosphere. [ABSTRACT FROM AUTHOR]

This study aims to evaluate the efficiency of electric fishing and seine-net/dip-net to obtain quantitative and qualitative data on the fish community of low conductivity streams in the semi-arid region of Bahia, Brazil. Samplings were collected in 15 streams in the region of Chapada Diamantina. Two homogeneous stretches with 50 m each were selected and closed with blocking nets. Zippin analysis was used to evaluate the suitability of each capture method. Differences in abundance, richness, composition of species, and length of specimens captured were compared for each method. Twenty-nine species were collected, twenty-four using electric fishing, and twenty-one using seine-net/dip-net. There were no significant differences between methods as for abundance, richness, composition of species, and length of the individual captured. There were no significant differences in capturability. Both methods have high values of sample efficiency (SE). Therefore, electric fishing and seine-net/dip-net are equally effective on describing qualitatively and quantitatively the fish community. It is noteworthy that for an ideal choice of collection method, the geomorphological characteristics of the streams must be taken into account since they exert a direct influence on both collection methods. [ABSTRACT FROM AUTHOR]

Streams are important sources of methane (CH4) to the atmosphere but magnitudes and regulation of stream CH4 fluxes remain uncertain. Stream CH4 can come from groundwater and/or produced in anoxic sediments. A fraction can be microbially oxidized to carbon dioxide (CO2) when passing redox gradients in soil, sediment, or water, while the fraction escaping oxidation is emitted to the atmosphere. The relative importance of the CH4 sources (groundwater inputs vs. sediment production) and the fraction oxidized is typically unknown, yet key for the regulation and magnitude of stream emissions. In this study, we followed the transport of CH4 from below‐stream soils to the stream water surface and to the atmosphere using a combination of CH4 concentration and stable carbon isotope gradient measurements, high resolution stream flux and discharge assessments, and inverse mass‐balance modeling. Sampling was done in multiple locations in the stream network of two independent catchments in Sweden to consider spatial variability. We show that the surface water, sub‐surface, and groundwater CH4 concentration, CH4 oxidation, and emission were highly variable in space. Our results indicate that the variability could be related to stream morphology and soil characteristics. Of the total CH4 input into the streams, roughly half of it was estimated to come from groundwater CH4 in both catchments (39% and 57%; the rest from sediment production), and most of the CH4 was oxidized (97%–99%) before emission to the atmosphere. Our results indicate that CH4 oxidation is a major sink for CH4 in the studied streams. Plain Language Summary: Streams emit a large amount of the greenhouse gas methane to the atmosphere. Sources of this methane can be groundwater and/or production in stream sediments. A part of the methane can be oxidized by microbes into carbon dioxide and the rest can evade to the atmosphere as methane. The relative magnitudes of the sources, oxidation, and emission are usually unknown but important for understanding the regulation of stream methane emissions. In this study in two stream networks of Sweden, inverse mass‐balance modeling was done using multiple measurements and we show that the sources of methane, its oxidation and emission were highly variable in space. About half of the methane in the streams was contributed by groundwater and the rest was estimated to be produced in the sediments. Most of the methane was oxidized in the streams and only a small fraction escaped to the atmosphere. Key Points: Large spatial variability in CH4 concentration, net inputs, oxidation and emission was observedRoughly half of the CH4 inputs in the streams were contributed by groundwater and the rest by sediment productionMost of the total potential stream CH4 input was oxidized before reaching the atmosphere [ABSTRACT FROM AUTHOR]

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Stream dewatering is expected to become more prevalent due to climate change, and we explored the potential consequences for brook trout (Salvelinus fontinalis) within a temperate forest ecosystem in eastern North America.We estimated fish density within stream pools (n = 386) from electrofishing surveys over 10 years (2012–2021) to compare a stream that exhibits episodic dewatering (Paine Run) against a stream of similar size that remains flow‐connected (Staunton River) within Shenandoah National Park, Virginia (U.S.A.). Annual surveys encompassed fluvial distances ranging from 2.6 to 4.4 km in each stream.Mean annual fish density (fish/pool m2) was not different between streams for juvenile or adult age classes, but spatial variation in density was greater in Paine Run for both age classes of fish. Paine Run also included a greater proportion of unoccupied pools than Staunton River and exhibited stronger spatial autocorrelation in fish density among nearby pools, suggesting dispersal limitation due to surface flow fragmentation.Fish density in pools increased during years with low summer precipitation, and this effect was observed in both streams but was stronger in Paine Run than Staunton River, further indicating the importance of fish movement into pools in response to low‐flow thresholds.Our results indicate the importance of pools as ecological refuges during low‐flow conditions and that episodic dewatering may affect extirpation risks for brook trout by sequestering more fish into fewer areas. Our findings also highlight the importance of hydrological variation within stream networks because downstream river gages could not predict the observed spatial heterogeneity in fish density or pool occupancy. [ABSTRACT FROM AUTHOR]

