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[hal-05056371] An annotated reference library for supporting DNA metabarcoding analysis of aquatic macroinvertebrates in French freshwater environments
Freshwater ecosystems are increasingly threatened by human activities, leading to biodiversity loss and ecosystem degradation. Effective biodiversity monitoring, particularly through the use of aquatic macroinvertebrates as bioindicators, is crucial for assessing ecological health. While traditional morphological methods face limitations, DNA metabarcoding offers higher accuracy and efficiency in species identification using environmental DNA. However, the success of metabarcoding is contingent on the quality of reference libraries, which are often incomplete or biased. This study aimed to construct and share a comprehensive COI-based DNA barcode library for freshwater macroinvertebrates in France, specifically targeting short gene regions amplified with fwhF2/fwhR2N primers, suitable for degraded DNA. A list of species occurring in French freshwater ecosystems was established from official national checklists and Alpine lake surveys. The resulting library was analysed for taxonomic completeness, barcode coverage and cryptic diversity. The checklist consisted of 2,841 species across 10 phyla, for which 56% had at least one COI-5P sequence available in the Barcode of Life Data System (BOLD). The analysis of cryptic diversity, based on Barcode Index Numbers (BINs) highlighted a potential high rate of cryptic diversity, although it might have been overestimated due to the wide geographic origin of the sequences. Alignment challenges with the primers were identified for certain taxa, particularly amongst Coleoptera, Diptera and Malacostraca. The genetic diversity approached by the number of haplotypes per species highlighted that most of the species have limited diversity, with only three species having more than 100 haplotypes. Finally, this study showed that a total of 57 haplotypes were shared amongst 116 distinct species. This work emphasises the need for expanded sequencing efforts to improve barcode coverage and highlighted the pitfalls associated with the use of these primers for further biodiversity assessment of macroinvertebrates with DNA.
ano.nymous@ccsd.cnrs.fr.invalid (Paula Gauvin) 05 May 2025
https://hal.inrae.fr/hal-05056371v1
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[hal-05009809] eDNA outperforms traditional methods for detecting organic pollution in a non- perennial river
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ano.nymous@ccsd.cnrs.fr.invalid (Héloïse Verdier) 28 Mar 2025
https://hal.science/hal-05009809v1
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[hal-04905434] Climate-Induced Changes in River Hydrological and Thermal Conditions in a Large Basin: Implications for Diadromous Fish Migration
Climate-induced changes in river conditions, such as water temperature and current velocity, can disrupt species migration patterns by altering the conditions encountered during migration. We assessed these impacts across the Loire River basin in Europe by compiling long-term fish passage data for three diadromous fish species at fishways, alongside reconstructed time series of water temperature and current velocity. We considered both water temperature and current velocity on days when migration was observed as ''suitable conditions'' for the species' upstream migration. Our findings for the 1963–2019 period revealed that trends in the frequency of suitable conditions for upstream migration were species-specific. For Atlantic salmon, particularly fall migrants, the frequency of suitable conditions has declined over time in certain areas. In contrast, the frequency of suitable migration conditions for both allis shad and sea lamprey has shown an overall increase across the basin. This study offers policy-makers and environmental managers valuable insights for developing effective, spatially explicit strategies to preserve diadromous fish populations amid ongoing climate change.
ano.nymous@ccsd.cnrs.fr.invalid (Hanieh Seyedhashemi) 22 Jan 2025
https://edf.hal.science/hal-04905434v1
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[hal-05057921] ATL_FISHREF: A 12S mitochondrial reference dataset for metabarcoding Atlantic fishes frequently caught during scientific surveys in the Bay of Biscay
The biodiversity crisis driven by anthropogenic pressures significantly threatens marine ecosystems. The rate of climate change and anthropogenic impacts outpace our traditional observation tools' capabilities, underscoring the urgency for new assessment methods. Environmental DNA (eDNA; DNA traces released by organisms) metabarcoding, a non‐invasive method widely developed over the last decade, represents a promising biomonitoring tool thanks to a large spatio‐temporal coverage, high detection of rare species and its time and cost‐effectiveness. However, capturing fish diversity using eDNA requires genetic reference databases, currently lacking. Improving reference databases relies on opportunistic sampling enabling the reporting of sequences for new species. The data provided here consists of barcoding 86 species of fishes over the 12S mitochondrial DNA gene. We generated 156 sequences of the mitochondrial 12S gene adapted to the “Teleo” barcodes from fishes sampled in the Bay of Biscay (BoB; Northeast Atlantic, France) between 2017 and 2019. In addition, we provided each individual the barcode details (Genbank accession number, chromatograms), a photograph, 5 ecomorphological measures and 11 life‐history traits documenting ecological functions (e.g., dispersion, habitat use, diet). Furthermore, we provided the sampling metadata (e.g., date, time, gear, coordinates, depth) and environmental variables measured in situ (e.g., conductivity, water/air temperature). This data set is valuable to improve the Northeast Atlantic eDNA genetic database, thus helping to better understand the effects of environmental forcing in the BoB, a transition zone housing mixed assemblages of boreal, temperate, and subtropical fish species susceptible to display variability in functional traits to adapt to changing conditions. The detailed Metadata for this abstract published in the Data Article section of the journal is available in MetaCat in JaLTER at https://jalter.diasjp.net/data/ERDP-2024-09 .
ano.nymous@ccsd.cnrs.fr.invalid (Romane Rozanski) 06 May 2025
https://hal.inrae.fr/hal-05057921v1
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[hal-04877601] The role of river connectivity in the distribution of fish in an anthropized watershed
The ongoing biodiversity crisis is especially severe in freshwater habitats. Anthropized watersheds, such as the Seine-Normandie basin in France, are particularly affected by human interference. The study of fish species distribution in watersheds often relies on environmental drivers such as land use or climate. Yet, fish are also exposed to river connectivity constraints, such as dams, that are understudied despite their potential impact on fish dispersal. For this study, we investigated the role of local and whole-basin longitudinal connectivity in fish distribution. We designed connectivity indices based on river network characteristics and specific mobility for 33 species and included these indices in species distribution models, taking into account habitat suitability, to quantify their role in species distribution. Keeping the best index for each species, an average of 29 % – and up to 57 % – of explained fish distribution, depending on species, was tied to connectivity. We found that high con nectivity often had a significant and positive linear effect on species presence probability. Using a scoring system across multiple indices, we found connectivity indices that took local context into account (e.g. the ecological zonation of the river) performed consistently better than others. Indices that took only dispersal limitation into account scored higher for 12 species, while barriers, alone, were the most important constraint for 10 species, the remaining 11 being associated with both. This work points to fragmentation as a cause for lower likelihood of presence for many non-diadromous river fish species. It highlights the importance of considering both physical and functional connectivity constraints in fish distribution and provides additional insights for river management and restoration.
ano.nymous@ccsd.cnrs.fr.invalid (Swann Felin) 09 Jan 2025
https://hal.science/hal-04877601v1
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[hal-04870965] Increased drying threatens alpine pond biodiversity more than temperature increase in a changing climate
Climate change is one of the main drivers of biodiversity decline. Rapidly changing climate in the form of warming, drying, and habitat isolation causes freshwater species to change their spatial extent, as most species have little capacity for in situ responses. However, the relative contribution of these three effects to freshwater species' changing spatial distributions is actively debated. To shed light on this debate, we explored temperature, hydroperiod, and habitat connectivity effects on alpine pond species occupancy probabilities in the northern French Alps. We studied alpine ponds as ideal test systems because they face climate change effects more rapidly, and in more concentrated areas, than any other freshwater ecosystem. We used multispecies occupancy models with three biological groups (amphibians, macrophytes, and Odonata) to examine contrasting responses to climate change. Contrary to expectations, temperature was not the main driver of species occupancy probabilities. Instead, hydroperiod and connectivity were stronger predictors of species occupancy probabilities. Furthermore, temperature increases had the same effect on occupancy probabilities of non-alpine specialist and alpine specialist species. Nonetheless, temperature disproportionately affected a greater number of specialist species compared with non-alpine specialists. We conclude that climate change mitigation will primarily benefit a greater number of alpine specialist species than non-alpine specialists. Finally, we suggest that enhancing our understanding of freshwater hydroperiods will improve our predictions of climate change effects on freshwater species distributions.
