Search

Headwater streams are critical, fragile ecosystems that supply food and nutrients for an array of organisms that are vital to the overall health of a stream. As the dominant vertebrates in headwater streams of the southern Appalachian Mountains, plethodontid salamanders are critical to healthy headwater communities. However, a neglected feature of these ecosystems is the community of parasites that infect salamanders. The digenetic trematode Metagonimoides oregonensis uses the aquatic snail Elimia proxima as its first intermediate host and the plethodontid salamander Desmognathus amphileucus as its second intermediate host. In a series of southern Appalachian streams, we tested the hypothesis that variance in the prevalence and intensity of infection in salamander hosts is related to respective densities of the snail and salamander species. Infection prevalence was 100% across all streams. There was a strong relationship between the density of the snail host and infection-intensity level in the salamander host. However, the relationship with salamander density was not important, a finding that conflicts with the results of parasitological studies involving lentic and marine systems. The influence of this trematode on the ecology of headwater streams and the resident salamanders has been underappreciated, and a number of aspects of this relationship remain unknown. [ABSTRACT FROM AUTHOR]

This paper moves across the ecological assemblages of the Periyar basin in Kerala. It argues that the connectivities and unintentional designs that emerge bespeak the Anthropocene in its regional and political peculiarities. The river has never been a conduit of water alone. The narrative builds broadly on ecological relations entrenched in history, most visibly as hydrological regimes. Such regimes are significant because of the riparian densities that articulate the geo‐morphology. The different entanglements in ecology, as well as the successive productions of natures, gain significance as 'recognitions' during rupture events like the large floods. In contemporary contexts, the versatile flows of capital dissolve markers and boundaries and reconfigure regions in terms of capital. Vikasanam or new urban reforms, apart from political policies, are also ecological designs that normalise exceptions, otherwise reserved for special economic zones. The frictions with new materiality, post dam floods and hydrological controls, during developmental and neoliberal post developmental phases, become moments of recognition, making and unmaking sense of place. [ABSTRACT FROM AUTHOR]

Freshwater salinization increasingly threatens river ecosystems in arid regions. In situ studies on effects of salinity on freshwater communities are still scarce, especially in largely understudied areas of Africa. To compare macroinvertebrate communities in differing salinity levels, we conducted a confluence-based study in the Draa River basin in Morocco by focusing on two tributaries and their joint downstream sections, in the immediate vicinity of three confluences. Our study revealed that α-diversity differed only minimal. Although only around five taxa comprised over 90% of specimens per section, the more saline sections exhibited proportionally more salt-tolerant generalist species. There was lower β-diversity between the downstream section and each tributary compared to between tributaries, indicating a mixed community after the confluence. The trait profile of the saline El Mellah displayed more resistance and resilience traits to disturbances than the less saline Iriri. Furthermore, low water flow reduced the abundance of sensitive taxa. Overall, we observed minimal differences in macroinvertebrate community composition, due to low γ-diversity in the basin. However, the confluence-based study design remains valuable for investigating effects of specific stressors on ecosystems by excluding large-scale geographic patterns, as compared sites are close and therefore share the same climate, geology, and altitude. [ABSTRACT FROM AUTHOR]

The article announces the 2023 class of Fellows for the American Association for the Advancement of Science (AAAS), recognizing 502 members for their contributions to science and society.

Understanding the impacts of habitat modification on primate feeding ecology is essential to design effective conservation management strategies. The dietary guild (e.g., frugivore, folivore, insectivore, and omnivore) of primates and their degree of ecological flexibility impacts their ability to cope with human-modified habitats. The Omo River guereza (Colobus guereza guereza) is a subspecies of eastern black-and-white colobus monkey endemic to the western Rift Valley forests of Ethiopia, where it faces increasing anthropogenic change. While there is some understanding of how this subspecies copes with anthropogenic pressures, we compared the feeding ecology of Omo River guerezas in natural and human-modified habitats. Specifically, we collected data on two neighbouring guereza groups that inhabit adjacent plantation and natural forest habitats over 12 months in Wof-Washa Natural State Forest in the central highlands of Ethiopia. Furthermore, we conducted vegetation surveys on the botanical composition and vertical structure of both habitat types. The monthly food availability index of young leaves was higher in the natural forest than in plantation forest habitat. We observed guerezas feeding on 30 plant species in the natural forest but only 18 species in the plantation forest. Guerezas in both forest types consumed mostly young leaves, but the natural forest group relied more on mature leaves and shoots, and less on fruits and stems, than the plantation forest group. Maesa lanceolata leaves contributed a greater proportion of the overall diet for the plantation forest group, whereas Vernonia leopoldi accounted for the largest proportion of the guereza diet for the natural forest group. The top five species consumed comprised 83% of the diet in the plantation forest group and 70% in the natural forest group, indicating that relatively few plant species dominate guereza diets in these habitats. Conservation of both natural and plantation forests, especially the plant species most intensively exploited by guerezas, should be prioritized to assist in Omo River guereza conservation efforts. [ABSTRACT FROM AUTHOR]

River typology is determined by a set of hydrological and geomorphological characteristics, which can determine the structure of aquatic macroinvertebrate communities throughout a watershed. In this study we aim to address the gap of knowledge in the classification of the typology of Neotropical rivers and determine their association with macroinvertebrate assemblages. In total, 138 sites from 107 rivers were sampled in Costa Rica, between years 2015 and 2020. Rivers were classified into V, Tr and U typologies based on the shape of the riverbed, substrates, current velocity and contact with riparian forest. The affinity of aquatic macroinvertebrate taxa to each typology was determined. The results confirmed a clear separation of the aquatic macroinvertebrate assemblages between the typologies, and we observed that some genera showed affinity to a specific typology: Macrobrachium and Caenis are related to U-type; Simulium and Anacroneuria to V-type, while Americabaetis and Thraulodes to Tr-type. This separation was related to in-stream habitat supply and substrate characteristics, yet there was an overlap of shared taxa between the V and Tr-type, and between the Tr and U-type. Our study linked 238 taxa to three river typologies, highlighting the importance of river hydrogeomorphology as a robust factor structuring the macroinvertebrate assemblages in tropical streams. River channel typology should be considered a relevant explanatory variable when studying macroinvertebrate responses, not only within ecological studies, but also for biomonitoring and risk assessment related to land use changes, pollution, or watershed management. [ABSTRACT FROM AUTHOR]

Traditional river health assessment relies on limited water quality indices and representative organism activity, but does not comprehensively obtain biotic and abiotic information of the ecosystem. Here, we propose a new approach to evaluate the ecological and health risks of river aquatic ecosystems. First, detailed physicochemical and biological characterization of a river ecosystem can be obtained through pollutant determination (especially emerging pollutants) and DNA/RNA sequencing. Second, supervised machine learning can be applied to perform classification analysis of characterization data and ascertain river ecosystem ecology and health. Our proposed methodology transforms river ecosystem health assessment and can be applied in river management. [Display omitted] [ABSTRACT FROM AUTHOR]

