Longitudinal Connectivity Research Articles

Longitudinal functional brain connectivity maturation in premature newborn infants: modulatory influence of early music enrichment

Abstract Premature birth affects brain maturation, illustrated by altered brain functional connectivity at term equivalent age (TEA) and alters neurobehavioral outcome. To correct early developmental differences and improve neurological outcome, music during the NICU stay has been proposed as an auditory enrichment with modulatory effects on functional and structural brain development, but longitudinal effects of such interventions have not been studied so far. We longitudinally investigated resting-state functional connectivity (RS-FC) maturation in preterm infants (n=43). Data-driven Independent Component Analyses (ICA) were performed on scans obtained at 33- and 40-weeks gestational age (GA), determining the presence of distinct RSNs. Connectome analysis ´accordance measure´ quantitively examined the RS-FC both at 33- and 40-weeks GA. Further comparing the internetwork RS-FC at 33- and 40 weeks GA provided a circuitry of interest (COI) for significant maturational changes in which the effects on the RS-FC of a music intervention was tested. The connectome analyses resulted in a COI of RS-FC connections significantly maturing from 33 to 40 weeks GA, namely between the thalamic/brainstem and prefrontal-limbic, salience, sensorimotor, auditory and prefrontal cortical networks; between the prefrontal-limbic and cerebellar, visual and left hemispheric precuneus networks; between the salience and visual, and cerebellar networks; and between the sensorimotor and auditory, and posterior cingulate/precuneus networks. The infants exposed to music exhibited significantly increased maturation in RS-FC between the thalamic/brainstem and salience networks, compared to controls. This study exemplifies that preterm infant RS-FC maturation is modulated through NICU music exposure, highlighting the importance of environmental enrichment for neurodevelopment in premature newborns.

Fish community dynamics following the low-head dam removal and newly installed fish passage in a headstream tributary of Jinsha River, Southwest China

Low-head dams and small hydropower developments are widely distributed in global rivers because of their high cost-efficiency and smooth implementation. However, these installations have great ecological impacts on native fish communities due to the loss of longitudinal river connectivity. Although dam removal and fishway construction are effective measures to mitigate river fragmentation, research on their effects on fish communities remains limited to date. In this study, we investigated fish community dynamics in a mountainous tributary of the Jinsha River–Heishui River following dam removal, fishway construction, and fishway renovation. Our fish sampling data from 2018 to 2023 yielded 6137 fish belonging to 25 species, 12 families, and 3 orders. The native fish community predominantly represented the typical fish fauna of the Qinghai-Tibetan Plateau, primarily including the genus Schizothorax and the families Sisoridae and Nemacheilidae. Representative fish species in the Heishui River demonstrate notable adaptations to cold water, high altitude, and rapid flow environments. After removing the Laomuhe Dam, upstream fish abundance increased sharply, but species richness slightly decreased in the short term. Fishway construction significantly enhanced species richness and abundance and reduced the difference between the upstream and downstream fish communities from the Songxin Dam. However, the subsequent fishway renovation altered the dominance of fish species, with marginal changes in community structure and abundance. Variations in fish community dynamics in the river channel and fishway structure can be attributed to differences in ecological guilds (e.g., flow preference and thermal regime) and environmental factors (e.g., flow discharge, water temperature, and water depth). The present study provides insight into the significance of mitigation measures for the impact of dams on mountainous rivers in southwest China through ecological assessment and guides for decision-making in the conservation and restoration of specific fish communities.