ano.nymous@ccsd.cnrs.fr.invalid (M. Lamouille-Hébert) 07 Jan 2025
https://hal.inrae.fr/hal-04870965v1
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[hal-04849268] Évaluation des routes de dévalaison des anguilles argentées du Rhône à travers l’aménagement hydroélectrique de Caderousse - (Compagnie Nationale du Rhône)
L’objectif de l’étude présentée ici était de mieux connaître/comprendre le cheminement des anguilles argentées en phase de dévalaison au travers de l’aménagement hydro-électrique de Caderousse ainsi que la répartition des individus entre les deux bras du delta de Camargue (Grand Rhône / Petit Rhône). L’approche mise en œuvre repose sur 4 actions : (1) capturer et marquer (implantation chirurgicale d’un émetteur acoustique) des anguilles, préalablement identifiées comme argentées (stade Durif ≥ III) en amont de l’aménagement de Caderousse (Pk214.0), (2) relâcher les individus marqués au centre de la zone de capture (Pk200.5) (3) enregistrer leur passage dans les voies de dévalaison possibles à travers l’aménagement hydroélectrique (écluse, barrage et Rhône court-circuité ou usine et canal de fuite) et (4) savoir si les individus dévalant qui arrivent en amont de la diffluence utilisent soit le Petit Rhône (Fourques- PK281.0) soit le Grand Rhône (Arles -Pk282.5) ; proxy d’une arrivée en mer Méditerranée par l’un des deux bras du delta). Pour ce faire des portes de détection composées d’un hydrophone installé sur chaque rive du Rhône permettant de détecter les émissions sonores des marques, ont été installées sur le linéaire des différentes routes de dévalaison possibles ainsi qu’en Arles et à Fourques. A noter qu’après l’aménagement de Caderousse, deux autres aménagements doivent être franchis par les anguilles avant d’arriver en Arles, l’aménagement d’Avignon (Pk233.0) et l’Aménagement de Beaucaire (Pk263.0). Les portes de détection (Pk218.0, Pk220.0 et Pk282.5) sont des passages « obligés » pour les anguilles marquées ayant entamé une dévalaison. Des tests de la qualité d’écoute des portes de détection ont montré qu’il est peu probable de ne pas entendre une marque passer par la porte. Pour mieux évaluer le comportement des anguilles entre le marquage et leur dévalaison, des campagnes de suivi mobile (télémétrie active) sont organisées pour tenter de localiser les individus marqués n’ayant pas encore dévalé. Un total de n= 234 anguilles ont été marquées (masse minimum = 600 g). N=79 anguilles ont été détectées en dévalaison, principalement la nuit. La majorité des anguilles marquées qui franchissent l’aménagement de Caderousse, n=59 utilisent la route de l’usine et n=14 la route du RCC. N=4 anguilles ont été détectées juste en amont du barrage uniquement et n=2 anguilles ont été détectées en aval de l’aménagement lors des suivis mobiles. Aucune anguille n’a été détectée dans le Petit Rhône (Fourques). Seulement n=18 anguilles sont arrivées en Arles (Grand Rhône) et 14% des anguilles détectées à l’aval de l’aménagement (Pk218) n’arrivent pas au Pk220. Un effet marquage était observé avec 7% des individus marqués qui ont dévalé au cours des 72 h après leur remise à l’eau. Les anguilles dévalaient en se déplaçant assez vite (1 à 3 m s-1 sur deux km) et 2/3 de celles qui arrivent en Arles ont mis moins de 45h (0.4 m s-1) pour parcourir 62 km dont deux aménagements. Une augmentation forte de débit et une baisse rapide de la température de l’eau semblent être un couple de facteurs environnementaux très influant. N=21 prospections mobiles ont été effectuées à l’amont et n=8 à l’aval. N=102 individus marqués ont été détectés au moins une fois au cours d’un suivi mobile et n= 64 n’ont jamais été contactés. Le nombre total d’individus par mobile à l’amont a varié de 8 à 32 ind. avec une moyenne de 21.3 ind. par prospection. Très peu d’individus ont été contactés à l’aval (entre n=2 et n=4 par prospection). Le nombre total de contacts par individu à l’amont varie de 1 à 16 (moyenne = 4.12 contacts par individu). N=36 individus n’ont été contactés qu’une seule fois, n=8 individus ont été contactés dix fois ou plus au total lors des prospections à l’amont. Par année de suivi, plus de 50 % des individus détectés en prospection de jour, l’ont été une ou deux fois au maximum et plus de 80 % l’ont été trois fois au maximum. Même si le nombre de prospections de jour a varié de 3 à 6 par année de suivi, tous les individus présents ne sont pas toujours contactés. N=68 individus ont été contactés au moins deux fois de suite et n=42 ont bougé de moins de 200 m en moyenne entre deux contacts. Les distances moyennes (resp. maximum) individuelles entre deux contacts varient de 0.04 km à 3.50 km (resp. 0.04 km à 6.64 km). Parmi les n=26 individus qui se sont beaucoup déplacé, n=16 individus ont réalisé de petits déplacements (< 550m) et n=11 individus ont réalisé au moins un grand déplacement de plus de 1.2 km. L’équipe opérationnelle de l’étude était constituée par des personnels d’INRAE, renforcés par des personnels de CNR, MRM, OFB, Fédérations de pêche locales et des pêcheurs professionnels.
ano.nymous@ccsd.cnrs.fr.invalid (Hervé Capra) 19 Dec 2024
https://hal.inrae.fr/hal-04849268v1
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[hal-04767583] Hydrological conditions determine the assembly processes of zooplankton in the largest Yangtze River-connected Lake in China
In floodplain lakes, alterations in hydrological conditions can lead to changes in the structure of aquatic communities, potentially affecting biodiversity. Despite their critical role, the influence of specific hydrological and ecological factors on zooplankton community assembly and diversity remains poorly understood. We employed various methods to clarify how aquatic communities assemble and maintain diversity in these habitats. We calculated water age with the Environmental Fluid Dynamics Code (EFDC) and identified zooplankton using environmental DNA (eDNA) technology. We used these data to explore the relationship between zooplankton assembly, water age, and other ecological factors in Poyang Lake, China's largest freshwater lake. We identified 1,142 operational taxonomic units (OTUs), mainly from Rotifera and Copepoda, representing the zooplankton community. The main driving factors for community differences were water age and total nitrogen. Water age ranged from 179 days to less than 1 day, with substantial spatial differences increasing from the western to the eastern region, particularly during the flood period (April-October). Spatial heterogeneity in other environmental factors, such as total nitrogen, dissolved organic carbon, and chlorophyll-a, also significantly impacted the zooplankton community composition. The assembly of the zooplankton community in Poyang Lake was primarily influenced by homogeneous selection, dispersal limitation, and ecological drift. During the flooding season, strong hydrodynamic forces created quick flush conditions that increased dispersal limitations, affecting the assembly process. Additionally, homogeneous selection played a major role in shaping community composition in seasonally inundated alluvial lands. This study found that water age, total nitrogen, dissolved organic carbon, and chlorophyll-a all contribute to intra-lake differences in the assembly processes of zooplankton communities in floodplain lakes. These findings improve our understanding of floodplain lake ecology, offering valuable insights for conservation biodiversity in floodplain lake.
ano.nymous@ccsd.cnrs.fr.invalid (Qingji Zhang) 05 Nov 2024
https://hal.inrae.fr/hal-04767583v1
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[hal-04815268] Patch-scale habitat dynamics: three metrics to assess ecological impacts of frequent hydropeaking
Human activities significantly alter natural river flows, impacting ecosystem functioning and biodiversity worldwide. Hydropeaking, resulting from intermittent on-demand hydropower generation, introduces sub-daily flow fluctuations exceeding natural variability. While the effects of single hydropeaking events are well-studied, the cumulative impacts of frequent hydropeaking requires further exploration. This study aims to develop metrics that captures changes in habitat dynamics at the patch scale (i.e. individual micro-habitats within the habitat mosaic) due to reoccurring hydropeaking. Using hydrodynamic simulations, we introduce three patch-scale metrics to quantify habitat dynamics with high spatial (0.5 m) and temporal (10 min) resolution: (M1) Habitat probability within patches, assessing spatio-temporal diversity of habitats; (M2) Habitat shifts within patches, evaluating habitat persistence for sessile organisms (e.g. vegetation, invertebrates); and (M3) Spatial shifts of habitats, indicating habitat relocation affecting mobile species (e.g. adult fish). Using eight hydro-morphological scenarios representing different levels of anthropogenic modification of flow and morphology, we demonstrate that these metrics effectively quantify changes in habitat dynamics at patch-scale. The results highlight the ecological relevance of these metrics and their potentially utility for river management. By identifying areas susceptible to ecological impacts, these metrics may serve as tools for hydropeaking mitigation, enabling more targeted and spatially explicit habitat management and restoration.
ano.nymous@ccsd.cnrs.fr.invalid (Nico Bätz) 02 Dec 2024
https://hal.inrae.fr/hal-04815268v1
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[hal-04776962] Ecological Vulnerability of Aquatic Ecosystems—A Review
The continuous increase of anthropogenic activities reinforces their stress on aquatic ecosystems (from continental to marine ecosystems) that are the most altered ecosystems on Earth. To evaluate the risk of ecosystem decline toward human alterations, the concept of "ecological vulnerability" was developed to help managers to prioritise conservation actions. Various definitions of vulnerability and its components were used, but this concept is often centered on the intersection of three components: sensitivity, exposition, and adaptive capacity. The aim of this study was through a review of the scientific literature of the last 10 years, first to assess the goals of the use of the concept of vulnerability in aquatic ecology: for which pressure (e.g. climate change, predation) and organism, on which level of organisation (individuals, species, …). The second objective, was to address the methods developed to assess vulnerability: which components were considered, which metrics were used, the scoring process... Fish were the organisms the most frequently concerned and the number of publications decreased with the increasing complexity of biodiversity studied (from populations to multitrophic organisations). Climate change was the main stressor for which vulnerability was assessed. Vulnerability was commonly defined as being highly sensitive, highly exposed and lowly adaptable even if adaptive capacity was rarely addressed. This study showed an interest in the concept of vulnerability to protect aquatic ecosystems. Nonetheless, to better evaluate their risk of biodiversity loss, we should consider vulnerability at a higher level of organisation and encompass the adaptive capacity of the biota.
ano.nymous@ccsd.cnrs.fr.invalid (Maxime Logez) 12 Nov 2024
https://hal.inrae.fr/hal-04776962v1
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[hal-04767911] Multidecadal trends in brown trout populations in France reveal a decline in adult abundance concomitant with environmental changes
Most studies of brown trout (Salmo trutta) populations in headwater streams have focused on the year-to-year variability in recruitment and survival, but only few analyzed long-term trends in trout densities, under both control and regulated flow conditions. Here, we conducted trend analyses of brown trout age class densities on 36 stream reaches over the 1990-2020 period, including reaches located in a bypassed section. We also investigated long-term trends in a panel of key environmental variables (water temperature, stream flow, current velocity and habitat suitability). We found that annual water temperatures significantly increased by a median of +0.21 °C per decade. Analyses of stream flow revealed only a few significant trends, including a general increase in median values in spring and a general decrease in fall. A significant general decline in adult trout densities was observed, although disparities between geographic areas were highlighted. This decline is likely due to multifactorial effects, including possible interacting factors. Our results highlight the need to maintain and extend long-term monitoring of trout populations, which should be combined with extensive environmental monitoring.