This document is a preface to a special issue of the journal Hydrobiologia on the topic of stream ecology and environmental gradients. The preface explains that human activities have fragmented natural landscapes, leading to changes in environmental gradients and a decline in biodiversity. The document highlights the importance of understanding the effects of environmental gradients on aquatic communities and ecosystem services. The special issue includes 10 papers from authors of various nationalities, focusing on the effects of land use, vegetation cover, water pollution, and other disturbances on diatoms, macroinvertebrates, and fish communities. The studies demonstrate that environmental gradients can alter water quality, habitat availability, and the structure and composition of aquatic communities. The document concludes by expressing gratitude to the reviewers and authors who contributed to the special issue. [Extracted from the article]

In urban and agricultural streams, assessing aquatic ecosystem health is critical due to widespread pollution. Traditional methods for evaluating attached diatoms crucial for ecosystem monitoring face limitations such as species misidentification and sample damage. This study was conducted in the Miho River within the Geum River system and highlights the effectiveness of environmental DNA (eDNA) techniques for more accurate and efficient genetic-based analysis than conventional microscopic analysis methods. When eDNA-based assessments were compared with traditional microscopic methods, this study found that eDNA analysis often revealed poorer ecosystem health. Notably, eDNA assessments showed a stronger correlation with phosphorus concentrations, underlining their precision and importance in ecological studies. These findings suggest that eDNA has potential as a valuable tool for comprehensive biomonitoring. However, the use of international genetic barcode databases in eDNA analysis could lead to the identification of unrecorded species in Korea. Therefore, this study recommends developing a localized genetic barcode database and constructing eDNA information through meta-barcoding, focusing on native species. This approach is crucial for enhancing the accuracy and applicability of eDNA-based health assessments in national biomonitoring efforts. [ABSTRACT FROM AUTHOR]

Water conservation initiatives satisfy the demand for water supply, electricity generation, irrigation, and flood control. While helping humanity, they have also altered the ecosystem of natural rivers, impacted river ecology, disrupted river continuity, and jeopardized the existence of aquatic creatures in rivers. Studying the impacts of dam construction on rivers can enhance our knowledge of river ecological and environmental concerns and help sustain the health of river ecosystems, thereby realizing the harmony between humans and water in both theoretical and practical aspects. This study used bibliometrics and constructed an author-keyword 2-mode matrix network using Co-Occurrence software to identify the hotspots and research trend in eco-hydrology of dammed rivers. We identified 'FLOW' 'SEDIMENT' 'QUALITY' and 'MODEL' as the research hotspots in the ecological impact of dammed rivers, and combined the related literatures, we highlight the research progress in the four directions. Then the research shortcomings and prospect were discussed, including strengthening the monitoring and analysis of critical ecological variables, enhancing the hydrological monitoring density for small rivers, strengthening the research of relationship between eutrophication and zooplankton, establishing multiscale approaches, and combining multi-sources information technologies to improve parameter accuracy in the model research. [ABSTRACT FROM AUTHOR]

The fragile ecology of the Yellow River basin (YRB) is vulnerable to global warming and human activities. As the second largest river in China, the YRB covers the subhumid, semi‐arid, arid and alpine climate zones, with considerably spatial differences in vegetation cover (VC), thus demonstrating substantial variations in response to climate change. In this study, characteristics of VC variations in different climate zones of the YRB during 1982–2019 were analysed, impacts of climate change and human activities on VC variations were identified, and possible VC variations in the future were projected under different climate scenarios. Results show that NDVI in the YRB significantly increased at a rate of 2.3 × 10−3 year−1 from 1982 to 2019, especially in the middle reaches of the YRB. Temperature is the main driver of VC variations in the source region of the YRB (alpine zone), wherein the warming trend contributes to the greening. The internal variability of VC is also influenced by temperature, with a marginal effect of precipitation minus evaporation (P − E). In the middle and lower reaches of the YRB consisting of arid, semi‐arid, and subhumid zones, VC benefited only from the warming trend and had a less relationship with the internal variability of temperature, whereas the internal variability of VC was influenced by P − E and had a weaker relationship with the P − E trend. Contributions of climate change to VC variations in the source region and middle and lower reaches of the YRB are approximately 62%, 42%, and 27%, respectively. Human activities considerably impact the ecological environment but mostly play a positive role. In the future, VC will increase in the YRB, especially under the SSP5‐8.5 scenario, and VC reveals the most prominent changes in the lower reaches. This study suggests that climate change might be favourable to VC in YRB, and emphasizes that human activities should adapt to climate change in an orderly manner. [ABSTRACT FROM AUTHOR]

The current study investigated the relationship between sediment grain sizes and macroinvertebrate distribution along the Isiukhu River, a tropical stream in western Kenya. Ten sites in total were selected from the upstream, midstream and downstream areas. Sampling of sediments and macroinvertebrates was carried out twice a month from March 2018 to March 2019. Sediment was characterised as polymodal and extremely poorly sorted at the upstream; trimodal and extremely poorly sorted in the midstream; and polymodal and extremely poorly sorted towards the downstream of the river. Upstream sediments were fine gravelly mud and very coarse gravelly mud, while downstream sediments were very coarse gravelly muddy very fine sand and very fine gravelly, clayey very fine sand, indicating sediments became finer downstream. The study identified 993 individual macroinvertebrates from 21 families. Highest mean abundance (100 ± 9.2) was recorded at Kimangeti (upstream) while least was at Mutono (11 ± 0.7) (downstream). A regression model of the relationship between mean sediment grain size and mean macroinvertebrate abundance indicated that sediment grain size accounted for 28.7% of the spatial variability of macroinvertebrate abundance. The connection between sediment size and macroinvertebrate abundance and diversity in the Isiukhu River highlights that control of soil erosion in this catchment is important for the ecology of this river. [ABSTRACT FROM AUTHOR]

1.Dams on large rivers alter hydrodynamics, reduce seasonal variability and environmental heterogeneity, and have significant effects on river ecology. They produce less diverse environments and alter the community composition. Knowledge about the effects of dams on functional aspects of zooplankton communities is scarce. Thus, our main goal was to investigate how the zooplankton community of the Tocantins River in central Brazil changed after the implementation of the Estreito hydroelectric power plant dam. We explored the relationships of taxonomic and functional beta diversity in the zooplankton community, with the seasonality, flooding river phases and limnological variables.2.To answer our goals, we collected water samples 1 year before plant construction and 5 months after dam enclosure. To investigate how the environment changed after river damming, we conducted a principal component analysis. We calculated taxonomic and functional beta diversity using the Jaccard pairwise dissimilarity index for presence–absence data. To identify which functional traits were associated with each river phase and season, we firstly calculated the community weighted mean (CWM) for each trait. Secondly, we partitioned beta diversity into turnover and nestedness components. To investigate patterns of taxonomic and functional beta diversity and its turnover and nestedness components, we additionally used a series of six linear mixed models.3.Our results indicated that the limnological characteristics of the river changed after damming. Taxonomic and functional turnover was higher during the pre‐inundation phase, and this phase also showed greater limnological heterogeneity in comparison to the post‐inundation phase. We observed a strong seasonal dynamic in taxonomic turnover, with high turnover during the dry season. However, these seasonal dynamics disappeared after river damming. We demonstrated that the patterns of taxonomic and functional beta diversities were influenced by limnological variables and seasonal dynamics, which resulted in reduced variability in both species composition and functional characteristics after the implementation of the reservoir.4.This study emphasises the importance of variations in annual flow regimes in lotic ecosystems. We also showed an association between environmental heterogeneity patterns the high taxonomic and functional diversity of zooplankton communities. [ABSTRACT FROM AUTHOR]

