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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-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-04679390] Rapport scientifique du programme RhônEco (1998 – 2023)
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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-04626619] Sources, transferts, transformations dans les bassins versants : Processus, données et modélisations multi-échelles
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ano.nymous@ccsd.cnrs.fr.invalid (Rémi Dupas) 27 Jun 2024
https://hal.inrae.fr/hal-04626619v1
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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-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-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-04343848] Meroplanktic phytoplankton play a crucial role in responding to peak discharge events in the middle lowland section of the Loire River (France)
Meteorological and hydrological forcings influence phytoplankton at very short time scales. The effect of turbulence, dilution, light and nutrients are highly dynamic. Yet, our knowledge of short-term phytoplankton dynamics associated with discharge disturbances and nutrient inputs remains elusive, especially in large rivers. Based on every three-day monitoring, we studied phytoplankton in the middle Loire River (France) and related to the daily variations in water discharge and the physical and chemical parameters. We focused on summer phytoplankton (2013 and 2014), where dissolved inorganic phosphorus concentration was potentially limiting growth. We identified eight discharge events, which increased suspended matter concentration and decreased chlorophyll-a concentration. The most significant environmental drivers of phytoplankton composition were discharge and water temperature, a sensitive proxy for meteorological forcing at short-time scale. The phytoplankton composition responded to changes in hydrology along with three distinct assemblage types, where even small water discharge increase induced a community response. Meroplanktic algae being able to withstand sedimentation and resuspension could take advantage of hydrological peaks, following the benthic retention hypothesis. Our results suggest that short-term dynamics are crucial to understanding community organisation and functioning in large river plankton, with meroplankton playing a decisive role in maintaining phytoplankton diversity and ecosystem functioning.
ano.nymous@ccsd.cnrs.fr.invalid (Alexandrine Pannard) 14 Dec 2023
https://hal.science/hal-04343848v1
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[insu-04606946] Improving calibration of groundwater flow models using headwater streamflow intermittence
Non‐perennial streams play a crucial role in ecological communities and the hydrological cycle. However, the key parameters and processes involved in stream intermittency remain poorly understood. While climatic conditions, geology and land use are well identified, the assessment and modelling of groundwater controls on streamflow intermittence remain a challenge. In this study, we explore new opportunities to calibrate process‐based 3D groundwater flow models designed to simulate hydrographic network dynamics in groundwater‐fed headwaters. Streamflow measurements and stream network maps are considered together to constrain the effective hydraulic properties of the aquifer in hydrogeological models. The simulations were then validated using visual observations of water presence/absence, provided by a national monitoring network in France (ONDE). We tested the methodology on two pilot unconfined shallow crystalline aquifer catchments, the Canut and Nançon catchments (Brittany, France). We found that both streamflow and stream network expansion/contraction dynamics are required to calibrate models that simultaneously estimate hydraulic conductivity and porosity with low uncertainties. The calibration allowed good prediction of stream intermittency, both in terms of flow and spatial extent. For the two catchments studied, Canut and Nançon, the hydraulic conductivity is close reaching 1.5 × 10 −5 m/s and 4.5 × 10 −5 m/s, respectively. However, they differ more in their storage capacity, with porosity estimated at 0.1% and 2.2%, respectively. Lower storage capacity leads to higher groundwater level fluctuations, shorter aquifer response times, an increase in the proportion of intermittent streams and a reduction in perennial flow. This new modelling framework for predicting headwater streamflow intermittence can be deployed to improve our understanding of groundwater controls in different geomorphological, geological and climatic contexts. It will benefit from advances in remote sensing and crowdsourcing approaches that generate new observational data products with high spatial and temporal resolution.
ano.nymous@ccsd.cnrs.fr.invalid (Ronan Abhervé) 10 Jun 2024
https://insu.hal.science/insu-04606946v1
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[hal-04522022] Measuring biodiversity vulnerability in French lakes – The IVCLA index
Assessing the vulnerability of ecosystems to biodiversity loss has become increasingly crucial in conservation and ecology research. This study proposed a methodology for measuring lake vulnerability to biodiversity loss employing an established framework that combines three components. For this, we measured the resilience (functional redundancy) and sensitivity (an index considering three characteristics of rarity) components for fish and phytoplankton communities. We also measured the exposure component of the main stressors in lakes. We then combined the three components and calculated the vulnerability index (IVCLA) using data from 255 French lakes. We found that all lakes exhibited low levels of resilience, elevated sensitivity regarding average values for fish and phytoplankton groups, and medium exposure to stressors associated with human activities. In addition, there were some discrepancies in resilience and sensitivity patterns between fish and phytoplankton groups, emphasizing the importance of considering information from multiple biological groups when assessing ecosystem vulnerability. Hydrological alterations and low water quality were key stressors related to higher lake vulnerability. Most French lakes have been classified as exhibiting moderate vulnerability. It is crucial to emphasize the potential increase in exposure risks, which could lead to even higher vulnerability levels and, subsequently, biodiversity loss in the future. The IVCLA index offers several advantages, including integrating multiple taxa groups and stressors. We recommend incorporating additional data, such as the resilience and sensitivity of the entire food web, and considering temporal responses to stressors to improve accuracy and predictive power. The IVCLA was developed with the purpose of serving as an effective tool for guiding environmental managers in designing conservation strategies and making informed decisions for lake ecosystems.