ano.nymous@ccsd.cnrs.fr.invalid (Laurence Tissot) 05 Nov 2024
https://hal.science/hal-04767911v1
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[hal-04879504] Consequences of global warming in the Rhône River on the physiology of Alburnoides bipunctatus
Nowadays, global warming is a real issue and scientists are trying to find ways to anticipate its effects on wildlife, especially ectotherms as there are the first in line to be impacted by temperature increase. Indeed, their body temperature directly depends on environmental temperature, which is a factor that drastically influences biochemical and physiological reaction rates and, in fine, body condition and behaviour. We chose to study two different populations of a pelagic fish, Alburnoides bipunctatus, that were caught mid-February 2024 upstream or downstream of the Bugey nuclear power plant, located along the Rhône River. Indeed, as the water is warmer downstream from the power plant, this river section can be regarded as a “future condition” considering global warming. So, we wondered whether downstream fish had different adaptations regarding thermal tolerance, thermal preference and swim performance compared to the upstream ones. Both populations were kept at 12°C before entering experimentation. 12 fish from each population were put through 3 experiments which were randomised in order for 3 weeks, so each fish had a week of recovery between each experiment. Our aim was to characterize the phenotypes of the two populations through different physiological and behavioural experimental protocols. We used CTmax (critical thermal maximum), which is a commonly used metric to measure an organism’s upper thermal tolerance limit and a Ucrit protocol, which is the most known method to measure swimming performance in fish and can be considered as a proxy of the fish’s general fitness and well-being. This protocol was also linked to MO2 measurement. The fish were also put in a shuttle box with dynamic temperature change to elucidate their thermal preference. We supposed that upstream fish would be in better condition than downstream ones, but that the latter would probably have a higher metabolism, higher CTmax and higher thermal preference as they live in a warmer environment. Indeed, downstream fish had a greater CTmax than upstream ones, indicating that their upper thermal limit is higher. Interestingly, both groups had a similar thermal preference but the variance among the downstream fish was high. Upstream fish had a greater Ucrit, indicating that they may be in better condition, and their metabolic rates were also higher. However, upstream fish were the smallest, so there is an effect of size on our results. Consequently, even though most of the fish are juveniles, our results could be driven by the metabolic theory of ecology.
ano.nymous@ccsd.cnrs.fr.invalid (Julia Watson) 10 Jan 2025
https://hal.science/hal-04879504v1
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[hal-04869907] RhônEco : A long term ecological observatory for monitoring the restoration of the Rhône river in a global change context
RhônEco is an interdisciplinary research program aiming at monitoring the effects of ecological restoration on the Rhône hydrosystem. Hydraulic infrastructures (e.g. hydroelectric dams) have profoundly altered the river flow, both in the main channel and the side arms, affecting both their biodiversity and their functioning. In last decades, restoring the hydrological connectivity of the Rhône lateral habitats became a priority for managers. Initiated in 1998, the RhônEco program historically focused on the assessment and the long-term monitoring of habitat and biodiversity (especially fish and macro-invertebrates) responses to restoration actions. Recently, the program evolved toward an ecological observatory of the Rhône River in a context of global change, and included new scientific questions and approaches to assess biodiversity across multiple trophic levels and characterize key ecosystem functions. A novel research axis aims at better understanding (i) the effects of restoration actions on side arms functioning, with a focus on key processes involved in carbon cycling (e.g. productivity, decomposition of organic matter, greenhouse gas emissions), and (ii) the relationships between these processes and biological communities living in these habitats. For this a multi-scalecomparative approach has been set up, including multiple side arms distributed along a connectivity gradient to the main channel.
ano.nymous@ccsd.cnrs.fr.invalid (Mathieu Tocaben) 07 Jan 2025
https://hal.science/hal-04869907v1
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[hal-04819581] Evolution des lacs glaciaires en réponse au réchauffement climatique : changement graduel ou régime shift ?
Le changement climatique constitue une menace croissante pour les écosystèmes aquatiques à travers le monde. Alors que les moyennes annuelles des températures de l’air augmentent progressivement, les réponses des écosystèmes peuvent être non linéaires, et caractérisées par des effets de seuils critiques, au-delà desquels peuvent se déclencher des transformations rapides et souvent irréversibles dans la structure et le fonctionnement des écosystèmes. Cette présentation explore l’évolution des paramètres physico-chimiques et biologiques de quatre lacs glaciaires des Alpes sur les 10 dernières années, en relation avec la dynamique des glaciers présents sur leurs bassins versants. Nous montrons que la déconnexion hydrologique entre les lacs et leurs glaciers entraîne une modification brutale du régime thermique et de la turbidité de l’eau, ainsi qu’une modification des communautés biologiques, principalement des producteurs primaires. Malgré un réchauffement atmosphérique graduel des milieux d’altitude, ces effets seuils sur le fonctionnement des écosystèmes soulignent l'importance de surveiller de près les indicateurs de stress écologique et de développer des stratégies d'adaptation robustes pour atténuer les impacts sur la ressource en eau et la biodiversité.
ano.nymous@ccsd.cnrs.fr.invalid (Florent Arthaud) 04 Dec 2024
https://hal.science/hal-04819581v1
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[hal-04739432] Environmental DNA Particle Size Distribution and Quantity Differ Across Taxa and Organelles
ABSTRACT The use of environmental DNA to detect species is now widespread in freshwater ecology. However, the detectability of species depends on many factors, such as the quantity of eDNA particles available in the environment and their state (e.g., free DNA fragments, organellar, or aggregated DNA particles). To date, the most advanced knowledge of the production and state of DNA particles concerns teleosts. Most often, these studies target mitochondrial genes, since they are present in multiple copies in a cell. However, it is likely that the characteristics of eDNA molecules vary greatly among taxa and genetic compartments, with direct consequences for species detection. Using an indoor mesocosm experiment, we compared the rate of mitochondrial and nuclear eDNA production and particle size distribution (PSD) of four distinct and common aquatic taxa (zebrafish, tadpole, isopod and mollusk). The tank water was filtered through a series of filters with decreasing porosity and mitochondrial and nuclear eDNA at each size fraction were quantified by qPCR. We found that the production and the size of eDNA particles varied greatly among taxa and genetic compartments. For most taxa, the number of nuclear eDNA particles released in water was higher than that of mitochondrial origin. The PSD of mt‐eDNA showed a pattern common to all taxa: the relative number of particles increased from the smallest size fractions (0.2 μm and less) to the largest (over 1.2 μm), while the distribution of nu‐eDNA was very different from one taxon to another. We also observed a high temporal variability in the quantity of eDNA particles and in PSD, although the latter was more complex to model. These results call for caution in how to sample and analyze eDNA in aquatic environments, particularly for organisms that emit small particles in small quantities such as isopods.
ano.nymous@ccsd.cnrs.fr.invalid (Héloïse Verdier) 16 Oct 2024
https://hal.inrae.fr/hal-04739432v1
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[hal-04879542] Consequences of climate change in the Rhône River on the swim performance and metabolism of Alburnoides bipunctatus
Nowadays, global warming is a real issue and the first in line to be impacted by temperature increase are ectotherms. Indeed, their body temperature depends on environmental temperature, which is a factor that influences biochemical and physiological reaction rates as well as body condition. We studied two different populations of a pelagic fish, Alburnoides bipunctatus, that were caught mid-February 2024 upstream or downstream the Bugey nuclear power plant, located along the Rhône River. Indeed, as the water is warmer downstream the power plant, this river section can be regarded as a “future condition” considering global warming. So, we wondered whether downstream fish had different adaptations regarding swim performance and whole-body metabolism compared to the upstream ones. Both populations were maintained at 12°C before and during experimentation. 12 fish from each group went through a Ucrit protocol, which is the most known method to measure swimming performance in fish and can be considered as a proxy of the fish’s general fitness and well-being. This allowed the measurement of SMR, MMR and aerobic scope (AS), as well as the net cost of transport for each swimming speed. We supposed that upstream fish would be in better condition than downstream ones, but that the latter would probably have a higher metabolism as they live in a warmer environment. Our results show that upstream fish have a greater Ucrit than downstream ones, indicating that they may be in better condition. Their SMR, MMR and AS are also higher, meaning that upstream fish have a greater capacity to increase their aerobic metabolic rate above maintenance levels. However, upstream fish are smaller than downstream ones, so there is an effect of size on our results. So, even though most of the fish are juveniles, our results could be driven by the metabolic theory of ecology.
ano.nymous@ccsd.cnrs.fr.invalid (Julia Watson) 10 Jan 2025
https://hal.science/hal-04879542v1
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[hal-04882065] Influence of water temperature fluctuations on the thermal preferences of Alburnoides bipunctatus in the Rhône river
[...]
ano.nymous@ccsd.cnrs.fr.invalid (Maé Fabra) 13 Jan 2025
https://hal.science/hal-04882065v1
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[hal-04699448] Une cartographie réglementaire incohérente menace les rivières et les ruisseaux Français
Même la législation environnementale la plus stricte ne peut protéger un cours d'eau si ses affluents restent exposés à la pollution et à d'autres menaces en amont. Exclure un sous-ensemble de cours d'eau de protection juridique menace donc d'altérer les écosystèmes d'eau douce de réseaux fluviaux entiers et les services qu'ils fournissent, tels que l'eau potable et la régulation des crues. Une attention considérable a été accordée à la définition du champ d'application des lois environnementales protégeant les cours d'eau. Cependant, la manière dont ces définitions sont mises en œuvre par le biais de la cartographie réglementaire, c'est-à-dire la cartographie des masses d'eau qui sont légalement considérées comme des cours d'eau et donc protégées, n'a pas été étudiée en dehors des États-Unis. Nous démontrons ici les conséquences de la cartographie réglementaire sur l'étendue des réseaux hydrographiques protégés, en utilisant la France comme étude de cas. En assemblant la première carte des cours d'eau français protégés au titre de la Loi sur l'eau, nous estimons qu'un quart des segments hydrographiques précédemment cartographiés ont été exclus, et constatons de fortes variations géographiques dans l'étendue des écosystèmes protégés. Les segments de tête de bassin et les segments non pérennes sont disproportionnellement exclus de 28% par rapport à leur prévalence (67 %) dans l'ensemble du réseau hydrographique, avec des implications potentiellement considérables pour la biodiversité et les populations humaines. Nous nous attendons à ce que les cadres réglementaires de la plupart des pays soient également sensibles à l'interprétation locale des définitions juridiques.