Urban streams are impacted by multiple anthropogenic environmental stressors that exert considerable pressure on resident fish populations. Species such as brook trout (Salvelinus fontinalis) are particularly vulnerable because urban environments typically limit the cold oxygenated water required by all life stages. To understand factors associated with native brook trout movement in urban streams, we monitored 20 radio-tagged individuals from late summer through the spawning season in autumn, and modelled how movement was influenced by body size and habitat. Tracking occurred in two adjacent streams that differed in forest cover and channelization. In both streams, brook trout mainly travelled upstream, particularly at the onset of the autumn spawning season. Larger individuals exhibited greater movements, and habitat complexity imposed stronger effects in larger individuals. Greater movements were made into locations of shallower depth and lower conductivity, although these factors were conflated with movement into upstream locations. This study addresses a fundamental knowledge gap in urban stream ecology by providing detailed information on the movement of a key indicator species of aquatic ecosystem health. [ABSTRACT FROM AUTHOR]

When multiple species with similar trophic niches co-occur in an ecosystem, foraging, refuge, and breeding microhabitats are predicted to be partitioned in order to enable their coexistence. However, few studies have examined potential niche partitioning among vertebrates with a bi-phasic natural history, such as stream salamanders. In addition to microhabitat, the coexistence of multiple species and life-stages is likely facilitated by the partitioning of diet. As plethodontid stream salamanders have an aquatic larval stage and a semi-aquatic adult stage (i.e., post-metamorphic), the diets of multiple species and life-stages can elucidate patterns in their community structure. Specifically, dietary overlaps can be used to evaluate the level of niche overlap and thus, potential competition among different species and life-stages. In this study, we non-lethally examined the dietary overlap among five predacious aquatic larval and three semi-aquatic adult stream salamander species in southeastern Kentucky. Our data illustrated both inter- and intra-specific dietary overlaps among the stream salamander community. We additionally observed dietary overlaps among all adult salamanders and their larval counterparts. We found differential dietary clustering and separation among some of the species and life-stages. Though not directly tested in this study, our results are suggestive of selection/constraint to species- and life-stage-specific foraging microhabitats. [ABSTRACT FROM AUTHOR]

At present, most research on the optimal scheduling of hydropower stations in the day-ahead electricity market focuses on the optimal power generation benefit, which does not consider the ecological impact of the generated discharge flow on downstream rivers. To address this situation, the ecological impact of electricity markets on rivers downstream of annually regulated hydropower stations is studied, and adjustment methods for traditional scheduling methods are proposed to achieve better ecological benefits. To this end, a multitimescale nested forecasting scheduling model is proposed for simulating hydropower station scheduling. In addition, the ecological flow index of the distribution flow method, an easy-to-implement ecological indicator model, was used to quantify the ecological benefits of discharge flows. A hydropower station on the upper course of the Lancang River in China was used to analyze the electricity market's impact on downstream river ecology. The results show that under the optimal power generation benefit scheme, the ecological benefits are influenced not only by electricity price characteristics but also by multitimescale nested scheduling. Based on an analysis of these two factors, the general rules for the ecological benefits of rivers downstream of annually regulated hydropower stations in the day-ahead electricity market are summarized. In addition, the relationship between power generation and ecological benefits is analyzed for various schemes in a multiobjective scheduling problem framework. Finally, adjustment methods for traditional scheduling methods are proposed to achieve better ecological benefits. [ABSTRACT FROM AUTHOR]

River–floodplain ecosystems play a crucial role in connecting landscape patches through hydrological connectivity, but they are among the most threatened ecosystems. Floodplains provide important habitat for amphibians by connecting aquatic and terrestrial habitats. Modifications to floodplain hydrology can impact amphibian communities, yet few studies have examined amphibian metacommunities in floodplain wetlands.In this study, we assessed patterns in amphibian breeding abundance in one of the largest floodplains of the Danube River, Hungary, relative to hydrological connectivity and multi‐scale variables at 30 waterbody sites. Our aim was to determine whether these patterns aligned with the pond‐permanence gradient hypothesis, where breeding amphibian abundance is predicted to be highest in ephemeral ponds without large predatory fish. We used Bayesian hierarchical modelling to estimate multi‐species abundance from repeated survey (count) data collected over one breeding season.We detected the eggs and larvae of four amphibian species. The best model of abundance included covariates describing two principal component axes associated with waterbody hydrology and landscape composition within a 500‐m radius of a site. There was a positive relationship between mean community abundance at a site and hydrological disconnection from the main river channel; however, the common toad (Bufo bufo) was associated with hydrologically connected waterbodies. There was a positive relationship between mean community abundance and a high proportion of forest cover and low cover of agricultural land within a 500‐m radius around a site, although this relationship was clear for only two species. There was no support for models containing the number of large predatory fish species detected at a site.Although our results showed that amphibian abundance declined with hydrological connectivity, based on model selection we could not ascribe this relationship to an increased number of large predatory fish species detected in waterbodies close to the main river channel. Differences in life history and habitat requirements are likely to have explained interspecific responses to hydrological connectivity. Our results underscore the importance of addressing amphibian abundance at multiple spatial scales in floodplain wetlands, as landscape composition partly explained patterns in abundance.Application of multi‐species abundance modelling allowed us to investigate environmental relationships for common and infrequently detected species. Habitat restoration programmes in floodplains should provide waterbodies disconnected from main river channels as potential amphibian breeding sites and protect or restore forest as terrestrial habitat. [ABSTRACT FROM AUTHOR]

River hydrology is an important proxy for changes in river runoff and an important factor affecting the ecology of rivers. To quantitatively evaluate the hydrology of the Wuijang River basin, this paper uses various tests to analyze runoff. The IHA-RVA method combined with FDC ecohydrological indicators was used to evaluate the hydrology of the Wuijang River basin and to analyze and calculate the contribution of human activities and climate change to runoff. The results show that (1) the runoff in the Wujiang River basin has shown a decreasing trend over the years, with a sudden change in 2005 and mainly two inter-annual cycles; (2) the overall hydrological change in runoff is 48%, which is a moderate change; (3) The changes in FDC ecological indicators are significantly correlated with rainfall, and the correlation between FDC ecological indicators and IHA hydrological indicators is strong; (4) human activities are the main influencing factors of runoff changes in the Wujiang River. The results of this paper have some reference value for the management of the Wujiang River basin and the improvement and restoration of river ecology. [ABSTRACT FROM AUTHOR]

In response to growing concern about the increased disconnect between youth and their outdoor environment, this study examines how nature-based citizen science experiences with a local animal (American eels) influence urban adolescents' (high-school students) sense of place in a US city. The juvenile American eel is a unique animal due to its see-through body, small size, lengthy migratory pathway, high periodic population density, and conservation concern. Interview, written, and observational data were collected through a case study of ten high-school students during a citizen science project that lasted three months. Analyses of these data indicate that students developed greater -ecological place meaning and place attachment. Students developed greater ecological place meaning by learning more about the ecology of the river and the eels, and developed greater place attachment by developing pride and empathy. Based on these findings, we argue that nature-based citizen science programs can help environmental educators in the US foster more equitable access to nature by providing urban youth with much-needed opportunities to deeply experience local places and develop a closer and more meaningful relationship with their local environment. [ABSTRACT FROM AUTHOR]