Motivation: The metaweb is a dictionary of nodes and their potential interactions developed for a particular region, focusing on a particular type of ecosystem. Based on the local biodiversity information at different spatial and temporal scales, the regional metaweb can be easily decomposed into local webs. The generated local webs are useful for understanding spatiotemporal variations in ecological interactions in a particular region. In this study, an attempt was made to develop a trophic metaweb for freshwater ecosystems in South Korea, called the KF‐metaweb. The metaweb contains 23,074 interactions between 446 taxa collected from 730 studies. This metaweb can be used to understand the spatiotemporal variability of different local food webs and the effects of the environment on food web properties. Furthermore, this is the first metaweb developed for any Asian ecosystem that contains information about many interactions that are unavailable in any other existing database. In addition, this metaweb study enriches our global understanding of ecological interactions. Main Types of Variables Contained: The data contained trophic interactions between resources (prey) and consumers (predators). Spatial Location and Grain: The mainland of South Korea and Jeju Island. Time Period and Grain: 2008–2021. Major Taxa: Microalgae (belonging to the phyla Cyanobacteria, Bygra, Cryophyta, Myozoa, Ochrophyta, Charophyta, Chlorophyta, Euglenozoa and Mycetozoa), zooplankton (belonging to the phyla Arthropoda and Rotifera), benthic macroinvertebrates (Platyhelmenthes, Annelida, Arthropoda and Mollusca) and fish. Level of Measurement: Minimum taxonomic resolution was at the genus level for fish and benthic macroinvertebrates and order level for zooplankton and microalgae. Software Format: Excel (*.xlsx). [ABSTRACT FROM AUTHOR]

We quantified temporal dynamics of wood storage, input, and transport over a 24‐year period in adjacent old‐growth and second‐growth forested reaches in Mack Creek, a third‐order stream in the Cascade Range of Oregon. The standing stocks of large wood in the old‐growth reach exceeded those at the second‐growth reach by more than double the number of wood pieces and triple the wood volume. Annual inputs of large wood were highly variable. Wood numbers delivered into the old‐growth reach were 3× higher and wood volume 10× greater than in the second‐growth reach. The movement of number and volume of logs did not differ significantly between the two reaches over time. Less than 2% of the logs moved in most years, and the highest proportion moved in the year of the 1996 flood (9% in old growth and 22% in second growth). Most of the large wood aggregated as jams in both reaches. The second‐growth reach lacked major jams, but 29% of the logs in the old growth were in full‐channel spanning jams. Long‐term observations of annual storage, input, and movement reveal the temporal dynamics of wood rather than static representations of the characteristics of wood. Input events and transport of wood in Mack Creek were episodic and varied greatly over the 24‐year study, which illustrates one of the major challenges and opportunities for understanding the cumulative dynamics of wood in streams. [ABSTRACT FROM AUTHOR]

Tributary valleys along the Pigeon River in southwestern Michigan USA possess many previously defined criteria for sapping valleys. Direct observations of seasonal variations in groundwater levels, hydraulic gradients and water temperatures confirm that perennial springs and their streams are present in these small valleys. Estimated spring‐fed stream discharges are low and variable, but continuous. Direct observations, grain‐size distributions and bedload transport estimates indicate that significant transport of fine to medium sand occurs in all seasons. We present a process‐form model for small‐scale sapping processes. Stream terraces and paleo‐meander scarps are being modified by sapping, and elongated valleys are likely being lengthened headward by groundwater sapping. Sapping processes have been occurring for at least the past ~4,500 years after Pigeon River adjusted to a fall in base level from the Nipissing high stand to the modern level of Lake Michigan. Sapping processes are currently producing a variety of small‐scale landforms dependent on four main factors: 1) hydraulic gradients and spring discharges, 2) available grain size of material being eroded, 3) transport rate of sand bedload by spring‐fed streams and finally 4) time available for groundwater sapping process to occur. [ABSTRACT FROM AUTHOR]

Emotions can be perceived from a person's gait, i.e., their walking style. Existing methods on gait emotion recognition mainly leverage the posture information as input, but ignore the body movement, which contains complementary information for recognizing emotions evoked in the gait. In this paper, we propose a Bilateral Posture and Movement Graph Convolutional Network (BPM-GCN) that consists of two parallel streams, namely posture stream and movement stream, to recognize emotions from two views. The posture stream aims to explicitly analyse the emotional state of the person. Specifically, we design a novel regression constraint based on the hand-engineered features to distill the prior affective knowledge into the network and boost the representation learning. The movement stream is designed to describe the intensity of the emotion, which is an implicitly cue for recognizing emotions. To achieve this goal, we employ a higher-order velocity-acceleration pair to construct graphs, in which the informative movement features are utilized. Besides, we design a PM-Interacted feature fusion mechanism to adaptively integrate the features from the two streams. Therefore, the two streams collaboratively contribute to the performance from two complementary views. Extensive experiments on the largest benchmark dataset Emotion-Gait show that BPM-GCN performs favorably against the state-of-the-art approaches (with at least 4.59% performance improvement). [ABSTRACT FROM AUTHOR]