ano.nymous@ccsd.cnrs.fr.invalid (Mathis Loïc Messager) 16 Sep 2024
https://hal.inrae.fr/hal-04699448v1
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[hal-04750033] Biogeochemical and community ecology responses to the wetting of non-perennial streams
Transitions between dry and wet hydrologic states are the defining characteristic of non-perennial rivers and streams, which constitute the majority of the global river network. Although past work has focused on stream drying characteristics, there has been less focus on how hydrology, ecology and biogeochemistry respond and interact during stream wetting. Wetting mechanisms are highly variable and can range from dramatic floods and debris flows to gradual saturation by upwelling groundwater. This variation in wetting affects ecological and biogeochemical functions, including nutrient processing, sediment transport and the assembly of biotic communities. Here we synthesize evidence describing the hydrological mechanisms underpinning different types of wetting regimes, the associated biogeochemical and organismal responses, and the potential scientific and management implications for downstream ecosystems. This combined multidisciplinary understanding of wetting dynamics in non-perennial streams will be key to predicting and managing for the effects of climate change on non-perennial ecosystems.
ano.nymous@ccsd.cnrs.fr.invalid (Adam Nicholas Price) 23 Oct 2024
https://hal.inrae.fr/hal-04750033v1
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[hal-04700243] Inconsistent regulatory mapping quietly threatens rivers and streams
Even the most stringent environmental law cannot protect a river if its tributaries remain exposed to pollution and other threats upstream. Excluding a subset of watercourses from legal protection therefore threatens to alter freshwater ecosystems across entire river networks and the services they provide, like drinking water and flood regulation. Considerable attention has been devoted to defining the scope of environmental laws protecting watercourses. Yet how these definitions are implemented through regulatory mapping, the cartography of waterbodies that legally qualify as watercourses and are thus protected, has not been examined outside of the United States. Here, we demonstrate the consequences of regulatory mapping on the extent of river networks that are protected, using France as a case study. By assembling the first map of France’s watercourses protected under the Water Law, we estimate that a quarter of previously mapped hydrographic segments were excluded from protection, and found stark geographical variations in the extent of protected ecosystems. Headwater and non-perennial segments are disproportionately excluded by 28% compared to their prevalence (67%) in the overall hydrographic network, with potentially far-reaching implications for biodiversity and people. We expect regulatory frameworks in most countries to be equally susceptible to local interpretation of legal definitions.
ano.nymous@ccsd.cnrs.fr.invalid (Mathis Loïc Messager) 17 Sep 2024
https://hal.inrae.fr/hal-04700243v1
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[hal-04802822] Restaurer la continuité écologique des cours d’eau : que sait-on et comment passer collectivement à l’action ?
Fruit du travail d’un collectif interdisciplinaire de chercheuses et chercheurs du Réseau des Zones Ateliers, cette communication porte sur la mise en œuvre des projets de restauration de la continuité écologique des cours d’eau. Les projets de restauration se trouvent au cœur d’une importante controverse dans l’espace public français depuis plusieurs années. Nous synthétisons d’abord les effets connus de l’interruption de la continuité dans ses dimensions longitudinale, latérale et verticale vis-à-vis des enjeux biophysiques et socio-économiques. Au regard de la complexité des processus concernés, de la variabilité des contextes territoriaux possibles et des incertitudes associées à la restauration des hydrosystèmes, notre analyse révèle l’urgente nécessité de co-construire les projets de restauration dans un projet de gestion des ressources aquatiques à l’échelle d’un territoire, comprenant un processus décisionnel démocratique. La décision de restaurer ou de ne pas restaurer la continuité ne peut s’en remettre seulement à la science et à l’expertise technique. Fort de ce constat, nous proposons ainsi une démarche stratégique pour adresser les défis qui entourent la restauration de la continuité. Cette démarche intègre dix points de vigilance à prendre en compte pour la mise en œuvre de projets de restauration partagés, soutenus par les acteurs et par la population et efficaces par rapport aux objectifs définis. Nous soulignons l’importance de mener la réflexion à différentes échelles spatio-temporelles : perspective historique vs future, échelle locale vs régionale, voire nationale et internationale.
ano.nymous@ccsd.cnrs.fr.invalid (Maria Alp) 25 Nov 2024
https://hal.inrae.fr/hal-04802822v1
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[hal-04804330] Restaurer la continuité écologique des cours d’eau : que sait-on et comment passer collectivement à l’action ?
Cet article de synthèse, fruit du travail d’un collectif interdisciplinaire de chercheuses et chercheurs du Réseau des Zones Ateliers françaises (CNRS), porte sur la mise en œuvre des projets de restauration de la continuité écologique des cours d’eau. Ces projets se trouvent au cœur d’une importante controverse dans l’espace public français depuis plusieurs années. En particulier, certains acteurs questionnent la pertinence de la politique publique visant à effacer les ouvrages qui contribuent à l’interruption de la continuité des cours d’eau. Dans cet article, nous faisons d’abord une synthèse des effets connus de l’interruption de la continuité dans ses dimensions longitudinale, latérale et verticale vis-à-vis des enjeux biophysiques et socio-économiques. Eu égard à la complexité des processus concernés, de la variabilité des contextes territoriaux possibles et des incertitudes associées à la restauration des hydrosystèmes, notre analyse révèle la nécessité d’inscrire les projets de restauration dans un projet plus large autour de la gestion des ressources aquatiques mené à l’échelle d’un territoire et reposant sur un processus décisionnel participatif. La décision de restaurer ou de ne pas restaurer la continuité ne peut s’en remettre exclusivement à la science et à l’expertise technique. Forts de ce constat, nous proposons ainsi une démarche stratégique pour adresser les défis qui entourent la restauration de la continuité. Cette démarche intègre dix points de vigilance à prendre en compte pour la mise en œuvre de projets de restauration à la fois soutenus par les différents acteurs et efficaces par rapport aux objectifs définis.
ano.nymous@ccsd.cnrs.fr.invalid (Maria Alp) 26 Nov 2024
https://hal.inrae.fr/hal-04804330v1
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[hal-04686152] Warming-induced cryosphere changes predict drier Andean eco-regions
Climate change impacts on humans and ecosystems depend on the intensity, timing, and spatial variability of these changes. While considerable attention has been paid to current and future changes in temperature patterns, comparatively less attention has been devoted to water availability for humans and ecosystems. The aridity index (AI), the ratio of precipitation to potential evapotranspiration, is a common metric used to assess water availability within ecosystems. However, the role of snow in AI calculations within snowy eco-regions is often neglected, resulting in an incomplete understanding of water balance dynamics in these environments. In this study, we estimate aridification under ongoing climate change in Andean eco-regions (AEs), focusing on two horizons: 2050–2060 and 2090–2100. Using monthly TerraClimate data from 2013–2018, we calculated a mean AI for each AE, taking into account the absence of snow (pixels with a snow water equivalent (SWE) <10 mm/month) and its presence (AI-snow; pixels with a SWE>10 mm/month). We show that AI allows to differentiate the eco-regions, but that the incorporation of snow in the AI calculation highlights the heterogeneity of aridity conditions within some eco-regions with energy-limited regimes (AI >1) in the snowy zones and water-limited regimes (AI <1) elsewhere. Analysis of the CORDEX-SAM regional projections for the periods 2050–2060 and 2090–2100 indicates a general shift towards drier conditions prevailing over wetter conditions in most eco-regions, notably: the Southern Andean Steppe, the Central Andean Wet Puna, the Santa Marta Páramo, and the Peruvian Yungas. The projected reduction in snowfall in CORDEX-SAM, coupled with glacier volume loss, appears to be contributing to the prevalence of aridification across many AEs. These findings highlight potential transitions towards aridification in diverse eco-regions, with repercussions on water availability for humans and ecosystems.
ano.nymous@ccsd.cnrs.fr.invalid (Amen Al-Yaari) 03 Sep 2024
https://hal.science/hal-04686152v1
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[hal-04804308] Identifying ten critical points when implementing projects for restoration of ecological river connectivity: An interdisciplinary perspective
Projects aiming at restoration of ecological river connectivity are at the centre of an important controversy taking place in the French public arena for several years. The implementation of the national restoration policy is being put into question by several actors. Basing upon the work of an interdisciplinary group of researchers of the French Long-Term Socio-Ecological Research Network (Réseau des Zones Ateliers, CNRS), we first synthesize currently known biophysical and socioeconomic effects of connectivity interruption in its longitudinal, lateral and vertical dimensions. Spotlighting the multitude of pressures riverine ecosystems are exposed to, the variability of territorial contexts and the associated uncertainties, we insist that the decision to restore or not to restore connectivity cannot be based exclusively on science and technical expertise. The (co-)construction of a restoration project should always be inscribed within a project of water resource management at the scale of a territory and accompanied by a democratic decision-making process. We identify ten critical points to take into account at different stages of restoration project implementation in order to collectively define ecological and societal objectives, choose most appropriate restoration measures, evaluate their effects in a robust way, and importantly, achieve projects that would be supported by the stakeholders and local population in spite of the associated uncertainties. We underline the importance of considering several spatio-temporal scales within restoration projects: historical versus future perspective, local versus regional, national or international scale.
ano.nymous@ccsd.cnrs.fr.invalid (Maria Alp) 26 Nov 2024
https://hal.inrae.fr/hal-04804308v1
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[hal-04767566] Unravelling large-scale patterns and drivers of biodiversity in dry rivers
More than half of the world’s rivers dry up periodically, but our understanding of the biological communities in dry riverbeds remains limited. Specifically, the roles of dispersal, environmental filtering and biotic interactions in driving biodiversity in dry rivers are poorly understood. Here, we conduct a large-scale coordinated survey of patterns and drivers of biodiversity in dry riverbeds. We focus on eight major taxa, including microorganisms, invertebrates and plants: Algae, Archaea, Bacteria, Fungi, Protozoa, Arthropods, Nematodes and Streptophyta. We use environmental DNA metabarcoding to assess biodiversity in dry sediments collected over a 1-year period from 84 non-perennial rivers across 19 countries on four continents. Both direct factors, such as nutrient and carbon availability, and indirect factors such as climate influence the local biodiversity of most taxa. Limited resource availability and prolonged dry phases favor oligotrophic microbial taxa. Co-variation among taxa, particularly Bacteria, Fungi, Algae and Protozoa, explain more spatial variation in community composition than dispersal or environmental gradients. This finding suggests that biotic interactions or unmeasured ecological and evolutionary factors may strongly influence communities during dry phases, altering biodiversity responses to global changes.