Intermittent streams that cease to flow during dry periods represent more than half of the global river network, and are particularly common in arid and semi‐arid regions. They are characterised by high spatial and temporal variability in aquatic habitat, forming a shifting habitat mosaic that supports diverse assemblages of native and endemic species. Climate projections for much of the world predict greater variation in precipitation and increasing drought severity, suggesting a need to better understand species' responses to habitat variability within intermittent stream ecosystems. Here we explored changes in the distribution and abundance of aquatic vertebrates in response to a wide range of annual hydrologic conditions within a Mediterranean‐climate intermittent stream in California.We conducted wetted habitat and vertebrate abundance surveys during the dry season for 7 years, spanning both extreme wet and extreme dry annual precipitation conditions, and characterised the variation in the size, persistence, and spatial configuration of wetted habitats in relation to the observed abundance and composition of fishes, amphibians, and aquatic reptiles. We characterised the habitat mosaic using a k‐means clustering approach, and identified three habitat types with distinct size, persistence, and connectivity distributions.We found that some wetted habitat units persisted across all years, regardless of antecedent precipitation, whereas others dried in all but the wettest years. We determined that persistent pools, a subset of wetted habitats present in the stream, supported diverse assemblages of native species even during extreme dry conditions, while transient pools acted as important habitat for particular species and life stages, including a young‐of‐year minnow species. Linear mixed models indicated that species' abundances were influenced by habitat quantity, quality, and connectivity.Our study ‐ considers intermittent streams as shifting habitat mosaics and uses multi‐year surveys to understand the ecological consequences of habitat variability within and across years to advance our understanding of intermittent stream ecology and the implications of climate change for spatial and temporal patterns of refuge habitat. [ABSTRACT FROM AUTHOR]

Digital logistics techniques are important for business applications that contribute to economic growth. The modern supply chain or logistics seeks to implement a large-scale smart infrastructure incorporating data, physical objects, information, products, and business progressions. The business applications are utilized various intelligent techniques to maximize the logistic process. However, the logistic process suffers due to transportation costs, quality, and multinational transportation. These factors frequently affect the region's economic growth. In addition, most cities are located in remote areas that receive improper logistic support, which minimizes business growth. So, this work analyzes the impact of digital logistics on the region's economy. The Yangtze River economic belt region, which includes almost 11 cities, is chosen for analysis. The gathered information is processed by Dynamic Stochastic Equilibrium with Statistical Analysis Modelling (DSE-SAM), which predicts the correlation and influence of digital logistics on economic development. Here, the judgment matrix is constructed to reduce the difficulties of data standardization and normalization processes. Then entropy model and statistical correlation analysis are utilized to improve the overall impact analysis process. Finally, the developed DSE-SAM based created system efficiency is compared with the other economic models, such as Spatial Durbin Model (SDM), Coupling Coordination Degree Model (CCDM), and Collaborative Degree Model (CDM). The results of the suggested DSE-SAM model achieve a high correlation of urbanization, logistics, and ecology in the Yangtze River economic belt region compared to other regions. [ABSTRACT FROM AUTHOR]

Rivers are efficient corridors for aquatic animals, primarily under the assumption of perennial flow. However, the recognition that river drying is a common and widespread phenomenon requires reexamining animal movement through river networks. Intermittent rivers and ephemeral streams have been overlooked when studying animal movement, even though approximately 60% of the global river network dries. In the present article, we extend the current focus of river ecology by integrating the effects of drying on the movement of aquatic and terrestrial animals. Moreover, we introduce a conceptual model that challenges the current bias, which is focused on perennial waterways, by encompassing animal movement across hydrologic phases (nonflowing, flowing, dry, rewetting) and habitats (aquatic, terrestrial). We discuss their corridor function in conservation and restoration planning and identify emerging research questions. We contend that a more comprehensive and inclusive view of animal movement in dry channels will advance ecological understanding of river networks and respective conservation efforts. [ABSTRACT FROM AUTHOR]

Fish traps and fish weirs built by Indigenous people in the Barwon‐Darling River system of the Murray Darling Basin (MDB), south‐eastern Australia, are an important component of their traditional social, spiritual and economic systems. The celebrated Brewarrina stone fish traps (Ngunnhu) on the Barwon River are the largest and best documented stone fish traps in the Basin. However, there has been minimal research on the many other stone fish traps in this system. This paper focusses on the in‐stream stone fish traps downstream of Brewarrina along the Darling (Baaka) River, some still partly extant, remembered, or documented in historical material. Wooden and earthen bank fish traps and weirs, while not as enduring and archaeologically visible as stone fish traps, were frequently used on the Darling (Baaka) floodplain lakes, swamps and billabongs. Archaeological evidence, traditional cultural knowledge and historical materials are utilised to document the complex social processes and modification of landscapes associated with fish traps and weirs. By demonstrating that Barkandji were active and successful managers of the river and its ecology prior to colonisation, and that much of this cultural knowledge is retained by current generations, the authors make a case for them to renew their custodianship and a decision‐making role in water management. [ABSTRACT FROM AUTHOR]

Sample fixation and preservation are crucial steps for biological research. This is especially true for resolving ecological changes across various spatial and temporal scales based on sediment and/or macrozoobenthos samples, recognized to be efficient indicators of habitat quality and ecosystem health in aquatic environments. Thus, it is very important to find a convenient method for long-term sample storage. In this study, we compared effectiveness of five different solutions (glyoxal, 3.6% formaldehyde, NBF, 70% ethanol, 99% ethanol) for the preservation of macroinvertebrate taxa commonly found in stream habitats (i.e. families of aquatic insects, Chironomidae, Baetidae, Ephemeridae, Heptageniidae), with the aim to find a new "gold standard" fixative that could replace formalin, recognized to have significantly adverse health effects if exposed to it. To estimate the effectiveness of these solutions on all macrozoobenthos samples/taxa, color contrast and tissue preservation within hematoxylin and eosin stained slides were assessed as well as the preservation of body parts and tissues of collected specimens. Our results show that different preservatives/fixatives yield different effects on the tissue preservation of different organisms. None of the tested preservation liquids prove to be unique formalin successor that could serve as a new "gold standard" for preserving macroinvertebrate taxa commonly found in morphological and stream ecology studies. The efficiency of different solutions in preserving macroinvertebrate tissue integrity depends on the chemical properties and concentrations of the solutions for sample storage, tissue type as well as on the dimensions and structure (e.g., the extent of chitin coverage) of the studied organisms. [ABSTRACT FROM AUTHOR]

A longstanding challenge in stream ecology is to understand how landscape configuration organizes spatial patterns of ecosystem function via lateral groundwater connections. We combined laboratory bioassays and field additions of a metabolic tracer (resazurin) to test how groundwater‐stream confluences, or "discrete riparian inflow points" (DRIPs), regulate heterotrophic microbial activity along a boreal stream. We hypothesized that DRIPs shape spatial patterns and rates of aquatic heterotrophic microbial activity by supplying labile dissolved organic matter (DOM) to streams. Laboratory bioassays showed that the potential influence of DRIPs on heterotrophic activity varied spatially and temporally, and was related to their DOM content and composition. At the reach scale, DRIP‐stream confluences elevated the spatial heterogeneity and whole‐reach rates of heterotrophic activity, especially during periods of high land–water hydrological connectivity. Collectively, our results show how the arrangement of lateral groundwater connections influence heterotrophic activity in streams with implications for watershed biogeochemical cycles. [ABSTRACT FROM AUTHOR]