Wildfire substantially alters aquatic ecosystems by inducing moderate to catastrophic physical and chemical changes. However, the relations of environmental and watershed variables that drive those effects are complex. We present a Driver‐Factor‐Stressor‐Effect (DFSE) conceptual framework to assess the current state of the science related to post‐wildfire water‐quality. We reviewed 64 peer‐reviewed papers using the DFSE framework to identify drivers, factors, stressors, and effects associated with each study. A total of five drivers were identified and ranked according to their frequency of occurrence in the literature: atmospheric processes > fire characteristics > ecologic processes and characteristics > land surface characteristics > soil characteristics. Commonly reported stressors include increased nutrients, runoff, and sediment transport. Furthermore, although several different factors have been used at least once to explain water‐quality effects, relatively few factors outside of precipitation and fire characteristics are frequently studied. We identified several gaps indicating the need for long‐term monitoring, multi‐factor studies, consideration of organic contaminants, consideration of groundwater, and inclusion of soil characteristics. This assessment expands on other reviews and meta‐analyses by exploring causal linkages between influential variables and overall effects in post‐wildfire watersheds. Information gathered from our assessment and the framework itself can be used to inform future monitoring plans and as a guide for modeling efforts focused on better understanding specific processes or to mitigate potential risks of post‐wildfire water quality. Plain Language Summary: Wildfires impact the hydrology and water quality of surface waters that drain burned areas. However, the environmental and watershed factors that drive post‐wildfire water quality are not well understood. We conducted a scoping review of peer‐reviewed publications to assess the current state of the science and identify knowledge gaps. Using the data gathered from the review, we developed a conceptual framework to identify factors that most frequently explain post‐wildfire impacts, the resulting stressors (i.e., changes in the system), and the effects associated with the observed stressors. Precipitation and burn severity are most frequently related to post‐wildfire impacts. Factors such as soil characteristics are studied relatively infrequently. Effects include impaired water quality, increased drinking water treatment, and increased streamflow. Our analysis identified several gaps that can be filled by long‐term monitoring, conducting studies in geographic regions affected by wildfire but where little data exists, expanding current observations to better understand shifts in baseflow contributions, and expanding chemical analyses to include organic contaminants. Key Points: Precipitation and burn severity are studied more often than soil and land characteristics to explain post‐wildfire water qualityIncreased streamflow and impaired water quality are the most documented effects of wildfire, though other effects can be importantKnowledge gaps include long‐term monitoring, multi‐factor studies, and consideration of groundwater and organic contaminants [ABSTRACT FROM AUTHOR]

Abstract Water security involves ensuring that water is available in sufficient quality and quantity to meet the needs of human health, livelihoods, ecosystems, and productive activities. This opinion paper highlights the crucial role of Long-Term Ecological Research (LTER) in shaping strategies to achieve water security. We begin by defining both water security and LTER, and by illustrating how LTER contributes to securing water resources. We then briefly discuss the significance of early long-term studies that have laid the foundation for water security efforts. Following this, we examine LTER programs focused on freshwater ecosystems in Brazil, with particular emphasis on two case studies in the Upper Paraná River: the LTER program in the Upper Paraná River floodplain and the monitoring of macrophytes in the Itaipu Reservoir. We show that long-term studies in Brazil have supported the implementation of strategies that benefit various dimensions of water security, positively impacting supporting, provisioning, regulating, and cultural ecosystem services. Finally, we discuss the incorporation of water security into Brazilian legislation. While Brazilian scientists and managers possess experience in both LTER and water security issues, ensuring the implementation and enhancement of the benefits through legislative measures and other instruments that prioritize most of the society, rather than catering solely to the most influential economic sectors is challenging.

The article presents the results of the Tutleim formation complex studies of core from 16 wells drilled on an area of 900 km2 near the Kamennaya crest of the Krasnoleninsky arch. The area is characterized by the variability of the structural plan, preserved from the time of deposits sedimentation, that might affect the structure of formation. Regionally traceable lithological units were used to describe different types of sections, which were firmly recorded on the core and on the logs. The article presents the results of the sections correlation, that shows the variability of the Tutleim formation through the area, identifies typical sections for the submerged, slope and crestal parts of the investigated field. The section may contain two reservoir intervals of different types: radiolarite and siliceousphosphate layers with average porosity values of 7% and 15%, respectively. The radiolarite layers form the main potential-productive intervals, that are found in all types of sections on one or two stratigraphic levels: in the crestal sections only in the third unit, in the slope and submerged sections – in the first, second and third units. The phosphorite layer in the fifth unit is a characteristic singularity only of the crestal sections. The obtained results allow predicting the distribution of the potential-productive intervals of the Tutleim formation and its stratigraphic analogues in different areas with higher accuracy.