ano.nymous@ccsd.cnrs.fr.invalid (Arnaud Foulquier) 01 Dec 2024
https://hal.inrae.fr/hal-04767566v1
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[hal-04689894] River flow intermittence influence biodiversity–stability relationships across spatial scales: Implications for an uncertain future
Abstract Climate change is increasing the proportion of river networks experiencing flow intermittence, which in turn reduces local diversity (i.e., α‐diversity) but enhances variation in species composition among sites (i.e., β‐diversity), with potential consequences on ecosystem stability. Indeed, the multiscale theory of stability proposes that regional stability can be attained not only by local processes but also by spatial asynchrony among sites. However, it is still unknown whether and how scale‐dependent changes in biodiversity associated with river flow intermittence influence stability across spatial scales. To elucidate this, we here focus on multiple metacommunities of French rivers experiencing contrasting levels of flow intermittence. We clearly show that the relative contribution of spatial asynchrony to regional stability was higher for metacommunities of intermittent than perennial rivers. Surprisingly, spatial asynchrony was mainly linked to asynchronous population dynamics among sites, but not to β‐diversity. This finding was robust for both truly aquatic macroinvertebrates and for taxa that disperse aerially during their adult stages, implying the need to conserve multiple sites across the landscape to attain regional stability in intermittent rivers. By contrast, metacommunities of truly aquatic macroinvertebrates inhabiting perennial rivers were mainly stabilized by local processes. Our study provides novel evidence that metacommunities of perennial and intermittent rivers are stabilized by contrasting processes operating at different spatial scales. We demonstrate that flow intermittence enhances spatial asynchrony among sites, thus resulting in a regional stabilizing effect on intermittent river networks. Considering that climate change is increasing the proportion of intermittent rivers worldwide, our results suggest that managers need to focus on the spatial dynamics of metacommunities more than on local‐scale processes to monitor, restore, and conserve freshwater biodiversity.
ano.nymous@ccsd.cnrs.fr.invalid (Andros Gianuca) 06 Sep 2024
https://hal.inrae.fr/hal-04689894v1
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[hal-04865678] Unfolding the dynamics of ecosystems undergoing alternating wet‐dry transitional states
Abstract A significant fraction of Earth's ecosystems undergoes periodic wet‐dry alternating transitional states. These globally distributed water‐driven transitional ecosystems, such as intermittent rivers and coastal shorelines, have traditionally been studied as two distinct entities, whereas they constitute a single, interconnected meta‐ecosystem. This has resulted in a poor conceptual and empirical understanding of water‐driven transitional ecosystems. Here, we develop a conceptual framework that places the temporal availability of water as the core driver of biodiversity and functional patterns of transitional ecosystems at the global scale. Biological covers (e.g., aquatic biofilms and biocrusts) serve as an excellent model system thriving in both aquatic and terrestrial states, where their succession underscores the intricate interplay between these two states. The duration, frequency, and rate of change of wet‐dry cycles impose distinct plausible scenarios where different types of biological covers can occur depending on their desiccation/hydration resistance traits. This implies that the distinct eco‐evolutionary potential of biological covers, represented by their trait profiles, would support different functions while maintaining similar multifunctionality levels. By embracing multiple alternating transitional states as interconnected entities, our approach can help to better understand and manage global change impacts on biodiversity and multifunctionality in water‐driven transitional ecosystems, while providing new avenues for interdisciplinary studies.
ano.nymous@ccsd.cnrs.fr.invalid (Rebeca Arias-Real) 06 Jan 2025
https://hal.inrae.fr/hal-04865678v1
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[hal-04828440] Neglected dipterans in stream studies
True flies comprise approximately one-tenth of all animal species on Earth, yet despite their prevalence and ecological significance in freshwater ecosystems, members of the insect order Diptera are frequently neglected in stream studies. This absence or inconsistency regarding Diptera in literature and taxonomic lists may leave readers with a sense of discrepancy. To illustrate this underrepresentation in quantitative ecological investigations, we conducted a targeted literature-based meta-analysis, assessing the average level of Diptera identification and the reported number of families. These findings were compared to data from 639 quantitative samples collected across six European ecoregions (Mediterranean, Alpine, Continental, Balkanic, Pannonian, Boreal) during six, bimonthly repeated sampling campaigns in 2021 and 2022. Our analysis revealed that, compared to other macroinvertebrate groups, Diptera were typically identified at a less detailed level, often only to the family level, thereby failing to fully represent Diptera diversity, especially regarding rare, less abundant families. In our review of literature studies, we identified references to a total of 40 families. Notably, Chironomidae, Ceratopogonidae, and Simuliidae were consistently represented across the majority of studies, whereas nearly half of the families were exclusively mentioned in one or two studies. No significant differences were found in the number of families across continents or various habitat types. In our case studies the number of families was significantly higher than in European stream studies, suggesting that several rare families occasionally completely neglected during sampling, sample sorting or identification. We explored potential connections among Diptera assemblages through correlation and coexistence analyses. Our results highlighted the significant influence of the more frequent Chironomidae, Ceratopogonidae, and Simuliidae on the presence or absence of other families. While correlations between Diptera families were identified, attempts to develop a predictive model for the diversity and occurrence of minor families based on the abundance of major ones proved inconclusive. For future quantitative studies on macroinvertebrate communities, it is essential to recognize, identify and incorporate less abundant Diptera families, even on family level, or in higher taxonomic resolution, if possible, to enhance understanding and prevent the loss of information concerning this compositionally and functionally uniquely diverse insect group, which represent a significant part of the entire community, and gain a better understanding on their interactions with other aquatic groups.
ano.nymous@ccsd.cnrs.fr.invalid (Bernadett Boóz) 10 Dec 2024
https://hal.science/hal-04828440v1
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[hal-04667183] Streamflow Intermittence in Europe: Estimating High‐Resolution Monthly Time Series by Downscaling of Simulated Runoff and Random Forest Modeling
Abstract Knowing where and when rivers cease to flow provides an important basis for evaluating riverine biodiversity, biogeochemistry and ecosystem services. We present a novel modeling approach to estimate monthly time series of streamflow intermittence at high spatial resolution at the continental scale. Streamflow intermittence is quantified at more than 1.5 million river reaches in Europe as the number of no‐flow days grouped into five classes (0, 1–5, 6–15, 16–29, 30–31 no‐flow days) for each month from 1981 to 2019. Daily time series of observed streamflow at 3706 gauging stations were used to train and validate a two‐step random forest modeling approach. Important predictors were derived from time series of monthly streamflow at 73 million 15 arc‐sec (∼500 m) grid cells that were computed by downscaling the 0.5 arc‐deg (∼55 km) output of the global hydrological model WaterGAP, which accounts for human water use. Of the observed perennial and non‐perennial station‐months, 97.8% and 86.4%, respectively, were correctly predicted. Interannual variations of the number of non‐perennial months at non‐perennial reaches were satisfactorily simulated, with a median Pearson correlation of 0.5. While the spatial prevalence of non‐perennial reaches is underestimated, the number of non‐perennial months is overestimated in dry regions of Europe where artificial storage abounds. Our model estimates that 3.8% of all European reach‐months and 17.2% of all reaches were non‐perennial during 1981–2019, predominantly with 30–31 no‐flow days. Although estimation uncertainty is high, our study provides, for the first time, information on the continent‐wide dynamics of non‐perennial rivers and streams.
ano.nymous@ccsd.cnrs.fr.invalid (Petra Döll) 03 Aug 2024
https://hal.science/hal-04667183v1
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[hal-04670746] The development of terrestrial ecosystems emerging after glacier retreat
The global retreat of glaciers is dramatically altering mountain and high-latitude landscapes, with new ecosystems developing from apparently barren substrates1–4. The study of these emerging ecosystems is critical to understanding how climate change interacts with microhabitat and biotic communities and determines the future of ice-free terrains1,5. Here, using a comprehensive characterization of ecosystems (soil properties, microclimate, productivity and biodiversity by environmental DNA metabarcoding6) across 46 proglacial landscapes worldwide, we found that all the environmental properties change with time since glaciers retreated, and that temperature modulates the accumulation of soil nutrients. The richness of bacteria, fungi, plants and animals increases with time since deglaciation, but their temporal patterns differ. Microorganisms colonized most rapidly in the first decades after glacier retreat, whereas most macroorganisms took longer. Increased habitat suitability, growing complexity of biotic interactions and temporal colonization all contribute to the increase in biodiversity over time. These processes also modify community composition for all the groups of organisms. Plant communities show positive links with all other biodiversity components and have a key role in ecosystem development. These unifying patterns provide new insights into the early dynamics of deglaciated terrains and highlight the need for integrated surveillance of their multiple environmental properties5.
ano.nymous@ccsd.cnrs.fr.invalid (Gentile Francesco Ficetola) 07 Nov 2024
https://hal.inrae.fr/hal-04670746v1
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[hal-04679390] Rapport scientifique du programme RhônEco (1998 – 2023)
[...]
ano.nymous@ccsd.cnrs.fr.invalid (Jean-Michel Olivier) 27 Aug 2024
https://hal.science/hal-04679390v1
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[hal-04680015] Synthèse du programme RhônEco (1998 – 2023) et recommandations
[...]
ano.nymous@ccsd.cnrs.fr.invalid (Jean-Michel Olivier) 28 Aug 2024
https://hal.science/hal-04680015v1
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[hal-04660305] Carbon emissions from inland waters may be underestimated: Evidence from European river networks fragmented by drying
Abstract River networks contribute disproportionately to the global carbon cycle. However, global estimates of carbon emissions from inland waters are based on perennial rivers, even though more than half of the world's river length is prone to drying. We quantified CO 2 and CH 4 emissions from flowing water and dry riverbeds across six European drying river networks (DRNs, 120 reaches) and three seasons and identified drivers of emissions using local and regional variables. Drivers of emissions from flowing water differed between perennial and non‐perennial reaches, both CO 2 and CH 4 emissions were controlled partly by the annual drying severity, reflecting a drying legacy effect. Upscaled CO 2 emissions for the six DRNs at the annual scale revealed that dry riverbeds contributed up to 77% of the annual emissions, calling for an urgent need to include non‐perennial rivers in global estimates of greenhouse gas emissions.