Resistance of Australian fish communities to drought and flood: implications for climate change and adaptations

Climate change‐induced extreme weather and related drought and flood conditions are heterogeneous across space and time. The variability in location, timing, and magnitude of rainfall can alter how species respond to the drought and flood disturbances. To further complicate this matter, when droughts end they are often followed by extreme flooding, which are rarely considered as a disturbance (Humphries et al. 2024), let alone assessed with its own heterogeneity. Consequently, it is difficult to quantify impacts on ecological communities across large spatiotemporal scales without considering flood‐drought disturbance characteristics in sequence (Burton et al. 2020). We hypothesized that native organisms have evolved resistance to withstand repeated cycles of drought‐flood disturbances, and that established non‐native species have adapted to persist in novel conditions. To test this, we fit spatiotemporal models of species occurrence with local rainfall patterns as covariates in the drought and flood impacted Murray‐Darling basin in Australia during the decade long Millenium Drought, and its recovery period. During these drought conditions, river‐floodplain organisms in the Murray‐Darling became localized in refugia that limited longitudinal and lateral connectivity (Bond et al. 2008), and following flooding the same organisms were exposed to dispersal and recruitment opportunities (Humphries et al. 2020), as well as to hypoxic blackwater events that lead to the mortality of aquatic organisms (Small et al. 2014). At the basin‐scale we found that the range size of most native and non‐native fishes were highly resistant to the extreme drought and post‐flood conditions. At local scales, species richness, or detection, actually increased under drought conditions. Both findings highlight the resistance of species to climate change driven extreme weather, which opens new questions on community adaptations.

Multiscale morphological trajectories to support management of free-flowing rivers: the Vjosa in South-East Europe

Free-flowing rivers (FFRs) are fundamental references for river management, providing the opportunity to investigate river functioning under minimal anthropic disturbance. However, large free-flowing rivers are rare in Europe and worldwide, and knowledge of their dynamics is often scarce due to a lack of data and baseline studies. So far, their characterization is mainly grounded in the longitudinal connectivity assessment, with scarce integration of further hydro-morphological aspects, particularly concerning the processes and drivers of changes in their morphology over time scales of management relevance. This work aims to broaden the characterization of FFRs by reconstructing their catchment-scale morphological evolutionary trajectories and understanding their driving causes, to support their management better. This is achieved by integrating freely available global data including Landsat imagery and climatic reanalysis with the few locally available quantitative and qualitative information. The analysis of possible drivers of change at the catchment and reach scale assesses hydrological variability, flow regulation, land use change, sediment mining and bank protection works. We applied this approach to the Vjosa River (Albania), a model ecosystem of European significance and one of the few FFRs in Europe. The Vjosa was recently declared a Wild River National Park. We investigated its catchment-scale morphological changes over 50 years, considering four reaches of the Vjosa and four reaches of its main tributaries. Satellite imagery was analyzed taking advantage of Google Earth Engine cloud computing platform. The analysis reveals a catchment-scale response to climatic fluctuations, especially in the most natural reaches, with a significant narrowing of the active river corridor, following a flood-intense period in the early 1960s. The narrowing rate gradually decreased, from 35% before 1985 to 24% between 1985 and 2000, reaching a new equilibrium from 2000 to 2020. However, the recent trajectories of the lowland reaches have been impacted by human pressures, particularly sediment mining, which intensified after the 1990s, suggesting that these reaches may instead be far from equilibrium and adjusting to such persistent stressor. Identifying the key drivers of change and building catchment-scale knowledge of geomorphic change can inform the management of riverine protected areas, and the proposed integrated approach is a promising tool to help overcome the data scarcity typical of the limited remaining large FFRs.

Macroinvertebrate Community Responses to Disturbance in a Fragmented River With Contrasting Legacies of Alteration