Jones JR, Graham JL, Obrecht DV, Harlan JD, Knowlton MF, Pollard C, Parris J, Thorpe AP. 2024. Role of edaphic, hydrologic, and land cover variables in determining dissolved organic carbon in Missouri (USA) reservoirs and streams. Lake Reserv Manage. 40:177–195. In Missouri, distinct geophysical gradients influence statewide patterns in water quality. Here, we quantify the spatiotemporal variability of dissolved organic carbon (DOC) in reservoirs and streams and the edaphic, hydrologic, and land cover variables that account for cross-system variation. Datasets included statewide inventories collected over decades and studies with greater temporal resolution (n = >6350 DOC measurements). Among reservoirs, the smallest DOC concentration was measured in a spring-fed system within a forested watershed, and the largest was where agricultural biosolids were applied to the land (range 1.0–15.9 mg/L, overall mean 5.8 mg/L). Reservoir values increased from the southern forested Highlands (mean 4.7 mg/L) to the northern agricultural Plains (mean 7.0 mg/L). Stream DOC was similar to reservoir values (overall mean in streams 6.3 mg/L; Highlands mean 4.0 mg/L; Plains mean 6.6 mg/L), despite differences in study design and collection period. Reservoir DOC increased in spring, indicative of allochthonous loading, with small autochthonous additions during a broad summer peak. Temporal variability in DOC was low relative to macronutrients and chlorophyll in both reservoirs and streams, indicating DOC may be a sensitive and readily detected indicator of temporal change in these systems. In regression analyses, watershed features accounted for more than 60% of overall cross-system variability in DOC in both reservoirs and streams. Driver-response relations, however, differed between regions. This analysis extends our understanding of environmental influences on surface water chemistry in Missouri and indicates DOC is nearly as predictable as macronutrients using landscape-level features. [ABSTRACT FROM AUTHOR]

Stream water can serve as sources of drinking water and other domestic use. Hence, this study focused on the occurrence and antibiotic resistance of Escherichia coli (E. coli) found in streams located in Akoko Metropolis, Ondo State, Nigeria. Multiple water samples were taken from different streams in Iwaro-Oka, Akungba, Etioro, and Ayegunle. These were cultured on EMB for the presence of E. coli strains. The identity of the E. coli isolates were confirmed by microscopy and biochemical test. Antibiotic susceptibility testing (AST) was performed on the isolates by disc diffusion method using commonly used antibiotics. E. coli was isolated from all the water samples with coliform count ranging from 3.0x102 to 9.5x103 CFU/mL AST showed that 47% of the E. coli isolates were resistant to cefixime and 40% resistant to ceftriaxone. However, 80% of the isolates were susceptible to imipenem and 60% susceptible to Augmentin and nalidixic acid. The findings of this study revealed that streams can serve as potential reservoir for antibiotic-resistant E. coli which is of public health concern. In addition, it highlights the importance of monitoring and managing water quality in these areas to mitigate potential public health risks associated with antibiotic-resistant bacteria. [ABSTRACT FROM AUTHOR]

We present a checklist of Odonata (Insecta) species occurring in streams in the municipality of Araquari, northeastern state of Santa Catarina (SC), southern Brazil. Five stream reaches were surveyed bi-annually from March 2016 to March 2018. Overall, we recorded 18 taxa (16 species) from 12 genera and four families. Coenagrionidae and Libellulidae were the most species-rich families (seven species each; 43% of the total number of species recorded each). Idioneura ancilla Selys, 1860, Telagrion longum Selys, 1876 (Coenagrionidae) and Erythrodiplax umbrata (Linnaeus, 1758) (Libellulidae) are recorded for the first time in the state of Santa Catarina. Species occurrence patterns were remarkably seasonal in the studied streams, with 70% of the species recorded in the summer only, and only 25% of the species occurring in both seasons at the same stream. Our findings revealed odonate communities with marked space-time interactions in species occurrence and contribute to understand odonate biology in subtropical streams in a human-dominated landscape, and also contribute to improve the knowledge on odonate distribution in South America. Keywords: Anisoptera; aquatic insects; Atlantic Forest; streams; Zygoptera. [ABSTRACT FROM AUTHOR]