ano.nymous@ccsd.cnrs.fr.invalid (Naiara López-Rojo) 23 Jul 2024
https://hal.inrae.fr/hal-04660305v1
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[hal-04660274] The Duration of Dry Events Promotes PVC Film Fragmentation in Intermittent Rivers
The majority of microplastics (MPs) found in the environment originate from plastic fragmentation occurring in the environment and are influenced by environmental factors such as UV irradiation and biotic interactions. However, the effects of river drying on plastic fragmentation remain unknown, despite the global prevalence of watercourses experiencing flow intermittence. This study investigates, through laboratory experiments, the coupled effects of drying duration and UV irradiation on PVC film fragmentation induced by artificial mechanical abrasion. This study shows that PVC film fragmentation increases with drying duration through an increase in the abundance and size of formed MPs as well as mass loss from the initial plastic item, with significant differences for drying durations >50% of the experiment duration. The average abundance of formed MPs in treatments exposed to severe drying duration was almost two times higher than in treatments nonexposed to drying. Based on these results, we developed as a proof of concept an Intermittence-Based Plastic Fragmentation Index that may provide insights into plastic fragmentation occurring in river catchments experiencing large hydrological variability. The present study suggests that flow intermittence occurring in rivers and streams can lead to increasing plastic fragmentation, unraveling new insights into plastic pollution in freshwater systems.
ano.nymous@ccsd.cnrs.fr.invalid (Nans Barthélémy) 19 Sep 2024
https://hal.inrae.fr/hal-04660274v1
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[hal-04817332] Glaciers and Postglacial Ecosystems - Common goods to protect in the Anthropocene
The scientific community has made enormous progress in quantifying and anticipating the evolution of the Earth’s glacier volume, but a worldwide detailed analysis of the future evolution of glacierized areas and the associated ecological consequences has not yet been carried out. Thanks to detailed glacier evolution modeling, we analyzed the evolution of the 210 000 glaciers on our planet (excluding the Antarctic and Greenland ice sheets) as well as the future ice-free topography and air temperatures that will appear and prevail in deglaciated areas until 2100. Depending on the greenhouse gas emission scenarios, the world’s glaciers area of 665 000 km2 in 2020 is projected to decrease by 22 ± 8 to 49 ± 15% until 2100. As a result, areas that become ice-free between 2020 and 2100 will cover from 149,000 ± 55,000 to 339,000 ± 99,000 km2 and consist of terrestrial areas (78%) and submarine (14%) as well as terrestrial (8%) overdeepenings. This will lead to the emergence of large terrestrial (rocks and sediments, grasslands, forests, etc.), marine (fjords, lagoons, coastlines) and freshwater (lakes, wetlands, rivers) ecosystems.
ano.nymous@ccsd.cnrs.fr.invalid (Jean-Christophe Clement) 03 Dec 2024
https://hal.science/hal-04817332v1
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[hal-04865667] Time series of freshwater macroinvertebrate abundances and site characteristics of European streams and rivers
Freshwater macroinvertebrates are a diverse group and play key ecological roles, including accelerating nutrient cycling, filtering water, controlling primary producers, and providing food for predators. Their differences in tolerances and short generation times manifest in rapid community responses to change. Macroinvertebrate community composition is an indicator of water quality. In Europe, efforts to improve water quality following environmental legislation, primarily starting in the 1980s, may have driven a recovery of macroinvertebrate communities. Towards understanding temporal and spatial variation of these organisms, we compiled the TREAM dataset (Time seRies of European freshwAter Macroinvertebrates), consisting of macroinvertebrate community time series from 1,816 river and stream sites (mean length of 19.2 years and 14.9 sampling years) of 22 European countries sampled between 1968 and 2020. In total, the data include >93 million sampled individuals of 2,648 taxa from 959 genera and 212 families. These data can be used to test questions ranging from identifying drivers of the population dynamics of specific taxa to assessing the success of legislative and management restoration efforts.
ano.nymous@ccsd.cnrs.fr.invalid (Ellen Welti) 06 Jan 2025
https://hal.inrae.fr/hal-04865667v1
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[hal-04767605] Effects of different hydrological conditions on the taxonomic structure and functional traits of mollusk communities in a large floodplain wetland
Abstract Floodplain wetlands are critical to the conservation of aquatic biodiversity and the ecological integrity of river networks. However, increasing drought severity and frequency caused by climate change can reduce floodplain wetlands' resistance and recovery capacities. Mollusks, which are common inhabitants of floodplain wetlands, are among the most vulnerable species to drought. However, the response of mollusk communities to drought has received little attention. Here, we investigated how the structure and functional traits of mollusk communities changed in response to varying hydrological conditions, including a flash drought (FD) in the Poyang Lake floodplain wetland. Our findings showed that FD strongly reduced mollusk abundance and biomass, decreased both α‐ and β‐diversity, and resulted in the extinction of bivalve taxa. A sudden shift in community trait structure was discovered due to the extinction of many species. These traits, which include deposit feeding, crawling, scraping, aerial respiration, and dormancy, help mollusks survive in FD and tolerate completely dry out of their Changhuchi habitat. Finally, we discovered that dissolved oxygen was an important controlling variable for mollusk communities during drought. Our findings provide a scientific basis for the management and conservation of floodplain wetland biodiversity in the context of increasing drought frequency and intensity.
ano.nymous@ccsd.cnrs.fr.invalid (Yao Zhang) 05 Nov 2024
https://hal.inrae.fr/hal-04767605v1
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[hal-04626619] Sources, transferts, transformations dans les bassins versants : Processus, données et modélisations multi-échelles
[...]
ano.nymous@ccsd.cnrs.fr.invalid (Rémi Dupas) 27 Jun 2024
https://hal.inrae.fr/hal-04626619v1
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[hal-04626618] Reducing the carbon footprint of a research lab: how to move from individual initiatives to collective actions?
This communication aims at exposing the steps taken by a research lab – in this case INRAE RiverLy – to reduce its carbon footprint. INRAE RiverLy is an interdisciplinary research unit for the functioning of hydrosystems. The environmental transition process originates in 2020 with the creation of the RiverLy Downstream group launched to address the downstream impacts of research practices (see Vidal et al., 2023). The first step taken by the RiverLy Downstream group relates to monitoring the laboratory's carbon footprint and identifying the main emission sources. Yearly carbon accountings carried out since 2019 using the GES1.5 tool (https://apps.labos1point5.org/ges-1point5) show that purchases (equipment, consumables, etc.) account for the majority (>50%) of the lab footprint. They also highlight the impact of changes in individual practices related to business travel, with -63% of travel-related emissions in 2022 compared to 2019. A second step focused on raising awareness through a Climate Day and testing the willingness to change within our research unit through an opinion poll. Results led to writing down a lab charter which was unanimously adopted by the lab council in October 2023. This charter sets a collective 10%/year cut-down trajectory with respect to the 2022 carbon accounting, while affirming the determination to preserve the positive impact of our research on society. A third step now being undertaken by the RiverLy Downstream team is to come up with concrete collective actions to effectively reduce the lab footprint. Participatory workshops are being organised in January and February 2024 to specify agreed actions for the various research activities: long-distance travelling, purchasing scientific and IT equipment, setting up a research project, doing lab and field experiments, performing biological and chemical analyses, performing scientific computations, and organising seminars and conferences. Consolidated and agreed propositions will then be submitted to the lab council for formal acceptation and implementation. The whole process benefits from rich interactions with the INRAE national to regional strategy for reducing its environmental footprint (https://www.inrae.fr/en/corporate-social-responsibility-inrae), and with the French national initiative Labos1point5 which set up a national network of labs in transition (https://apps.labos1point5.org/transition-1point5). Vidal, J.-P., Berni, C., Coquery, M., Devers, A., Gauthier, L., Lauvernet, C., Masson, M., Mimeau, L., and Turlan, M. and the RiverLy Downstream team: How to collectively engage in reducing the carbon footprint of a research lab?, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-3462, https://doi.org/10.5194/egusphere-egu23-3462, 2023.
ano.nymous@ccsd.cnrs.fr.invalid (Claire Lauvernet) 27 Jun 2024
https://hal.inrae.fr/hal-04626618v1
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[hal-04512480] Process-based 3D groundwater flow model to simulate current and future stream intermittence in headwaters
While the role of climate conditions in controlling streamflow intermittence is well recognised, the assessment and modelling of the role of groundwater remains a challenge. In this study, we use process-based 3D groundwater flow models to simulate stream intermittency in groundwater-fed headwaters. Streamflow measurements and stream network maps are considered together to constrain the effective hydraulic properties of the aquifers. The modelling framework has been applied and validated in pilot catchments with unconfined crystalline aquifers (France) with contrasting geomorphological settings. We present the calibration framework, the analysis of uncertainties and discuss the underlying mechanisms governing the different dynamics of streamflow intermittency. The models are then used to predict streamflow intermittence under future climate scenarios. Intuitively, with decreasing recharge rates, systems with lower storage capacities lead to higher water table fluctuations, increasing the proportion of intermittent streams and reducing future perennial flows. However, the pilot sites reveal nuanced feedback mechanisms among future climate variations, groundwater recharge dynamics, and stream intermittence, where the geomorphic characteristics of the landscapes are key to regulating these feedbacks.