ABSTRACTFlow is a critical factor determining the riverine ecosystem structure and function. Widespread hydrologic alteration, however, has impacted the ecological integrity of rivers in ways that are not well understood, including responses of biological communities to increasingly frequent and severe climatic disturbances. Our study compared the responses of invertebrate communities on woody debris to large flooding and extreme drought in two highly contrasting segments of an impaired low‐gradient river. The upstream segment, which according to previous research has higher α‐diversity and production of large‐bodied and sensitive invertebrates, maintained higher flows and longitudinal connectivity throughout the 4‐year study. Communities in this upper segment resembled one another among sites (lower spatial turnover) but experienced greater temporal shifts in composition associated with hydrological disturbances. Conversely, invertebrate communities in the highly altered downstream segment, which is impaired by reduced flow, sedimentation, and hypoxia, were composed of smaller‐bodied and pollution‐tolerant taxa with lower α‐diversity. Unlike the upper segment, communities were patchily distributed among sites (higher spatial turnover), which made it more difficult to detect system‐wide temporal variation in composition throughout the study. Our study underscores the benefit of including measures of connectivity and spatial heterogeneity when assessing the ecological integrity of lotic systems. Understanding the system‐wide response to disturbances across longer time frames can help better predict and mitigate the impacts of climate change on ecosystem integrity in degraded rivers.

Linking functional habitat and fish population dynamics modeling to improve river rehabilitation planning and assessment

In-stream habitat enhancement is widely used to improve ecological conditions in rivers, often prioritizing key fish life stages such as spawning and juvenile development. However, no standard approaches exist to predict their effects on fish recruitment and populations. Here, we use a spatially-explicit population dynamics model that integrates functional habitat dynamics to assess the impact of two rehabilitation measures in a hydropower-impacted section of the Inn River (SE Germany) on the recruitment potential of four rheophilic and lithophilic fish species — grayling, nase, barbel, and chub. Rehabilitation measures implemented included the construction of a bypass channel and an island side-channel system to improve both longitudinal connectivity and habitat conditions. In addition, we analyzed two alternatives, which would enhance functional availability of nursery habitats from actual 33.2% to 66.8% and 95.3%, respectively. The results suggest that the improved habitat conditions will yield on average additional 14.9 individuals/ha (5.6 kg/ha) of the target species. However, the limited accessibility of usable nursery habitat constitutes a significant recruitment bottleneck for all species. In the alternative scenarios, the increase of functional connectivity will result in average densities of 17.9 and 25.8 individuals/ha, respectively. However, potential further improvements are species-specific, because of distinct population responses to spawning-to-nursery habitat ratios, with density changes varying between -11.7% for grayling and +172.6% for chub. This study not only demonstrates the applicability of the modeling approach for assessing and planning rehabilitation measures but also emphasizes the importance of considering habitat ratios and their functional connectivity to optimize recruitment potential.

Integrating Habitat Suitability and Larval Drift Modeling for Spawning‐To‐Nursery Functional Habitat Connectivity Analysis in Rivers

AbstractHabitat suitability modeling is a commonly used methodology to plan and assess in‐stream habitat enhancement in rivers, such as for the key fish life stages spawning and juvenile development. However, their use only allows modeling the spatial distribution of habitats, but not their connectivity. By integrating micro‐scale habitat modeling and a larval drift model, we assess the functional connectivity between spawning and larval nursery habitats for four rheophilic and litophilic fish species in a channelized and hydropower impacted reach of the lower Inn River (Bavaria, Germany), in which two restoration measures, a bypass channel and an island side‐channel system, have been constructed to improve longitudinal connectivity and habitat conditions. The study aims to (a) map spawning and larval nursery habitats, (b) quantify their connectivity, and (c) optimize functional habitat connectivity through an alternative bypass channel location. Results show that the channel's morphological complexity influences quantity and quality of available spawning and nursery habitats and their connectivity. Despite the presence of nursery habitats across the analyzed channel, the slow lateral larval dispersion during drift limits their accessibility to only the left river bank, making only 33% of available habitats useable. The degree of functional connectivity and hence the percentage of useable habitats can however be increased up to 95.3 % when considering different spatial configurations of habitats, which were explored in two alternative restoration scenarios. The results demonstrate the importance of considering functional habitat connectivity in habitat assessments and restoration planning.