The aquatic insects of the genus Phylloicus play a crucial role in aquatic ecosystems, shredding leaves and contributing to nutrient cycling in streams. Therefore, this genus is often used in laboratory experiments. However, in Cerrado regions such as Araguaia, these studies are impractical due to a lack of knowledge about basic aspects, such as their feeding preferences for local plants. Hence, our objective is to determine the native plant species in the Araguaia region preferred as food by Phylloicus. We conducted an experimental study comparing the consumption of three native Cerrado plant species: Casearia sylvestris, Astronium fraxinifolium, and Ficus guaranítica by Phylloicus. To assess differences in consumption, we performed an Analysis of Variance. The results revealed that Phylloicus larvae exhibited a feeding preference for Casearia sylvestris (F = 9.71; p = 0.004). This finding will contribute to the development of future experimental studies using Phylloicus in the Araguaia region, as understanding the feeding preferences of animals used in experiments is essential for their maintenance in the laboratory. [ABSTRACT FROM AUTHOR]

Broad‐scale mapping of stream channel and floodplain geomorphic metrics is critical to improve the understanding of geomorphic change, biogeochemical processes, riverine habitat quality, and opportunities for management intervention. The Floodplain and Channel Evaluation Tool (FACET) was developed to provide an open‐source tool for automated processing of digital elevation models (DEMs) to generate regional‐scale estimates of bank height, channel width, floodplain width, and a suite of other fluvial geomorphic dimensions that can be summarized at the stream reach‐ or catchment‐scale. FACET was tested on 3‐m DEMs covering the Delaware River watershed and 85% of the Chesapeake Bay watershed in the United States (U.S.) and on 1‐m DEMs for a subset of the study area. Accuracy was assessed from data collected at 67 field sites in the study area. FACET successfully measured geomorphometry for over 270,000 stream reaches (88% of streams attempted) in the study area. Factors that reduced the ability of FACET to accurately estimate geomorphic metrics included errors in DEM hydro‐conditioning, gradually sloping banks, incised stream channels, and the use of fixed input parameters to define buffer lengths. Even with these limitations, FACET was able to map regional patterns in stream and floodplain geomorphometry providing a robust dataset that can enhance modeling and management efforts throughout the mid‐Atlantic region, U.S. [ABSTRACT FROM AUTHOR]

Objective: Altered flow regimes pose significant risks to the stability of populations of riverine Smallmouth Bass Micropterus dolomieu. Periods of poor recruitment, due to early life stage mortality resulting from high-flow events, can cause size-structure and density alterations of populations. The aim of this study was to opportunistically test for changes in dynamic rates of a riverine Smallmouth Bass population using a long-term data set that spanned a period of poor recruitment. Methods: Our study evaluated size-specific CPUE (fish/h), mortality, growth, and condition and tested for recruitment determinants of Smallmouth Bass through three consecutive years of poor age-0 recruitment in the South Branch Potomac River, West Virginia. We used fall nighttime boat electrofishing surveys during 2009-2022 to monitor this population before and after the poor-recruitment time frame (2016-2018). Result: Age-0 CPUE was greater during the time frame prior to the poor-recruitment time frame. However, there was no difference in the CPUE of quality-length Smallmouth Bass between the two time frames and CPUE of preferred-length fish was greater during the poor-recruitment time frame. Growth and relative weight increased during the poor-recruitment time frame. There was no significant difference detected in mortality between the recruitment time frames. Streamflow during the spawning period was a significant factor influencing fall recruitment of age-0 Smallmouth Bass. A Ricker density-dependent model with an added streamflow term performed as well as a basic, log-linear streamflow model and a density-independent model that also incorporated a streamflow term. Conclusion: Our results provide evidence of density-dependent structuring in this population. Decreases in population density increased population dynamic rates that maintained or improved size structure. High adult biomasses did not increase age-0 recruitment. Many riverine Smallmouth Bass populations may display favorable density-dependent responses to declines in juvenile recruitment. Thus, management agencies should better understand the resiliency of these populations prior to establishing expensive programs or regulations, which may be ineffective, to combat alterations in juvenile recruitment. [ABSTRACT FROM AUTHOR]