The 58th Annual Meeting of the Ichthyological Society of Japan (ISJ) will take place from September 6 to 9, 2024, at the Fukuoka Institute of Technology in Japan. The meeting will include two symposiums on river ecology and conservation of the Japanese eel, as well as the critically endangered Ryukyu-ayu Plecoglossus altivelis ryukyuensis. The event will be held in a hybrid format, and more information can be found on the ISJ official website. Additionally, the latest volume of the Japanese Journal of Ichthyology has been published, featuring various research papers. Finally, the announcement includes an obituary for Dr. Tetsuo Kuwamura, a former president of the ISJ. [Extracted from the article]

In the United States, mine reclamation has been regulated under the Surface Mining Control and Reclamation Act (SMCRA) since 1977; however, there is a lack of research examining the efficacy of this legislation on restoring ecological structure and function in affected headwater streams. We compared water chemistry characteristics, rate of senescent white oak leaf litter processing, and invertebrate community composition of three first- and second-order streams draining surface mines reclaimed in accordance with SMCRA to that of streams draining three pre-SMCRA abandoned surface mines and three unmined reference watersheds within the Western Allegheny Plateau ecoregion of Ohio. Streams draining reclaimed and abandoned mines had lower pH, higher conductivity, and leaf processing rates that averaged 7 and 24 times lower, respectively, than reference streams. The invertebrate community composition of reclaimed streams differed in several respects from abandoned mine and reference streams, including a shift in proportional dominance from leaf shredding taxa to grazing and scraping taxa, such as gastropods. Although SMCRA has successfully mitigated some sources of water quality impairment, our results suggest that mine drainage remains a persistent barrier to the restoration of headwater stream ecology in mined landscapes. [ABSTRACT FROM AUTHOR]

Most of the human population lives in cities, and understanding their impact on freshwater environments is essential. Streams in cities face many environmental challenges that have been described in the concept of Urban Stream Syndrome. This concept illustrates urban streams' biological, hydrological, chemical, and physical stressors. In tropical streams, these stressors impact shrimp, fish, insects, and other macroinvertebrates that inhabit the freshwater ecosystems. Freshwater shrimp are vulnerable to urban activities, physical, chemical, and ecological impacts. For this reason, these organisms have been used as biological indicators of stream health in the tropics. The shredder shrimp Xiphocaris elongata plays a fundamental role in the organic matter process and decomposition. The objectives of this study were to characterize the population of X. elongata and to identify differences in the abundance of X. elongata between urban and forest streams. Our results showed that highly urbanized areas have a significantly lower abundance of the shredder shrimp X. elongata than medium or low urban reach in the urban and forested watersheds. This study also showed that physicochemical and geomorphological variables are important environmental factors that influence the abundance of X. elongata in Puerto Rican streams. [ABSTRACT FROM AUTHOR]

The Odonata are not typically regarded as informative taxa for stream bioassessment in North America compared to other insects, particularly when monitoring the ecological impacts of organic pollution. However, we hypothesized that stream-dwelling odonates are useful bioindicators of riparian conditions because vegetation associated with streams is used for oviposition and establishing breeding territories and is likely a cue for a suitable nymphal habitat. We sampled odonates from multiple microhabitats and all macroinvertebrates from riffle habitat in 12 Ozark Highlands (USA) spring streams along a gradient of riparian conditions. We also measured a standard suite of physical and chemical variables in each stream. We compared various aspects of the odonate and riffle macroinvertebrate assemblages among sites to evaluate sensitivity to variables associated with riparian structure compared to the other physical and chemical variables measured. The odonates were strongly associated with riparian-specific variables, while riffle macroinvertebrates were associated with riparian variables to a lesser degree. The additional environmental variables explained minimal variation in either assemblage. Overall, our results suggest that Odonata alone could be useful for biomonitoring associated with riparian structure around Ozark spring streams. The sensitivity of odonates to riparian conditions in other Nearctic regions should be further studied to identify regional and species-specific differences. [ABSTRACT FROM AUTHOR]

Periphytic algal assemblages in the River Sindh of Kashmir Himalaya were studied in relation to environmental factors and anthropogenic alterations like flow regulation for Run-of-River hydropower plants to understand their ecology in a regulated river ecosystem. Sites were sampled from unregulated, regulated, and downstream reaches along the river on a seasonal basis from the year 2017 to 2019. A total of 48 species were identified, spread over 31 genera. Non-metric multidimensional analysis showed clear distinction in periphytic algal assemblage samples based on sites and potentially some more minor distinction based on seasons rendering the sites into two distinct groups (G1 and G2). The ADONIS test showed that the groups (G1 and G2 sites) do not significantly differ in terms of how communities differ from one another, but there is a difference in species compositions based on seasons. However, the betadisper test indicated that groups (G1 and G2 sites) and seasons present homogeneity among group dispersions (compositions vary similarly) while having significantly different compositions. Geo-physical factors (discharge and altitude) accounted for most variations, while the scraper community played a minor role. This study provides scientific insights related to the ecology of a regulated Himalayan river and may provide information relevant to managing the River Sindh sustainably. [ABSTRACT FROM AUTHOR]

Groundwater allocation in British Columbia is facing several important challenges. Groundwater is licensed under the Water Sustainability Act and potentially included in modern treaties. These challenges include acknowledging the importance of groundwater in supporting environmental flow needs and human water use, the uncertainty and misconceptions surrounding annual recharge estimates, and the under-appreciated importance of aquifer drainage, while tackling cumulative impacts in watersheds using adaptive management with clear sustainability goals. This article summarizes these challenges and suggests ways forward so that we can more robustly, holistically, and sustainably allocate groundwater resources. This includes some evidenced-based suggestions that are already being implemented partially or in some regions. Not implementing these suggestions risks permanent over-allocation of groundwater resources that would impact stream ecology, endanger rural livelihoods, and challenge reconciliation with First Nations. [ABSTRACT FROM AUTHOR]

Significant attention has been given to hyporheic water fluxes induced by hydromorphologic processes in streambeds and the effects they have on stream ecology. However, the impact of hyporheic fluxes on regional groundwater flow discharge zones as well as the interaction of these flows are much less investigated. The groundwater‐hyporheic interactive flow not only governs solute mass and heat transport in streams but also controls the retention of solute and contamination following the discharge of deep groundwater, such as naturally occurring solutes and leakage from geological waste disposal facilities. Here, we applied a physically based modeling approach combined with extensive hydrologic, geologic and geographical data to investigate the effect of hyporheic flow on groundwater discharge in the Krycklan catchment, located in a boreal landscape in Sweden. Regional groundwater modeling was conducted using COMSOL Multiphysics by considering geologic heterogeneity and infiltration constraint of the groundwater circulation intensity. Moreover, the hyporheic flow was analyzed using an exact spectral solution accounting for the fluctuating streambed topography and superimposed with the regional groundwater flow. By comparing the discharge flow fields with and without consideration of hyporheic flows, we found that the divergence of the discharge was substantially enhanced and the distribution of the travel times of groundwater was significantly shifted toward shorter times due to the presence of hyporheic flow. Particularly important is that the groundwater flow paths contract near the streambed interface due to the hyporheic flow, which leads to a phenomenon that we name "fragmentation" of coherent areas of groundwater upwelling in pinhole‐shaped stream tubes. [ABSTRACT FROM AUTHOR]