The influence of large wood on sediment routing and flow characteristics: A study in a low-order stream in the southern brazilian plateau

The coupling of sediment sources varies in terms of efficiency and availability based on the frequency and intensity patterns of rainfall events over time. It is commonly assumed that reaches with steeper gradients have higher longitudinal connectivity, while lower gradient reaches have lower longitudinal connectivity. However, considering that the longitudinal connectivity of channels is not always perfectly established, this conception regarding channel gradient may not always hold true. In forested regions, elements such as large wood can be the main agents of this disconnectivity. Thus, this study investigates the effects of large wood on sediment flux, flow characteristics and channel morphology in the context of the Atlantic Forest Biome in a low-order stream in the southern Brazilian plateau. To achieve this, measurements of hydrological variables, characterization of sediments, and channel morphology were conducted. Hydraulic and morphological variables were estimated to define hydraulic signatures for each river section. The influences of large wood barriers in the study section were highlighted through an analysis of hydraulic characteristics at different cross-sections and the assessment of morphological variables. The investigation revealed a tendency for a reduction in velocity of approximately 90 % in low-discharge conditions in sections where large wood barriers were present. In the case of high-magnitude events, the velocity reduction was considerably lower. Additionally, it was found that each large wood deposit presented uniqueness, and the structural characteristics of each reflected the potential for system disconnectivity. Finally, it was observed that both barriers have the capacity to store sediments, leading to the constriction of the cross-section due to the formation of sediment bars, although surveys revealed that fine sediments were poorly retained in both barriers.

GeoFRESH – an online platform for freshwater geospatial data processing

ABSTRACT Freshwater ecosystems are characterized by their unique longitudinal and lateral habitat connectivity. As a result, spatial units in freshwater-specific analyses can often not be considered independent of each other. Accounting for this connectivity in modelling analyses requires advanced skills in Geographic Information Systems (GIS) for adequately processing and managing the data. To address this challenge, we developed the GeoFRESH online platform, which is available at https://geofresh.org . The platform provides a graphical, easy-to-use interface to create freshwater-specific analysis-ready data for any given location in the world, based on a high-resolution stream network (https://hydrography.org/hydrography90m/hydrography90m_layers). Users can (i) upload and visualize point coordinates, (ii) automatically assign points to the closest stream network segment, (iii) annotate the point data with a suite of 104 local and/or upstream-aggregated topographic, climatic, land-cover and soil variables, (iv) visualize summary plots, and (v) download the data in csv-format for further analyses. The platform can be expanded given its modular structure and it can serve as a key element to support freshwater science and management relying on high-resolution geospatial analyses. GeoFRESH provides a low-entry interface while being complementary to the hydrographr R-package, and contributes importantly to the re-usability of data as an important aspect of the FAIR principles.

Rates of Evacuation of Bedload Sediment From an Alpine Glacier Control Proglacial Stream Morphodynamics

AbstractProglacial forefields commonly include highly dynamic fluvial systems associated with the fundamental instability between topography, flow hydraulics and sediment transport. However, there is limited knowledge of how these systems respond to changing subglacial hydrology and sediment supply. We investigated this relationship using the first continuous field‐collected data sets for both suspended and bedload sediment export and proglacial river dynamics for an Alpine glacier forefield, the Glacier d’Otemma, Switzerland. The results show a strong sensitivity of fluvial morphodynamics to the balance between sediment transport capacity and supply. When subglacial bedload export rates exceeded fluvial transport capacity, we found bar construction leading to net forefield aggradation and surficial coarsening, especially on bar heads. This intensified braiding buffered the downstream transport of coarse sediment. When subglacial bedload export rates were lower than transport capacity, incision occurred, with reduced braiding intensity, net erosion and important amounts of bedload leaving the proglacial system. We found a net fining of surficial deposits except for very isolated coarsening patterns on bar heads. Thus, proglacial forefield morphodynamics are strongly conditioned by subglacial hydrology and sediment supply, but this conditioning is also influenced by the response of the forefield itself. Proglacial forefields have an important influence on the longitudinal connectivity of sediment flux in regions sensitive to climate change, such as recently deglaciated high mountain areas. The linkages we report between subglacial processes and river morphodynamics are critical for understanding the development of embryonic forefield ecosystems.