ano.nymous@ccsd.cnrs.fr.invalid (Barbbara Silva Rocha) 03 Jul 2024
https://hal.inrae.fr/hal-04522022v1
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[hal-04431653] The Four Interfaces' Components of Riparian Zones
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ano.nymous@ccsd.cnrs.fr.invalid (Gilles Pinay) 01 Feb 2024
https://hal.inrae.fr/hal-04431653v1
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[hal-04592312] Understanding temporal variability across trophic levels and spatial scales in freshwater ecosystems
Abstract A tenet of ecology is that temporal variability in ecological structure and processes tends to decrease with increasing spatial scales (from locales to regions) and levels of biological organization (from populations to communities). However, patterns in temporal variability across trophic levels and the mechanisms that produce them remain poorly understood. Here we analyzed the abundance time series of spatially structured communities (i.e., metacommunities) spanning basal resources to top predators from 355 freshwater sites across three continents. Specifically, we used a hierarchical partitioning method to disentangle the propagation of temporal variability in abundance across spatial scales and trophic levels. We then used structural equation modeling to determine if the strength and direction of relationships between temporal variability, synchrony, biodiversity, and environmental and spatial settings depended on trophic level and spatial scale. We found that temporal variability in abundance decreased from producers to tertiary consumers but did so mainly at the local scale. Species population synchrony within sites increased with trophic level, whereas synchrony among communities decreased. At the local scale, temporal variability in precipitation and species diversity were associated with population variability (linear partial coefficient, β = 0.23) and population synchrony (β = −0.39) similarly across trophic levels, respectively. At the regional scale, community synchrony was not related to climatic or spatial predictors, but the strength of relationships between metacommunity variability and community synchrony decreased systematically from top predators (β = 0.73) to secondary consumers (β = 0.54), to primary consumers (β = 0.30) to producers (β = 0). Our results suggest that mobile predators may often stabilize metacommunities by buffering variability that originates at the base of food webs. This finding illustrates that the trophic structure of metacommunities, which integrates variation in organismal body size and its correlates, should be considered when investigating ecological stability in natural systems. More broadly, our work advances the notion that temporal stability is an emergent property of ecosystems that may be threatened in complex ways by biodiversity loss and habitat fragmentation.
ano.nymous@ccsd.cnrs.fr.invalid (Tadeu Siqueira) 29 May 2024
https://hal.inrae.fr/hal-04592312v1
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[hal-04523305] L'infrarouge thermique aéroporté, un outil de connaissance des rivières face au changement climatique
[...]
ano.nymous@ccsd.cnrs.fr.invalid (Baptiste Marteau) 27 Mar 2024
https://hal.science/hal-04523305v1
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[hal-03528633] Landscape connectivity alters the evolution of density-dependent dispersal during pushed range expansions
As human influence reshapes communities worldwide, many species expand or shift their ranges as a result, with extensive consequences across levels of biological organization. Range expansions can be ranked on a continuum going from pulled dynamics, in which low-density edge populations provide the “fuel” for the advance, to pushed dynamics in which high-density rear populations “push” the expansion forward. While theory suggests that evolution during range expansions could lead pushed expansions to become pulled with time, empirical comparisons of phenotypic divergence in pushed vs. pulled contexts are lacking. In a previous experiment using Trichogramma brassicae wasps as a model, we showed that expansions were more pushed when connectivity was lower. Here we used descendants from these experimental landscapes to look at how the range expansion process and connectivity interact to shape phenotypic evolution. Interestingly, we found no clear and consistent phenotypic shifts, whether along expansion gradients or between reference and low connectivity replicates, when we focused on low-density trait expression. However, we found evidence of changes in density-dependence, in particular regarding dispersal: populations went from positive to negative density-dependent dispersal at the expansion edge, but only when connectivity was high. As positive density-dependent dispersal leads to pushed expansions, our results confirm predictions that evolution during range expansions may lead pushed expansions to become pulled, but add nuance by showing landscape conditions may slow down or cancel this process. This shows we need to jointly consider evolution and landscape context to accurately predict range expansion dynamics and their consequences.