In recent years there have been growing environmental concern, especially regarding the utilisation and discharge of toxic substances. Many organic pollutants are detected in aquatic ecosystems such as pesticides. Because they are large-scale production and usage, toxicity, bioaccumulation, and persistence in the environment, they cause harmful effects to organisms and human health. The Medjerda River is one among the main rivers in Tunisia and a number of other studies addressed the importance of this river regarding ecology, geochemistry, and sociology. The organochlorine pesticides (OCPs) were investigated in surface water samples from eight sampling sites in the Medjerda River. The extraction of water samples was performed by liquid-liquid extraction with hexane. Gas chromatography coupled to the mass spectrum (GC-MS) was used to perform qualitative and quantitative determinations. The levels of OCPs in water varied between 4.41 ng g−1 and 29.04 ng g−1. The Hexachlorobenzene (HCB) and ∑DDT are the most dominant compounds in different sampling sites. Distribution of HCB, ∑DDT, and other OCPs are different indicating different sources of contamination. The concentrations of OCPs in the water pose no threat to human and aquatic living species. [ABSTRACT FROM AUTHOR]

This study analyses the heavy metal contamination in freshly deposited sediment of 210 km stretch of River Ganga between Kanpur and Prayagraj, Uttar Pradesh (U.P.), India. As per APHA (2012)30 digested samples were prepared after collecting from 10 sampling sites. Then the samples were analyzed for 8 heavy metals namely Cadmium (Cd), Chromium (Cr), Copper (Cu), Iron (Fe), Manganese (Mn), Nickel (Ni), Lead (Pb), and Zinc (Zn) by Atomic Absorption Spectroscopy (AAS) (Shimadzu AA-6300). Risk assessment was done by employing four pollution indices. The average values of contamination factor (CF) indicate that the level of contamination by Pb is moderate (1 < CF < 3) and significant by Cd (3 < CF < 6). Whereas, the average value of Geo-accumulation index (Igeo) indicates that the sediments are uncontaminated or in a moderate level of contamination by Pb (0 < Igeo < 1) and in a moderate level of contamination by Cd (1 < Igeo < 2), which may have harmful effects on Ganga River ecology. The values of Pollution load index (PLI) indicate that the Ganga River sediment has a low level of contamination. Based on various pollution indicators, it has been observed that concentrations of Cd and Pb in the river sediment is a matter of concern and may lead to further deterioration of sediment quality in near future due to increasing anthropogenic activities in the river basin, hence proper management strategies should be taken to control the direct dumping of both domestic and industrial wastewater in the river. [ABSTRACT FROM AUTHOR]

River dolphins from the genus Inia are widely distributed in the Amazon, Orinoco and Tocantins River basins. Current knowledge on the dietary habits of these species is poor and based on stomach contents from stranded animals. We used carbon and nitrogen stable isotopes to evaluate the diet preferences and trophic niche of the boto (Inia geoffrensis geoffrensis) and the bufeo (I. g. boliviensis) in three rivers from the Amazon and Tocantins basins. Samples were obtained from skin biopsies taken from social animals near fish markets during a tagging program or from dart biopsies of wild individuals. Prey isotopic data were obtained from fish collected during the surveys, catches by local fishermen or published data. Contribution of prey to consumer diet was calculated through isotope mixing models and trophic niches were represented by the isotopic niche area. Piscivore prey was the main item in the diet of bufeos and botos from Tapajós and Tocantins River wild group, whereas botos from Tocantins market group showed differences in diet and a lower trophic position probably mediated by human feeding near markets. Isotopic niche area was greater for Tapajós botos than for Tocantins market group botos and bufeos, which can be an effect of the homogenization of the human-mediated diet and low samples sizes, in the case of the market group and bufeos, respectively. Results presented here, represent a first attempt toward a better understanding of the trophic ecology of this endemic and threatened species through stable isotope analysis. [ABSTRACT FROM AUTHOR]

Gulf Stream flounder, Citharichthys arctifrons, are regularly observed in fish diets of the northeast U.S. continental shelf, yet lack commercial value and are often ignored. Similarly, Gulf Stream flounder diets of the Northwest Atlantic have remained largely unexamined, except for a brief period from 1976 to 1980. To better understand their role in the ecosystem, juvenile through adult Gulf Stream flounder were examined both as a predator and prey, and the magnitude of their feeding footprint (removal of prey biomass) was quantified for the northeast U.S. continental shelf. Their stomachs were sampled from 2005 to 2010, with the majority examined in the field macroscopically. Due to large proportions of unidentifiable prey, the effort was expanded in 2011–2012, and all stomachs were processed in the laboratory microscopically. Gulf Stream flounder were consumed by 15 fish, and what they eat (percentage mass and percentage frequency of occurrence) was documented by season, spatial region and year. Highly benthivorous, Gammaridea and Polychaeta dominated the diet in all years, seasons and regions, but Ophiuroidea (brittle stars) were also prominent in Southern New England during the spring. Gulf Stream flounder diets remained consistent across regions and time, with only a few feeding differences between seasons and one region. Relative to the productivity of benthos for this shelf ecosystem, the feeding footprint of Gulf Stream flounder was minor for their predominant benthic prey with a maximum percentage of benthos production eaten of 0.01% m−2 in Southern New England. With an ecosystem perspective, this feeding information offers a foundation for improving fisheries management among shared living marine resources considering benthic habitat and prey availability. [ABSTRACT FROM AUTHOR]

The Asian clam, Corbicula fluminea, is an invasive freshwater bivalve that has established populations across the globe and is known to have deleterious effects on natural and human systems. Yet, despite being present in the Columbia River (CR) for nearly a century, little is known about this invader's basic biology and ecology in this large river system. Thus, we undertook a field study to assess its (i) broadscale distribution and abundance, and (ii) associations with habitat characteristics in the lower CR. During 2019–2020, C. fluminea were collected from 27 shore‐based stations spanning 481 river kilometers of the lower CR, along with several habitat characteristics (bank slope, temperature, dissolved oxygen, pH, salinity, conductivity, chlorophyll‐a concentration, and sediment composition and % organic matter [OM]). C. fluminea abundance ranged from 0 to 430 ind. m−2. Most sites with abundances >100 ind. m−2 were located downstream of Bonneville Dam, whereas most sites with abundances <100 ind. m−2 were located upstream. Generalized linear models predicting the abundance of C. fluminea indicated significantly positive correlations with water temperature and % sand, and negative correlations with bank slope and sedimentary % OM. We also reviewed the global literature on abundance and habitat associations of C. fluminea and compared this with our own results. Our investigation represents the greatest spatial extent at which C. fluminea has been studied in the CR and our results provide a better understanding of the basic biology and ecology of this global invader, as well as provide natural resource managers with information on habitat conditions favorable for this invasive bivalve within temperate river ecosystems. [ABSTRACT FROM AUTHOR]