Context: Global change, including land-use change and habitat degradation, has led to a decline in biodiversity, more so in freshwater than in terrestrial ecosystems. However, the research on freshwaters lags behind terrestrial and marine studies, highlighting the need for innovative approaches to comprehend freshwater biodiversity. Objectives: We investigated patterns in the relationships between biotic uniqueness and abiotic environmental uniqueness in drainage basins worldwide. Methods: We compiled high-quality data on aquatic insects (mayflies, stoneflies, and caddisflies at genus-level) from 42 drainage basins spanning four continents. Within each basin we calculated biotic uniqueness (local contribution to beta diversity, LCBD) of aquatic insect assemblages, and four types of abiotic uniqueness (local contribution to environmental heterogeneity, LCEH), categorized into upstream land cover, chemical soil properties, stream site landscape position, and climate. A mixed-effects meta-regression was performed across basins to examine variations in the strength of the LCBD-LCEH relationship in terms of latitude, human footprint, and major continental regions (the Americas versus Eurasia). Results: On average, relationships between LCBD and LCEH were weak. However, the strength and direction of the relationship varied among the drainage basins. Latitude, human footprint index, or continental location did not explain significant variation in the strength of the LCBD-LCEH relationship. Conclusions: We detected strong context dependence in the LCBD-LCEH relationship across the drainage basins. Varying environmental conditions and gradient lengths across drainage basins, land-use change, historical contingencies, and stochastic factors may explain these findings. This context dependence underscores the need for basin-specific management practices to protect the biodiversity of riverine systems. [ABSTRACT FROM AUTHOR]

ABSTRACT We aimed to characterize the floristic composition, detect the life forms, and provide an identification key for the macrophyte species of the Capitão Poço river micro-basin in the State of Pará, located in the Eastern Amazon. The collected specimens were identified and deposited in the HCP herbarium. We found 23 species distributed in 19 genera and 14 families of macrophytes. The families with the highest species richness were Cyperaceae (six spp.), Poaceae (three spp.), Onagraceae and Plantaginaceae (two spp. each). We present here the first record of Dichanthelium aequivaginatum from the Brazilian Amazon and the Northern region of Brazil. We suggest that floristic-taxonomic studies of macrophytes in the hydrographic basins of the northeastern region of Pará should be intensified in order to better understand the regional flora of this group.

The Nooksack Dace (Rhinichthys cataractae sp. cataractae) is a federally endangered riffle specialist endemic to the lower Fraser Valley of British Columbia, Canada, with historic population declines associated with riffle loss from stream dredging, channelization, and excessive sediment inputs. To assess the effectiveness of riffle restoration as a recovery strategy, gravel and cobble riffles were constructed in two replicate tributaries of the Nooksack River as a before-after-control-impact experiment, measuring dace abundance, substrate composition, and invertebrate biomass before and one year after restoration. Nooksack Dace density increased significantly in cobble (but not gravel) treatments relative to control riffles. Dace abundance was strongly associated with increased availability of interstitial refuges rather than substrate effects on invertebrate prey abundance, suggesting that interstitial space limits adult dace abundance. Young-of-the-year dace were not observed in one of the two restored streams despite riffle restoration, indicating increased dace density due to aggregation in higher-quality restored riffles. This recruitment limitation indicates persistence of a population bottleneck at an early life history stage that is not addressed by successful restoration of adult riffle habitat.

Aim: Understanding the roles of deterministic and stochastic processes in community assembly is essential for gaining insights into the biogeographical patterns of biodiversity. However, the way community assembly processes operate is still not fully understood, especially in oceanic islands. In this study, we examine the importance of assembly processes in shaping diatom communities in islands and continents, while also investigating the influence of climate and local water chemistry variables on species distributions. Location: Global. Taxon: Stream benthic diatoms. Methods: We used diatom datasets from five continents and 19 islands and applied beta diversity analyses with a null model approach and hierarchical joint species distribution modelling. To facilitate comparisons with continents, we used continental area equivalents (CAEs), which represent continental subsets with comparable areas and the same number of study sites as their corresponding islands counterparts. Results: We found that homogeneous selection (i.e., communities being more similar than the random expectation) was the dominant assembly process within islands whereas stochastic processes tended to be more important within continents. In addition, assembly processes were influenced by study scale and island isolation. Climatic variables showed a greater influence on species distribution than local factors. However, in islands, local environmental variables had a greater impact on the distributions of unique taxa as opposed to non‐unique taxa. Main Conclusions: We observed that the assembly processes of diatom communities were complex and influenced by a combination of deterministic and stochastic forces, which varied across spatial scales. In islands, there was no universal pattern of assembly processes, given that their influence depends on abiotic conditions such as area, isolation, and environmental heterogeneity. In addition, the sensitivity of species occurring uniquely in islands to local environmental variables suggests that they are perhaps less vulnerable to climatic changes but may be more influenced by changes in local physicochemistry. [ABSTRACT FROM AUTHOR]