ano.nymous@ccsd.cnrs.fr.invalid (Ronan Abhervé) 20 Mar 2024
https://hal.science/hal-04512480v1
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[hal-04767610] The relationships between biotic uniqueness and abiotic uniqueness are context dependent across drainage basins worldwide
Abstract Context Global change, including land-use change and habitat degradation, has led to a decline in biodiversity, more so in freshwater than in terrestrial ecosystems. However, the research on freshwaters lags behind terrestrial and marine studies, highlighting the need for innovative approaches to comprehend freshwater biodiversity. Objectives We investigated patterns in the relationships between biotic uniqueness and abiotic environmental uniqueness in drainage basins worldwide. Methods We compiled high-quality data on aquatic insects (mayflies, stoneflies, and caddisflies at genus-level) from 42 drainage basins spanning four continents. Within each basin we calculated biotic uniqueness (local contribution to beta diversity, LCBD) of aquatic insect assemblages, and four types of abiotic uniqueness (local contribution to environmental heterogeneity, LCEH), categorized into upstream land cover, chemical soil properties, stream site landscape position, and climate. A mixed-effects meta-regression was performed across basins to examine variations in the strength of the LCBD-LCEH relationship in terms of latitude, human footprint, and major continental regions (the Americas versus Eurasia). Results On average, relationships between LCBD and LCEH were weak. However, the strength and direction of the relationship varied among the drainage basins. Latitude, human footprint index, or continental location did not explain significant variation in the strength of the LCBD-LCEH relationship. Conclusions We detected strong context dependence in the LCBD-LCEH relationship across the drainage basins. Varying environmental conditions and gradient lengths across drainage basins, land-use change, historical contingencies, and stochastic factors may explain these findings. This context dependence underscores the need for basin-specific management practices to protect the biodiversity of riverine systems.
ano.nymous@ccsd.cnrs.fr.invalid (Henna Snåre) 05 Nov 2024
https://hal.inrae.fr/hal-04767610v1
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[hal-04667181] Characterizing the effects of morphological microstructures and hydropeaks on fish stranding in rivers
Abstract Fish stranding in rivers, due to rapid shoreline dewatering, often occurs during the down‐ramping phase of hydropeaks, which enables peak energy production. Multiple hydropeaking characteristics and river morphology influence stranding, but little is known about the effects of riverbed microstructures. Our goal was to identify how the combination of hydropeaking characteristics and the occurrence of morphological microstructures (e.g., puddles and scour pools) influences fish stranding. For this purpose, we used an extensive dataset of fish stranding observations collected over 3 years in spring at 48 sites along a 50 km‐long reach of the Ain River, France. We aimed (1) to characterize stranding events and their associated fish assemblages and (2) to identify the spatial and temporal determinants of stranding. The occurrence of morphological microstructures was the main factor explaining fish stranding. Scour pools had a strong impact, followed by scour puddles, humid zones, and alluvial puddles. Then, hydropeaking characteristics interacted with morphology and modulated the intensity of stranding. Low flow ranges (low peak flow and low base flow) occurring after periods without hydropeaks induced ‘salmonid fry’ stranding events and ‘super‐stranding’ events (massive stranding of many taxa). Other flow ranges induced ‘regular cyprinid fry’ stranding events. Salmonids were particularly subject to stranding at the beginning of the sampling period. Recommendations are (1) to act in priority on sites where stranding is most likely, by morphological operations or by installing attractive structures in the perennial area and (2) to maintain attractive, perennial habitats in the low flow range of hydropeaks, for example, by increasing base flow.
ano.nymous@ccsd.cnrs.fr.invalid (Flora Insulaire) 03 Aug 2024
https://hal.science/hal-04667181v1
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[hal-04767619] Reviews and Syntheses: Variable Inundation Across Earth’s Terrestrial Ecosystems
Abstract. The structure, function, and dynamics of Earth’s terrestrial ecosystems are profoundly influenced by the frequency and duration that they are inundated with water. A diverse array of natural and human engineered systems experience temporally variable inundation whereby they fluctuate between inundated and non-inundated states. Variable inundation spans from extreme flooding and droughts to predictable sub-daily cycles. Variably inundated ecosystems (VIEs) include hillslopes, non-perennial streams, wetlands, floodplains, temporary ponds, tidal systems, storm-impacted coastal zones, and human engineered systems. VIEs are diverse in terms of inundation regimes, water chemistry and flow velocity, soil and sediment properties, vegetation, and many other properties. The spatial and temporal scales of variable inundation are vast, ranging from sub-meter to whole landscapes and from sub-hourly to multi-decadal. The broad range of system types and scales makes it challenging to predict the hydrology, biogeochemistry, ecology, and physical evolution of VIEs. Despite all experiencing the loss and gain of an overlying water column, VIEs are rarely considered together in conceptual, theoretical, modeling, or measurement frameworks/approaches. Studying VIEs together has the potential to generate mechanistic understanding that is transferable across a much broader range of environmental conditions, relative to knowledge generated by studying any one VIE type. We postulate that enhanced transferability will be important for predicting VIE function under future, potentially non-analog, environmental conditions. Here we aim to catalyze cross-VIE science that studies drivers and impacts of variable inundation across Earth’s VIEs. To this end, we complement expert mini-reviews of eight major VIE systems with overviews of VIE-relevant methods and challenges associated with scale. We conclude with perspectives on how cross-VIE science can derive transferable understanding via a ‘continuum approach’ in which the impacts of variable inundation are studied across multi-dimensional environmental space.
ano.nymous@ccsd.cnrs.fr.invalid (James Stegen) 05 Nov 2024
https://hal.inrae.fr/hal-04767619v1
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[hal-04619907] Recueil de projets d'expertise internationale à INRAE. Tome 2
Ce document dit "Recueil de projets d’expertise internationale" complète un premier volume édité en 2021 sur le même type d’activité (https://hal.inrae.fr/hal-04037409). Depuis la création en 2020 de la Direction Générale Déléguée à l’Expertise et l’Appui aux Politiques Publiques (DGDEAPP) il est souligné dans les échanges internes l’importance de mieux connaître, comprendre et "donner à voir" ce que recouvrent ces activités et les produits qui les caractérisent. L’Expertise-projet internationale (EPI) a été définie à travers une note de cadrage élaborée via un groupe d’experts référents. Cette note est accessible sur l’intranet de la DAPP. Au-delà de ce cadrage institutionnel, il semble important et opportun de partager les expériences concrètes, ainsi que la diversité des projets menés par les chercheurs sur cette activité. C’est le but de ce recueil que d’illustrer cette multitude de situations et d’expériences. Ainsi ce document rassemble une quarantaine de projets menés dans plus de 30 pays à travers le monde. On découvre à travers ce recueil un grand nombre d’organisations internationales commanditaires (bailleurs de l’expertise) allant de l’AFD, la FAO, le FIDA, La Banque Mondiale, l’Union Européenne (AEE, JRC), plusieurs agences onusiennes (OMS, PNUD, OMM, UNEP, GEF), l’OCDE, mais aussi des cabinets privés qui font appel à l’expertise scientifique des chercheurs de l’établissement. On y découvre également une grande diversité thématique qu’il est impossible de décrire sans en oublier mais qui vont de la sécurité sanitaire des aliments, des innovations institutionnelles pour une agriculture durable, des dispositifs d’alerte précoce pour prévenir les inondations (CREWS), la valorisation des eaux usées (REUSE), l’économie de la déforestation, les méthodes pour limiter l’impact de l’élevage (MRV), la robotique agricole, des méthodes et outils pour reconsidérer les inégalités, la pauvreté, les structures familiales etc. Si INRAE est aujourd’hui un acteur mondialement reconnu pour la réalisation de projets de recherche dimensionnant et de haut niveau, la montée en puissance des projets d’Expertise Internationale représente un nouveau vecteur de valorisation de ses savoir-faire en renforçant sa visibilité et sa notoriété.
ano.nymous@ccsd.cnrs.fr.invalid (Olga Chekhurska) 21 Jun 2024
https://hal.inrae.fr/hal-04619907v1
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[hal-04281877] Publications reveal how socio-ecological research is implemented: lessons from the Rhône Long Term Socio-Ecological Research platform
Socio-ecological research enlists inter- and transdisciplinarity to address complex environmental issues. Yet the “socio-ecological system” concept can be interpreted in many different ways. A characterization of the diverse practices in socio-ecological research could facilitate dialogue between researchers about the possible conceptual and ethical approaches. In this study, we investigated if a detailed analysis of scientific articles would reveal the nature and course of a socio-ecological research network, and the research angle of its members. The example we used was the Rhône River Long-Term Socio-Ecological Journal Pre-proof Research (LTSER) platform in France. We combined a multivariate analysis of a reading grid of publications by Rhône River LTSER researchers and a textual analysis of the scientific narratives. The publications were from a 10-year period and corresponded to those used in a recent international comparative analysis of LTSER platforms. The analysis revealed that the research was dominated by a biophysical approach, with a progressive increase in social aspects. The emergence of a transdisciplinary approach, co-constructed with operational partners, was also shown. The research conducted by the Rhône River LTSER was grounded in the context of managing a river with strong anthropic influences and interests, and the scientific approach aimed to provide knowledge for guiding decisions. Little reference was made in the publications to socio-ecological conceptual frameworks. Beyond the example of this LTSER platform, we identified indicators for describing the degree of inter- and transdisciplinarity and the different perceptions of socio-ecological systems. The narrative analysis revealed the angle of the research approach; this method could be used in future studies for a comparison of the diverse approaches of multiple research groups.
ano.nymous@ccsd.cnrs.fr.invalid (Clara Poirier) 13 Nov 2023
https://hal.science/hal-04281877v1
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[hal-04767646] Drying and fragmentation drive the dynamics of resources, consumers and ecosystem functions across aquatic‐terrestrial habitats in a river network
Rivers form meta‐ecosystems, in which disturbance and connectivity control biodiversity, ecosystem functioning and their interactions across the river network, but also across connected instream and riparian ecosystems. This aquatic–terrestrial linkage is modified by drying, a disturbance that also naturally fragments river networks and thereby modifies organism dispersal and organic matter (OM) transfers across the river network. However, little evidence of the effects of drying on river network‐scale OM cycling exists. Here, we assessed the effects of fragmentation by drying at the river meta‐ecosystem scale by monitoring leaf resource stocks, invertebrate communities and decomposition rates, across three seasons and 20 sites, in the instream and riparian habitats of a river network naturally fragmented by drying. Although instream leaf resource quantity and quality increased, leaf‐shredder invertebrate richness and abundance decreased with flow intermittence. Decomposition was, however, mainly driven by network‐scale fragmentation and connectivity. Shredder richness and invertebrate‐driven decomposition both peaked at sites with intermediate amounts of intermittent reaches upstream, suggesting that upstream drying can promote the biodiversity and functioning of downstream ecosystems. Shredder richness, however, had a negative effect on decomposition in perennial sites, likely due to interspecific competition. Leaf quantity, invertebrate communities and invertebrate‐driven decomposition became more similar between instream and riparian habitats as drying frequency increased, likely due to homogenization of environmental conditions between both habitats as the river dried. Our study demonstrates the paramount effects of drying on the dynamics of resources, communities and ecosystem functioning in rivers and presents evidence of one of the first network‐scale examples of the co‐drivers of ecosystem functions across terrestrial–aquatic boundaries.