The book "Tasmanian mayflies: identification, ecology, behaviour and imitation" is a comprehensive resource on Tasmanian mayflies, covering their ecology, behavior, and importance to fly-fishers. The book includes detailed descriptions, distributions, and natural history of mayfly species found in Tasmanian waterbodies. It also discusses the decline of mayflies in certain locations and potential causes for these declines, such as hydro dam development, forestry, and climate change. The book is written in a humorous style and is relevant to both the scientific community and fly-fishers. [Extracted from the article]

As highlighted by the EU Water Framework Directive from 2000, the hydromorphology of a stream, besides water quality and biological aspects, is one of the main elements to be evaluated to correctly assess its ecological state. Notwithstanding this, there are no such studies in peninsular Southern Italy. This study provides a contribution to filling this gap by assessing the morphological quality of one of the major rivers of this area, i.e., the Calore River, by using the IDRAIM method. The latter presents the advantage of taking into account the specific Italian context in terms of channel adjustments and human pressures, together with pre-existing geomorphological approaches developed in other countries. The method is based on data obtained by means of GIS analysis, remote sensing, and field survey. The analysis provided encouraging results, highlighting the good morphological quality of the Calore River. To maintain such quality, accurate monitoring of the human activities and/or careful planning of structures that could negatively affect the river's morphological quality is unquestionably needed. The Calore River morphological quality seems to be controlled by artificiality rather than by the channel changes experienced since the 1950s. The results will be fundamental for already planned studies dealing with flood hazard and risk assessment. [ABSTRACT FROM AUTHOR]

Restoration practitioners experience mixed results when they try to engage community members in urban stream restoration projects. In some cases, practitioners make presumptions about community responses to restoration that lead to unsuccessful engagement and detract from restoration goals. During the 5th Symposium on Urbanization and Stream Ecology, we noticed that participants repeatedly discussed community stakeholder engagement as a tool for effective urban stream restoration. However, most presenters did not acknowledge that typical engagement strategies do not consider how the target community's social, economic, and political dynamics will influence stakeholder response. As a result, many practitioners make assumptions about communities that can be counterproductive to engagement efforts. Here, we discuss 4 underlying assumptions that many researchers make when trying to engage community stakeholders: 1) community members and researchers have the same project goals, 2) educating residents is essential in garnering community support, 3) the community will benefit from the restoration effort, and 4) the community has solutions to contribute to the technical aspects of the restoration effort. We present and develop these assumptions in the context of relevant urban stream restoration projects and highlight the complexity represented across communities where urban stream restoration projects can take place. Land managers and researchers must first cultivate a thoughtful understanding of the community and its existing socioeconomic capacities before integrating community stakeholders into urban stream restoration projects. We believe highlighting these societal complexities will promote a deeper consideration of appropriate engagement strategies for urban stream restoration projects. [ABSTRACT FROM AUTHOR]

Decades of research on the effects of urbanization on stream ecology have shown that urban stream problems are inherently wicked. These problems are wicked in the sense that they are difficult to solve because information is incomplete, changing, or conflicting and because finding potential solutions often requires input from stakeholders who can have conflicting and competing values. The 5th Symposium on Urbanization and Stream Ecology (SUSE5) in February 2020 brought together diverse perspectives from scientists, managers, practitioners, and local communities. Participants at SUSE5 discussed the state of the science in urban stream ecology and worked through in-depth case studies in teams to tackle complex real-world problems in urban stream management. The papers in this special series on urbanization and stream ecology include empirical research studies and synthesis papers sparked by discussions at SUSE5 and advance multidisciplinary solutions to wicked urban stream problems. [ABSTRACT FROM AUTHOR]

The threshold discharge (Q c) for streambed mobilization is both biologically and geomorphically relevant to stream ecosystems. Excess streambed mobilization can disturb benthic organisms and initiate cycles of channel instability. The mechanistic relevance of Q c gives it great utility for aquatic ecosystem studies, stormwater management, and stream restoration design. However, field and laboratory data document considerable variability in Q c across hydrogeomorphic settings, underscoring the importance of using field data to calibrate the Q c estimate for a given stream or region. This paper shows how both high- and low-tech monitoring protocols can be used to constrain a Q c estimate, depending on monitoring program goals and budgets. Data from 3 hydrogeomorphically distinct settings in the USA and Australia show that the departure of Q c from theoretical estimates increases with watershed imperviousness. Although Q c estimates derived from conventional critical Shields stress values tend to be a reasonable and conservative starting point for stormwater management in streams that lack site-specific or regional data, streambed mobility monitoring is recommended to calibrate and validate Q c estimates for a stream or region prior to making large investments in stormwater interventions aimed at mitigating the urban streambed disturbance regime. [ABSTRACT FROM AUTHOR]

Urban streams can provide amenities to people living in cities, but those benefits are reduced when streams become degraded, potentially even causing harm (disease, toxic compounds, etc.). Governments and institutions invest resources to improve the values and services provided by urban streams; however, the conception, development, and implementation of such projects may not include meaningful involvement of community members and other stakeholders. Consequently, project objectives may be misaligned with community desires and needs, and projects may fail to achieve their goals. In February 2020, the 5th Symposium on Urbanization and Stream Ecology, an interdisciplinary meeting held every 3 to 5 y, met in Austin, Texas, USA, to explore new approaches to urban stream projects, including ways to maximize the full range of potential benefits by better integrating community members into project identification and decision making. The symposium included in-depth discussion about 4 nearby field case studies, participation of multidisciplinary urban stream experts from 5 continents, and input from the Austin community. Institutional barriers to community inclusion were identified and analyzed using real-world examples, both from the case studies and from the literature, which clarified disparities in power, equity, and values. Outcomes of the symposium have been aggregated into a vision that challenges the present institutional approach to urban stream management and a set of strategies to systematically address these barriers to improve restoration solutions. Integrating community members and other stakeholders throughout the urban restoration process, and a transparent decision-making process to resolve divergent objectives, can help identify appropriate goals for realizing both the ecological and social benefits of stream restoration. [ABSTRACT FROM AUTHOR]

A major goal of community ecology is understanding the processes responsible for generating biodiversity patterns along spatial and environmental gradients. In stream ecosystems, system‐specific conceptual frameworks have dominated research describing biodiversity change along longitudinal gradients of river networks. However, support for these conceptual frameworks has been mixed, mainly applicable to specific stream ecosystems and biomes, and these frameworks have placed less emphasis on general mechanisms driving biodiversity patterns. Rethinking biodiversity patterns and processes in stream ecosystems with a focus on the overarching mechanisms common across ecosystems will provide a more holistic understanding of why biodiversity patterns vary along river networks. In this study, we apply the theory of ecological communities (TEC) conceptual framework to stream ecosystems to focus explicitly on the core ecological processes structuring communities: dispersal, speciation, niche selection, and ecological drift. Using a unique case study from high‐elevation networks of connected lakes and streams, we sampled stream invertebrate communities in the Sierra Nevada, California, USA to test established stream ecology frameworks and compared them with the TEC framework. Local diversity increased and β‐diversity decreased moving downstream from the headwaters, consistent with the river continuum concept and the small but mighty framework of mountain stream biodiversity. Local diversity was also structured by distance below upstream lakes, where diversity increased with distance below upstream lakes, in support of the serial discontinuity concept. Despite some support for the biodiversity patterns predicted from the stream ecology frameworks, no single framework was fully supported, suggesting "context dependence." By framing our results under the TEC, we found that species diversity was structured by niche selection, where local diversity was highest in environmentally favorable sites. Local diversity was also highest in sites with small community sizes, countering the predicted effects of ecological drift. Moreover, higher β‐diversity in the headwaters was influenced by dispersal and niche selection, where environmentally harsh and spatially isolated sites exhibit higher community variation. Taken together our results suggest that combining system‐specific ecological frameworks with the TEC provides a powerful approach for inferring the mechanisms driving biodiversity patterns and provides a path toward generalization of biodiversity research across ecosystems. [ABSTRACT FROM AUTHOR]