Modelling seasonal variation of sediment connectivity and its interplay with river forms

Functional connectivity refers to the system dynamics and sediment transfer in a geomorphological system. It is usually quantified through digital elevation models of difference at two time-steps but measuring and quantifying sediment connectivity variation between the time-steps remains a challenge. In this study we utilised a combined approach of morphodynamic model and field observation for assessing seasonal spatio-temporal variation of longitudinal functional connectivity over a 6-kilometre sub-arctic river reach. Comprehensive field datasets including sediment sampling, monitoring of morphological change and continuous discharge and water level measurements, were collected multiple times during the year to calibrate and validate the model for one year. The results revealed that connectivity inside the reach is episodical and not all the morphological adjustment was tied to discharge. Connectivity varied spatio-temporally inside the reach and sediment source and sink areas could be detected. Outside of the hydrological controlled episodes, meander evolutional stage and grain size had notable role in sediment connectivity in the short-term, and therefore underlaying morphological adjustment in the long-term. This approach can contribute to enhancing already existing connectivity indices towards a functional model considering the seasonality and periodicity of connectivity in more detail and would therefore enhance river management and prediction of geomorphic systems functioning.

Population recovery of a migratory anadromous fish in a small forest stream following restoration of longitudinal connectivity

Restoration of movement corridors is a key management action used to address threats to migratory and other mobile species. Yet, we lack restoration effectiveness studies that allow for species to reestablish naturally (i.e. without supplementation) following habitat reconnection that capture all phases (dispersal, growth, and regulation) of recovery, and that takes an ecosystems approach. We investigated the natural recovery of migratory anadromous Coho salmon following habitat reconnection across a 5‐km section of Rock Creek, a forested tributary of the Cedar River, Washington, United States, 3 km upstream of Landsburg Dam. The dam blocked upstream fish movement for 102 years until the completion of a fish ladder in 2003. We also evaluated the response of non‐migratory trout, which are closely related to Coho salmon. Juvenile Coho salmon natal to the Cedar River dispersed into Rock Creek for rearing until spawning there in 2007. After restoration, juvenile Coho salmon density (fish/m2) increased 18‐fold, approaching an asymptote (i.e. regulation phase) a decade later. Coho salmon recovery in Rock Creek was spatially variable, however, slowing with distance from the site of restoration. Trout density was also higher after restoration relative to before, likely due to several mechanisms, including increased capacity resulting from the reestablishment of marine organic matter subsidies delivered by spawning anadromous fish. Our study demonstrates that migratory species can recover naturally after the restoration of habitat connectivity and associated movement corridors. Furthermore, our results suggest that such actions can also benefit nontarget species by reestablishing key ecosystem links driven by the target species.

Suitability of 2D depth-averaged simulations to support predictions of cyprinids passage through Vertical Slot Fishways

Fishways are a key measure to recover longitudinal connectivity. Among them, Vertical Slot Fishways (VSFs) have undergone extensive studies. However, very few numerical studies have included coupled hydrodynamics and ecological simulations. We investigated the impact of using three-dimensional (3D RANS) and two-dimensional (2D SWE) flow simulations in a Eulerian Lagrangian Agent-based Model (ELAM) for VSFs. Spatial distribution of turbulent kinetic energy ( k ), velocity magnitude ( | u i | ) , and velocity strain rate ( S ij ) were evaluated. While the | u i | was consistent across simulations, k was overestimated by the 2D SWE simulations. The frequency of S ij highest values was different between 3D RANS and 2D SWE. Also, the influence of these variables on the agent’s cognitive response was inconsistent. 2D SWE displayed an influence of around 0%, 35%, and 25% for k , | u i | and S ij , respectively. 3D RANS resulted in percentages of around 80% of k , 10–20% of | u i | and 0–10% of S ij . All cases were validated, demonstrating that both approaches are suitable to reproduce experimental observations. We demonstrated that the 2D SWE might serve as a good input to simulate fish movement in VSF. Nonetheless, hydrodynamic variables’ influence on agents’ decision making might be biased from real fish experience.