ano.nymous@ccsd.cnrs.fr.invalid (Romain Sarremejane) 05 Nov 2024
https://hal.inrae.fr/hal-04767646v1
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[hal-04592271] River network‐scale drying impacts the spatiotemporal dynamics of greenhouse gas fluxes
Abstract Rivers significantly contribute to global biogeochemical cycles; however, we have a limited understanding of how drying may influence these cycles. Drying fragments river networks, thereby influencing important ecosystem functions such as the processing of carbon and nitrogen, and associated fluxes of greenhouse gases (GHGs) both locally, and at the river network scale. Our objective was to assess, using a network‐scale approach, the lateral, longitudinal, and temporal dynamics of GHG fluxes in a river network naturally fragmented by drying. We used a closed‐loop chamber with automated analyzers to measure carbon dioxide (CO 2 ), methane (CH 4 ), and nitrous oxide (N 2 O) fluxes from dry sediments, flowing waters, isolated pools, and riparian soils, along with a suite of environmental variables, over 9 months at 20 sites across a non‐perennial river network in France. Network‐scale drying had a spatial and temporal legacy effect on GHG fluxes. On average, CO 2 fluxes were up to 29 times higher from perennial than non‐perennial sites under flowing conditions. At non‐perennial sites, CO 2 and N 2 O fluxes positively covaried with time since rewetting. In addition, CO 2 and N 2 O fluxes at perennial sites positively covaried with the percent of non‐perennial reaches upstream, indicating a spatial effect of drying. GHG fluxes from riparian soil and dry riverbed sediments had markedly different magnitudes and covariates. This research demonstrates that drying not only has a local‐scale impact but also influences GHG fluxes at the network scale, contributing valuable insights for upscaling global riverine GHG estimates.
ano.nymous@ccsd.cnrs.fr.invalid (Teresa Silverthorn) 29 May 2024
https://hal.inrae.fr/hal-04592271v1
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[hal-04455950] Etude de l’impact des prélèvements d’eau en cours d’eau hors étiage
Cette étude contribue à cerner les impacts écohydrologiques des prélèvements de hautes eaux sur les écosystèmes aquatiques, (1) en identifiant des indicateurs écohydrologiques (c’est-à-dire des variables hydrologiques qui reflètent la qualité de l’habitat des organismes ou le fonctionnement écologique) adaptés à l’étude de ces impacts, et (2) en estimant comment ces indicateurs seraient affectés par des scénarios de prélèvements directs, en rivière. Le scénario testé reprend les règles de prélèvement proposées par le SDAGE Loire Bretagne. La variabilité naturelle saisonnière des débits constitue à la fois un moteur évolutif, un support de biodiversité et un facteur important de résilience des hydrosystèmes. Les hautes et moyennes eaux ne sont pas des eaux "excédentaires" que l'on pourrait détourner du milieu sans précautions. L'étude de la bibliographie montre cependant la difficulté de définir des indicateurs hydroécologiques généralisables. Il a toutefois été possible de distinguer certains indicateurs (de « moyennes » eaux pour le débit dépassé 10% du temps, ou de hautes eaux pour la crue de récurrence 1 ou 1.5 an). Ces indicateurs ne sont cependant pas binaires ; ils ne présentent pas de valeurs "seuils" a priori, au-delà desquelles il n'y aurait aucun impact écologique et en-deçà desquelles les impacts seraient irrémédiables. L'utilisation de ces indicateurs doit donc se faire selon une approche comparative : leur degré d'altération relatif par rapport à une situation naturelle ou naturalisée apporte des éléments utiles pour estimer les impacts potentiels de scénarios de prélèvement (à noter que cette approche comparative de scénarios alternatifs est également celle adoptée dans la définition des débits minimums). Cette approche diagnostique doit être nourrie d'une expertise locale, permettant de préciser le contexte et le fonctionnement écologique des cours d'eau considérés afin de bien appréhender les impacts potentiels des prélèvements. En appliquant les règles de prélèvement fixées par le SDAGE Loire-Bretagne sur plus de 500 stations hydrométriques, il apparaît que, sur une année « moyenne » d'un point de vue hydrologique, le volume potentiellement prélevable est assez faible au regard des écoulements annuels. Toutefois, ce prélèvement théorique (sous réserve qu'il soit nécessaire) ne pourra être mis en œuvre à n'importe quel moment. En effet, le degré d’altération des indicateurs hydrologiques définis varie en fonction des années. Cette étude montre notamment que le nombre de jours potentiels de prélèvements peut être réduit lors des années « sèches », et donc conduire à des volumes potentiellement prélevables beaucoup plus faibles Les effets attendus du changement climatique sur les débits des cours d'eau concernés devront donc également être considérés, afin que les règles mises en place soient durables. Une bonne temporalité des prélèvements doit permettre de limiter les impacts sur les milieux, mais ne doit pas créer de dépendance supplémentaire à la ressource en eau. La durabilité du partage de cette ressource entre les usages et les milieux naturels repose en grande partie sur une bonne connaissance des prélèvements à l’échelle saisonnière, ce qui n'est pas le cas aujourd'hui au niveau national.
ano.nymous@ccsd.cnrs.fr.invalid (Franck Cattanéo) 13 Feb 2024
https://hal.inrae.fr/hal-04455950v1
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[hal-04592209] Use of trait concepts and terminology in freshwater ecology: Historic, current, and future perspectives
Abstract Trait‐based approaches have received increasing interest among freshwater scientists given their capacity to predict community structure and biodiversity effects on ecosystem functioning. However, the inconsistent development and use of trait concepts and terms across freshwater scientific disciplines may have limited realisation of the potential of traits. Here, we reviewed trait definitions and terms use to provide recommendations for their consistent application in freshwater science. To do so, we first reviewed literature to identify established trait definitions, historical and current use of trait terms and challenges restricting the application of trait‐based approaches in freshwater science. Next, we surveyed 414 freshwater researchers from 54 countries to assess variability in the current use of trait terminology in relation to respondent characteristics (i.e., professional experience, geographical region, research discipline, and focal freshwater ecosystem, biotic group, and ecosystem function). Our literature review identified two well‐established trait definitions, which emphasise individual phenotypic characteristics that influence either eco‐evolutionary aspects (i.e., organism performance and fitness) or ecosystem dynamics and processes (i.e., responses to the environment and/or effects on ecosystem functioning). Publications used a range of trait‐related terms and their frequency of use varied among scientific fields. The term functional trait dominated fields such as biodiversity conservation, environmental sciences and ecology, plant sciences and microbiology. In contrast, the terms biological trait , functional trait , and species trait were used with similar frequencies in fields such as entomology, fisheries, marine and freshwater biology, and zoology. We also found that well‐established trait definitions are difficult to apply to freshwater unicellular organisms, colonial multicellular organisms, genomic information, and cultural traits. Our survey revealed highly inconsistent use of trait terms among freshwater researchers. Terms including biological trait , functional trait , structural measure , and ecosystem function were commonly used to describe the same traits or functions. Variability in the use of terms was generally explained by research discipline, geographical region, and focal biotic group and ecosystem functions. We propose making the trait concept flexible enough to be applicable to all freshwater biota and their characteristics, while keeping and integrating links to eco‐evolutionary and ecosystem aspects. Specifically, our new definition expands the established functional trait definition by considering also supra‐individual scales of trait measurement (colonial‐ or community‐mean traits), genotypic traits (e.g., functional gene markers of enzymes) and cultural traits (e.g., feeding behaviours, communication skills). To reduce terminological ambiguity, we also recommend that researchers define trait terms, prioritising the use of functional trait as an overarching term over alternative terms (e.g., biological trait ), and restricting specific terms (e.g., morphological trait ) to situations in which such precision is desirable. The findings of our integrative study could help to improve terminological consistency across freshwater disciplines and to better recognise the potential of traits to elucidate the mechanisms behind ecological patterns.
ano.nymous@ccsd.cnrs.fr.invalid (Cayetano Gutiérrez‐cánovas) 29 May 2024
https://hal.inrae.fr/hal-04592209v1
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[hal-04767630] Towards (better) fluvial meta-ecosystem ecology: a research perspective
Abstract Rivers are an important component of the global carbon cycle and contribute to atmospheric carbon exchange disproportionately to their total surface area. Largely, this is because rivers efficiently mobilize, transport and metabolize terrigenous organic matter (OM). Notably, our knowledge about the magnitude of globally relevant carbon fluxes strongly contrasts with our lack of understanding of the underlying processes that transform OM. Ultimately, OM processing en route to the oceans results from a diverse assemblage of consumers interacting with an equally diverse pool of resources in a spatially complex network of heterogeneous riverine habitats. To understand this interaction between consumers and OM, we must therefore account for spatial configuration, connectivity, and landscape context at scales ranging from local ecosystems to entire networks. Building such a spatially explicit framework of fluvial OM processing across scales may also help us to better predict poorly understood anthropogenic impacts on fluvial carbon cycling, for instance human-induced fragmentation and changes to flow regimes, including intermittence. Moreover, this framework must also account for the current unprecedented human-driven loss of biodiversity. This loss is at least partly due to mechanisms operating across spatial scales, such as interference with migration and habitat homogenization, and comes with largely unknown functional consequences. We advocate here for a comprehensive framework for fluvial networks connecting two spatially aware but disparate lines of research on (i) riverine metacommunities and biodiversity, and (ii) the biogeochemistry of rivers and their contribution to the global carbon cycle. We argue for a research agenda focusing on the regional scale—that is, of the entire river network—to enable a deeper mechanistic understanding of naturally arising biodiversity–ecosystem functioning coupling as a major driver of biogeochemically relevant riverine carbon fluxes.
ano.nymous@ccsd.cnrs.fr.invalid (Lauren Talluto) 05 Nov 2024
https://hal.inrae.fr/hal-04767630v1