Intermittent rivers are the focus of a burgeoning subdiscipline of freshwater science, driven by mounting recognition of their ubiquity, biodiversity, and climate sensitivity. However, our understanding of their ecology is hampered by a reliance on unstandardised diversity measures, an underrepresentation of certain stream types in metacommunity research and a reticence to acknowledge biotic interactions as a potentially fundamental driver of catchment‐scale patterns in assemblage composition.This study analysed both local‐ and catchment‐scale responses of invertebrates to flow intermittence and hydrological isolation in an understudied ecosystem type (low‐gradient, groundwater‐fed headwaters). We compared responses of conventional (taxonomic richness, Shannon diversity) and more robust (coverage‐adjusted Hill–Shannon) α‐diversity metrics to drying, and analysed changes in β‐diversity components as a function of hydrological and spatial distances between samples. We also inferred the influence of biotic interactions on metacommunity structure, using hierarchical species distribution modelling to capture species‐to‐species associations after accounting for hydrological variability and dispersal traits.The conventional and robust α‐diversity metrics exhibited broadly similar shifts, although richness overestimated the decline in α‐diversity with intermittence and the Shannon index failed to detect a significant interaction between flow duration and hydrological isolation. Decomposition of β‐diversity revealed a dominance of species turnover over nestedness along the flow gradient, a finding contrary to prevailing conceptual wisdom in intermittent river ecology and one we attribute to the climatic and geological context of our study.Even after accounting for differences in hydrological niche occupation, we discovered a significant propensity for species to co‐occur with others of similar conservation status, implying that competition/colonisation trade‐offs involving rare specialists and widespread generalists could underpin metacommunity assembly in some drying headwater networks.Our results suggest that enhancing aquatic habitat connectivity in headwaters harbouring intermittent‐stream specialists could be counterproductive, and conservation plans should instead look to safeguard isolated habitats serving as biotic refuges for rare species. [ABSTRACT FROM AUTHOR]

• A model of DO transport applicable to the confluence was constructed. • The mechanism of secondary flow merger and decay at confluence was obtained. • The relationship between DO mixing and hydrodynamics at confluence was found. • The interaction of secondary flow and DO at confluence may affect the habitat there. In the natural river network, the confluences play an important role as control nodes. It is of great scientific value to study the transport and mixing process of water quality at the confluence of the mainstream and tributaries to improve the health of the river environment. In this study, dissolved oxygen (DO, the essential survival conditions for aquatic organisms) was used as a water quality index, and a 3D transport model of DO considering atmospheric reoxygenation and biodegradation oxygen consumption was constructed. The hydrodynamic mechanism of DO transport, mixing and reoxygenation at confluence under different flow ratios, junction angles and water temperature conditions was studied. The results show that the secondary flow is the main driving force of the transversal mixing at confluence, and there is a high coupling relationship between the evolution of the secondary flow and the mixing process of water quality at confluence. With the increase of flow ratio and junction angle, the intensity of secondary flow at confluence shows an exponential increase, which in turn promotes the transversal mixing efficiency of DO at confluence. The water quality of the polluted confluence under different water temperature conditions showed a trend of gradual recovery, but the higher the water temperature, the weaker the recovery rate. This study can provide theoretical support to deal with the threat to aquatic organisms caused by pollution accumulation at confluence, and provide scientific basis for the improvement of the water environment and water ecology protection in the river confluence and downstream. [ABSTRACT FROM AUTHOR]

In river deltas, human interference with regional and global socio‐ecological systems has led to a plethora of gradual and more abrupt environmental changes that result in inundation, coastal and river bank erosion, land loss and, ultimately, displaced people. Often apolitically framed as protective, state‐led transfer of people to new housing grounds, resettlement has become a common response to such displacements. In its process, existing arrangements of land tenure and occupancy and, at times more covertly, related arrangements of capital, labor and the social fabric become dislocated and reassembled. In line with emerging critical geographies of resettlement, this paper conceptualizes resettlement in river deltas against the background of environmental change as a highly political process with far‐reaching environmental, economic, social and cultural implications. For this article is based on an in‐depth review of both resettlement and political ecology literature, we first elucidate the concept of resettlement before providing a structured overview of categories and recent trends in resettlement literature. We then focus on river deltas that due to multi‐scale environmental change are about to become hotspots of future resettlement. Building on identified gaps in resettlement literature, the article concludes with opening up three analytical strands of political ecology as entry points to resettlement studies, understood as critical geographic research into localized manifestations of environmental change in river deltas. Overall, our paper aims to initialize conceptual debate, grounded in a thorough review of recent case study literature on resettlement that is informed by political ecology. The review challenges positivist reductions of resettlement processes as technocratic‐managerial tasks that so far have dominated scientific literature in this field and opens up new perspectives for critical research on resettlements in river deltas for human geographers. [ABSTRACT FROM AUTHOR]

Understanding and predicting the geographic distribution of taxa in hierarchical stream landscapes is a cornerstone of river ecology. A central issue is to tease apart the unique and shared effects of local and catchment predictors over species distributions. Here, we tested Hynes's influential hypothesis (1975, Baldi Memorial Lecture) that 'In every respect, the valley rules the stream'. We predicted that if catchment features exert a major control on in‐stream local conditions, the shared effect of local and catchment predictors should largely surpass their unique effects. To test this prediction, we used logistic regression models and variation partitioning to quantify the unique and shared effects of local and catchment predictors on the distribution of two hyporheic crustacean taxa (Bogidiellidae, Amphipoda and Anthuridae, Isopoda) in streams of New Caledonia. We sampled the two taxa at 228 sites. At each site, we quantified nine local predictors related to habitat area and stability, sediment metabolism and water origin, and eight catchment predictors related to geology, area, primary productivity, land use and specific discharge. When analyzed separately, the two predictor types explained the same amount of model variation in occurrence in both taxa. When analyzed jointly, the shared effects of the two predictor types explained twice as much model variation as the unique effect of each. The overriding contribution of shared effects was notably due to controls exerted by catchment area and geology on local habitat size and sediment metabolism, respectively. For both taxa, a model with only these two catchment predictors provided occurrence distribution as reliable as models containing only local predictors or both predictor types. Our findings pave the way for predicting reliably from catchment predictors alone the geographic distribution in local occurrence of taxa in difficult‐to‐access habitats and landscapes, such as here the hyporheic zone of tropical streams. [ABSTRACT FROM AUTHOR]