Influence of large wood dynamics on flow and channel morphology in a forest stream

The riparian zone is a dynamic ecosystem formed by the interaction of aquatic and terrestrial components of rivers and serves as a source of the large wood (LW). We aimed to understand the LW dynamics and the LW influence on river morphology, sediment distribution, and flow velocity within three reaches of a low-order stream. The study was performed in a segment (770 m in length) of the Perdizes stream, located in Aparados da Serra National Park, southern Brazil. We framed the study by focusing three issues: i) the processes explaining the LW dynamics in the Araucaria Forest biome; ii) the effects of LW on the flow velocity along the study reaches, and iii) the presence of LW affecting the sediment longitudinal connectivity. The methodology consisted of: (i) collection of hydrological data (rainfall, discharge, and streamflow velocity), (ii) Perdizes stream characterization by topo-bathymetric survey and river-flow simulation with HEC-RAS 5.0.7 1D. and (iii) detailed field surveys of LW and bed sediments. The LW descriptions were performed at four moments (July 10, 2019; November 19, 2019; July 24, 2020; and December 18, 2020). Abundant LW, mainly from araucaria (Araucaria angustifolia (Bertol.) Kuntze), was observed before meanders. A notable reduction in LW volume and an increased proportion of araucaria, compared to deciduous trees, were observed within the channel. Mass balance analysis indicated fluctuations in riparian vegetation biomass, emphasizing the connectivity between vegetation and the river. Streamflow velocity decreased in LW presence, from occurrence to the margin. Bed sediment diameters were consistently smaller in cross-sections with LW presence. The accumulation of smaller sediments with LW indicated partial downstream sediment disconnectivity. HEC-RAS simulations confirmed increased LW deposition in lower velocity zones. This understanding of fluvial dynamics contributes to effective natural environment management, especially in the Araucaria Forest context.

A conceptual model on the influence of logjam formation on longitudinal and lateral sediment dynamics in forested streams

Large wood (LW) and log jams have important implications for sediment dynamics within river systems. Although many case studies explore this topic, far fewer synthesize these results at the reach and basin scales. In this paper, we present a conceptual model that relates valley setting and landscape history of forested, mountain streams to spatiotemporal patterns of sediment storage and transport via the formation and decay processes of logjams. This conceptual model explores the function of logjams as sediment transport moderators, significantly influencing sediment retention, channel morphology, and lateral and longitudinal connectivity. Detailed wood inventories, channel topographic surveys, and channel morphology from four case studies are used to illustrate the range of channel responses to logjam formation, evolution, and decay in different valley contexts. Valley setting is shown to influence logjam formation and dynamics by determining the mechanisms and timing of sediment and wood recruitment. In steep and narrow (and thus coupled, confined) reaches, colluvial processes are the dominant mechanisms of wood and sediment delivery, and logjams grow vertically as sediment is stored in a wedge behind the jam (longitudinal disconnectivity). In contrast, in unconfined reaches (decoupled hillslopes), wood and sediment recruitment occurs primarily through fluvial processes, and logjams grow laterally as the channel shifts across the valley bottom. These logjams have long lifespans, often over a century, and gradually release sediment as the logjam decomposes. Sediment deposits stabilized by riparian vegetation behind these structures may persist long after logjam decay. This conceptual model is a testable framework and practical tool that offers insight into wood-sediment interaction mechanisms within steep, forested basins.