As climate change accelerates, low summer stream flows are becoming increasingly common in the Colorado Rocky Mountains, USA. The diatom Didymosphenia geminata (Lyngb.) M. Schmidt, typically observed under low-flow and low-P conditions, produces nuisance growth—persistent and extensive proliferation, covering the bottoms of streams in thick algal mats. Nuisance blooms of this diatom physically alter the benthic environment and thereby affect freshwater invertebrates directly and indirectly by altering stream food webs. We compared 9 y of survey data (2013–2021) of D. geminata proliferation with the composition of the macroinvertebrate communities at 8 stream sites near the Rocky Mountain Biological Laboratory in western Colorado. We counted and identified samples of benthic macroinvertebrates and used a glass-bottomed viewing box to estimate D. geminata biovolume at 2 scales: macrohabitat conditions (site level: 2013–2021) and microhabitat conditions (sample level: 2020–2021). At both scales, increases in D. geminata proliferation were associated with shifts in macroinvertebrate community composition that could be explained by altered abundances of focal taxa, specifically declines in Heptageniidae (Ephemeroptera) and increases in Chironomidae (Diptera). Abundances of Baetidae (Ephemeroptera) were unaffected by increased D. geminata biovolume. These changes indicate degradation of stream habitat for some sensitive groups of macroinvertebrates, which may affect higher trophic levels, such as trout, in these mountain stream ecosystems. As climate change trends toward lower summer streamflow, understanding the effects of proliferation of this ecosystem engineer is key to predicting the impact of climate change on stream food webs. [ABSTRACT FROM AUTHOR]

Simple Summary: Endemism is a hallmark of unique environments. Recognizing endemism, however, often depends on the ability to discriminate among structurally similar (cryptic) species. We used the giant polytene chromosomes of larvae to reveal a new species of black fly in the Djurdjura Mountains of northern Algeria. The female, male, pupa, and larva, in addition to the giant chromosomes, are described and compared with those of similar species. This new species is probably restricted to the mountains of the Mediterranean coast and perhaps exclusively to Algeria, making it the first endemic species of black fly recorded from the country. Recognition of this new species as endemic highlights the unique nature of the environment and provides additional rationale for conservation of aquatic habitats in the area. 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. [ABSTRACT FROM AUTHOR]

Increases in the intensity and frequency of wildfres highlight the need to understand how fre disturbance afects ecological interactions. Though the efects of wildfre on free-living aquatic communities are relatively well-studied, how host–parasite interactions respond to fre disturbance is largely unexplored. Using a Before-After-Control-Impact design, we surveyed 10 stream sites (5 burned and 5 unburned) in the Willamette River Basin, Oregon and quantifed snail host infection status and trematode parasite community structure 1 year before and two years after historic wildfres. Despite the severity of the wildfres, snail host populations did not show signifcant shifts in density or size distributions. We detected nine taxa of trematode parasites and overall probability of infection remained consistent over the three-year study period. However, at the taxon-specifc level, we found evidence that infection probability by one trematode decreased and another increased after fre. In a larger dataset focusing on the frst year after fre (9 burned, 8 unburned sites), we found evidence for subtle diferences in trematode community structure, including higher Shannon diversity and evenness at the burned sites. Taken together, host–parasite interactions were remarkably stable for most taxa; for trematodes that did show responses, changes in abundance or behavior of defnitive hosts may underlie observed patterns. These results have implications for using parasites as bioindicators of environmental change and suggest that aquatic snail-trematode interactions may be relatively resistant to wildfre disturbance in some ecosystems. [ABSTRACT FROM AUTHOR]

The relative frequency of sexual versus asexual reproduction governs the distribution of genetic diversity within and among populations. Most studies on the consequences of reproductive variation focus on the mating system (i.e., selfing vs. outcrossing) of diploid‐dominant taxa (e.g., angiosperms), often ignoring asexual reproduction. Although reproductive systems are hypothesized to be correlated with life‐cycle types, variation in the relative rates of sexual and asexual reproduction remains poorly characterized across eukaryotes. This is particularly true among the three major lineages of macroalgae (green, brown, and red). The Rhodophyta are particularly interesting, as many taxa have complex haploid–diploid life cycles that influence genetic structure. Though most marine reds have separate sexes, we show that freshwater red macroalgae exhibit patterns of switching between monoicy and dioicy in sister taxa that rival those recently shown in brown macroalgae and in angiosperms. We advocate for the investigation of reproductive system evolution using freshwater reds, as this will expand the life‐cycle types for which these data exist, enabling comparative analyses broadly across eukaryotes. Unlike their marine cousins, species in the Batrachospermales have macroscopic gametophytes attached to filamentous, often microscopic sporophytes. While asexual reproduction through monospores may occur in all freshwater reds, the Compsopogonales are thought to be exclusively asexual. Understanding the evolutionary consequences of selfing and asexual reproduction will aid in our understanding of the evolutionary ecology of all algae and of eukaryotic evolution generally. [ABSTRACT FROM AUTHOR]