Individual activity levels and presence of conspecifics affect fish passage rates over an in‐flume barrier

AbstractDams and other in‐stream obstacles disrupt longitudinal connectivity and hinder fish from moving between habitats. Fishways and other fish passage solutions are used to pass fish over these artificial migration barriers. Fish passage functionality, however, varies greatly with fish passage design and environmental conditions and depends on fish species and characteristics. In particular, swimming performance and fish behaviour are considered key characteristics to predict fish passage performance. It is also well known, but not well quantified, that the presence of conspecifics affects fish passage behaviour. In this study, we quantified individual passage rates of PIT‐tagged gudgeons (Gobio gobio) over a scaled deep side notch weir in an hydraulic flume. We then quantified individual swimming capability (time to fatigue) and activity level (distance moved in an open field test) for the same individual fish and tested for potential effects on fish passage rate. To check for potential group effects, we then repeated the passage experiment for fish individually or in groups of five. More active fish displayed higher passage rates compared to less active fish, and fish passed the obstacle at higher rates in groups of five compared to alone. No effect of fish swimming capability on passage rates was detected. This result highlights the need to take both individual variation as well as the presence and behaviour of conspecifics into account in fish passage studies and evaluations. Doing so has the potential to improve the understanding of fish behaviour, and in the end, the design of fish passage solutions. Future studies should explore these results on free ranging fish and in relation to in‐situ fish passage solutions.

Habitat use of barbel (Barbus barbus) in a restored urban Danube tributary

Tributaries play a vital role in fish spawning and recruitment, significantly influencing mainstem river fish populations. However, in the Anthropocene era, tributaries within river networks suffered ecological degradation due to fragmentation and channelization. This has led to reduced distribution ranges and declining populations of various riverine species, underscoring the urgency of conservation and rehabilitation efforts. Our study explores the potential for reintroducing fish from the mainstem Danube River into the Wien River, an urban tributary that has undergone partial rehabilitation. We assessed habitat use and movement patterns of 20 adult barbel (Barbus barbus), a species classified as ‘near threatened’ in Austria, collected from the Danube River during the spawning season. These barbel were tagged with radio telemetry tags and relocated into the upper reaches of the Wien River, surmounting several artificial barriers in the lower sections. Although spawning activity was not observed among the barbel, possibly due to prevailing water temperatures, our data suggest that the Wien River could function as a viable temporary habitat. Barbel were notably inclined to inhabit deeper pool and run habitats. Their daily movements and home ranges were relatively limited, ranging from 0.0 to 1.1 km and 100 m to 2.9 km, respectively. One contributing factor to restricted movement was the presence of beaver and knotweed dams, which created temporary migration obstacles. On average, the barbel remained within the system for more than a month. Most of these fish migrated downstream at the onset of a significant high-flow event. Our assessment suggests that while the Wien River may not serve as a permanent habitat, it could function as a temporary habitat for migratory fish. However, to ensure accurate assessments of the restored Wien River as a spawning habitat, it is imperative to reevaluate the findings under stable spawning conditions and gather comprehensive data on relevant abiotic factors. This study advocates for the restoration of longitudinal connectivity between tributaries and mainstem rivers as a means to counteract biodiversity loss in Anthropocene river ecosystems.

Lithological controls on the timing of strath terrace staircase formation in a collisional mountain belt