The construction of roads can generate threats to the biodiversity of an important hydrological network made up of streams known as quebradas in the Peruvian Amazon. The objective of the study was to determine the composition, richness, abundance, diversity, dominance, and similarity of habitats of benthic macroinvertebrate communities of five streams located around the Iquitos-Nauta highway axis (Loreto, Peru). The collections were made in four periods (empty, dry, growing, and full), using a D-net type network. The benthic macroinvertebrate community was composed of 68 taxa and 4556 individuals, distributed in 4 phyla (Arthropoda, Annelida, Mollusca and Nematoda). The similarity analysis indicates that there were significant differences (p < 0.05) between the empty-dry seasons and the growing-full seasons; The dry season being the one with the greatest value of wealth, abundance, and diversity; and increasing the one with greater dominance. Chironomidae, Leptophlebiidae, Elmidae and Palaemonidae; were the most dominant taxa. The present work is a contribution to the knowledge of the macroinvertebrate communities that inhabit the small lotic ecosystems of the Peruvian lowland forest. [ABSTRACT FROM AUTHOR]

Recruitment failure is a major threat to freshwater mussel (Order Unionida) populations worldwide. Assessments of the recruitment status and determining the bottleneck factors of mussel recruitment are crucial for preventing future declines in mussel populations. In this study, we investigated the recruitment status (i.e., size structure and the proportion of juveniles within a population) of the endangered freshwater pearl mussel Margaritifera laevis in 22 rivers, represented by two reaches at one study site, in eastern Hokkaido, northern Japan. We also quantified the density of the host fish Oncorhynchus masou masou and examined the relationship between the proportion of juveniles and host-fish density to assess host-limitation threats to M. laevis recruitment. Our assessments showed that 13 (59.1%) sites had no signs of recent recruitment within 10 years, with a low mean proportion of juveniles [mean: 0.02 (range 0.00–0.09) fraction], indicating that these populations are threatened by sustained recruitment failure. The proportion of juveniles was positively associated with host-fish density, suggesting that host-fish limitation could be a bottleneck factor for M. laevis recruitment. These results highlight the urgent need for prompt conservation measures, including the enhancement of host-fish availability, to sustain M. laevis populations in the study region. [ABSTRACT FROM AUTHOR]

We study connections among polynomials, differential equations, and streams over a field , in terms of algebra and coalgebra. We first introduce the class of (F,G)-products on streams, those where the stream derivative of a product can be expressed as a polynomial function of the streams and their derivatives. Our first result is that, for every (F,G)-product, there is a canonical way to construct a transition function on polynomials such that the resulting unique final coalgebra morphism from polynomials into streams is the (unique) commutative -algebra homomorphism—and vice versa. This implies that one can algebraically reason on streams via their polynomial representation. We apply this result to obtain an algebraic-geometric decision algorithm for polynomial stream equivalence, for an underlying generic (F,G)-product. Finally, we extend this algorithm to solve a more general problem: finding all valid polynomial equalities that fit in a user specified polynomial template. [ABSTRACT FROM AUTHOR]

Stream ecosystems are actively involved in the biogeochemical cycling of carbon (C) and nitrogen (N) from terrestrial and aquatic sources. Streams hydrologically connected to peatland soils are suggested to receive significant quantities of particulate, dissolved, and gaseous C and N species, which directly enhance losses of greenhouse gases (GHGs), i.e., carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O), and fuel in-stream GHG production. However, riverine GHG concentrations and emissions are highly dynamic due to temporally and spatially variable hydrological, meteorological, and biogeochemical conditions. In this study, we present a complete GHG monitoring system in a peatland stream, which can continuously measure dissolved GHG concentrations and allows to infer gaseous fluxes between the stream and the atmosphere and discuss the results from March 31 to August 25 at variable hydrological conditions during a cool spring and warm summer period. Stream water was continuously pumped into a water-air equilibration chamber, with the equilibrated and actively dried gas phase being measured with two GHG analyzers for CO2 and N2O and CH4 based on Off-Axis Integrated Cavity Output Spectroscopy (OA-ICOS) and Non-Dispersive Infra-Red (NDIR) spectroscopy, respectively. GHG measurements were performed continuously with only shorter measurement interruptions, mostly following a regular maintenance program. The results showed strong dynamics of GHGs with hourly mean concentrations up to 9959.1, 1478.6, and 9.9 parts per million (ppm) and emissions up to 313.89, 1.17, and 0.40 mg C or N m−2h−1 for CO2, CH4, and N2O, respectively. Significantly higher GHG concentrations and emissions were observed shortly after intense precipitation events at increasing stream water levels, contributing 59% to the total GHG budget of 762.2 g m−2 CO2-equivalents (CO2-eq). The GHG data indicated a constantly strong terrestrial signal from peatland pore waters, with high concentrations of dissolved GHGs being flushed into the stream water after precipitation. During drier periods, CO2 and CH4 dynamics were strongly influenced by in-stream metabolism. Continuous and high-frequency GHG data are needed to assess short- and long-term dynamics in stream ecosystems and for improved source partitioning between in-situ and ex-situ production.