AbstractIn mountain belts, strath terrace staircases serve as markers for deriving river incision rates and erosional patterns. Distinguishing between terrace patterns influenced by external perturbations like changes in climate and tectonics and those driven by internal dynamics including feedbacks between topography, erosion and sediment transport remains challenging. We demonstrate that in a collisional mountain belt, lithology can act as a first‐order control on the spatial and temporal scales of strath terrace formation. Here, we investigate the role of lithology in modulating internal dynamics and the formation of strath terraces in the Mgoun River catchment of the High Atlas in Morocco, a region characterised by constant low‐rate rock uplift, a cyclical cool‐warm/arid‐humid Quaternary climate history and contrasting bedrock lithologies. By collecting (1) modern river and terrace clast data, (2) bedrock strath and strath‐top sediment elevations of four terrace levels, (3) terrace sedimentology and (4) integration with published terrace chronology, we found a dominance of local sediment input from hillslopes, mostly from recycled bedrock conglomerates. Additionally, we found valley width, controlled by the stratigraphic and structural configuration of lithological erodibility, significantly impacts sediment connectivity. The isolation between valleys with varying widths results in varied timescales of river channel response to hillslope coupling, with hillslope‐derived stochastic sediment gravity flows preserved in fluvial terraces in some river reaches and not in others. Furthermore, asynchronous terrace formation and abandonment ages result from the low longitudinal river connectivity between multiple valleys formed in erodible rock separated by gorges in high‐strength rock. These gorges limit knickpoint migration rates, inhibiting the ability of terraces formed in one valley to spread through the catchment. These findings can inform future research distinguishing between autogenic and external signals in erosional landscapes and help carefully derive river incision rates and climate insights from terraces.

Centennial loss of lake wetlands in the Yangtze Plain, China: Impacts of land use changes accompanied by hydrological connectivity loss

Humans have played a fundamental role in altering lake wetland ecosystems, necessitating the use of diverse data types to accurately quantify long-term changes, identify potential drivers, and establish a baseline status. We complied high-resolution historical topographic maps and Landsat imagery to assess the dynamics of the lake wetlands in the Yangtze Plain over the past century, with special attention to land use and hydrological connectivity changes. Results showed an overall loss of 45.6 % (∼11,859.5 km2) of the lake wetlands over the past century. The number of lakes larger than 10 km2 decreased from 149 to 100 due to lake dispersion, vanishing, and shrinkage. The extent of lake wetland loss was 3.8 times larger during the 1930s–1970s than that in the 1970s–1990s. Thereafter, the lake wetland area remained relatively stable, and a net increase was observed during the 2010s–2020s in the Yangtze Plain. The significant loss of lake wetland was predominately driven by agricultural activities and urban land expansion, accounting for 81.1 % and 4.9 % of the total losses, respectively. In addition, the changes in longitudinal and lateral hydrological connectivity further exacerbated the lake wetland changes across the Yangtze Plain through isolation between lakes and the Yangtze River and within the lakes. A total of 130 lakes have been isolated from the Yangtze River due to the construction of sluices and dykes throughout the Yangtze Plain, resulting in the decrease in the proportion of floodplain marsh from 28.3 % in the 1930s to 8.0 % in the 2020s. Furthermore, over 260 sub-lakes larger than 1 km2 (with a total area of 1276.4 km2) are experiencing a loss of connectivity with their parent lakes currently. This study could provide an improved historical baseline of lake wetland changes to guide the conservation planning to wetland protection and prioritization area in the Yangtze Plain.

What do fish do after passing through a fishway? A radio‐telemetry study on patrimonial holobiotic species

AbstractThe restoration of longitudinal connectivity in rivers allows fish to colonise new habitats. However, there is a lack of information regarding the behaviour of fish when they colonise the newly opened river stretch. We used manual radiotelemetry to tracked individuals belonging to four species (trout, nase, grayling and barbel) after their release upstream of two obstacles in the Amblève River. We observed a diversity of movement behaviours and habitats used among the studied species. All the species used potential spawning habitats with distances travelled upstream reaching 2.4 km for the grayling, 7.0 km for the barbel, 16.9 km for the nase and 18.0 km for the trout, which also use tributaries and sub‐tributaries of the Amblève River. Post‐reproduction downstream behaviours were observed in all species, but this was made difficult by the absence of downstream migration devices at dams that forced fish to seek alternative habitats. Our study suggested that allowing fish to move upstream with fishways is beneficial as the species succeeded in reaching spawning grounds, but a holistic approach combined with the installations of devices or an opening of gates to allow post‐reproduction downstream migrations would allow them to completely accomplish their biological cycle.