ano.nymous@ccsd.cnrs.fr.invalid (Maxime Dahirel) 19 Aug 2024
https://hal.inrae.fr/hal-03528633v1
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[hal-04444942] Non-perennial segments in river networks
Non-perennial river segments - those that recurrently cease to flow or frequently dry - occur in all river networks and are globally more abundant than perennial (always flowing) segments. However, research and management have historically focused on perennial river segments. In this Review, we outline how non-perennial segments are integral parts of river networks. Repeated cycles of flowing, non-flowing and dry phases in non-perennial segments influence biodiversity and ecosystem dynamics at different spatial scales, from individual segments to entire river networks. Varying configurations of perennial and non-perennial segments govern physical, chemical and ecological responses to changes in the flow regimes of each river network, especially in response to human activities. The extent of non-perennial segments in river networks has increased owing to warming, changing hydrological patterns and human activities, and this increase is predicted to continue. Moreover, the dry phases of flow regimes are expected to be longer, drier and more frequent, albeit with high regional variability. These changes will likely impact biodiversity, potentially tipping some ecosystems to compromised stable states. Effective river-network management must recognize ecosystem services (such as flood risk management and groundwater recharge) provided by non-perennial segments and ensure their legislative and regulatory protection, which is often lacking. Non-perennial segments of rivers undergo cycles of flowing, non-flowing and dry phases, influencing ecosystem dynamics and services across the river network. This Review describes the occurrence, ecology and future of these intermittent and ephemeral flows and highlights the importance of protecting these segments. Non-perennial segments comprise over half of the global river network. Ongoing climate change and human activities will further increase the occurrence of river drying.Recurrent cycles of flowing, non-flowing and dry phases influence exchanges of water, energy, nutrients and organisms between non-perennial segments and connected perennial waters.Physical, chemical and biological processes in non-perennial segments affect water quality and quantity, and ecological integrity in downstream receiving waters and entire river networks.Historically, river science and management have focused on perennial river segments, neglecting the ubiquity and importance of non-perennial segments. This imbalance has often led to environmental problems such as poor water quality, loss of biodiversity and alteration of natural flow regimes at the river-network scale.Sustaining the water quality and ecological integrity of entire river networks and associated downstream waters requires integrated management strategies that explicitly consider non-perennial segments and their connections with perennial ones.
ano.nymous@ccsd.cnrs.fr.invalid (Thibault Datry) 07 Feb 2024
https://hal.inrae.fr/hal-04444942v1
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[hal-04328500] Distinct impacts of feeding frequency and warming on life history traits affect population fitness in vertebrate ectotherms
Abstract Body size shifts in ectotherms are mostly attributed to the Temperature Size Rule (TSR) stating that warming speeds up initial growth rate but leads to smaller size when food does not limit growth. Investigating the links between temperature, growth, and life history traits is key to understand the adaptive value of TSR, which might be context dependent. In particular, global warming can affect food quantity or quality which is another major driver of growth, fecundity, and survival. However, we have limited information on how temperature and food jointly influence life history traits in vertebrate predators and how changes in different life history traits combine to influence fitness and population demography. We investigate (1) whether TSR is maintained under different food conditions, (2) if food exacerbates or dampens the effects of temperature on growth and life history traits and (3) if food influences the adaptive value of TSR. We combine experiments on the medaka with Integral Projection Models to scale from life history traits to fitness consequences. Our results confirm that warming triggers a higher initial growth rate and a lower adult size, reduces generation time and increases mean fitness. A lower level of food exacerbates the effects of warming on growth trajectories. Although lower feeding frequency increased survival and decreased fecundity, it did not influence the effects of warming on fish development rates, fecundity, and survival. In contrast, feeding frequency influenced the adaptive value of TSR, as, under intermittent feeding, generation time decreased faster with warming and the increase in growth rate with warming was weaker compared to continuously fed fish. These results are of importance in the context of global warming as resources are expected to change with increasing temperatures but, surprisingly, our results suggest that feeding frequency have a lower impact on fitness at high temperature.
ano.nymous@ccsd.cnrs.fr.invalid (Simon Bazin) 07 Dec 2023
https://hal.inrae.fr/hal-04328500v1
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[insu-04556232] Simulation and calibration of headwater stream intermittency using a groundwater flow model
Recent research has highlighted the crucial role for ecological communities and the significant prevalence of temporary streams: over 50% of the world's rivers are temporary. However, the main parameters and processes involved in the stream intermittency remain poorly understood. The literature identifies several controlling factors, including meteorology, geology and land cover, but a major challenge remains: understanding the role of the subsurface, i.e. the effect of the aquifer's hydraulic properties. In line with the new definition of an intermittent river, “a non-perennial river or stream with a considerable connection to the groundwater table, having variable cycles of wetting and flow cessation, and with flow that is sustained longer than a single storm event”, we use a 3D process-based groundwater flow model at the catchment-scale to simulate stream flow and the spatio-temporal extension/contraction of the hydrographic network. Focusing on two crystalline catchments in Brittany (northwest France), with a similar temperate climate, we explore the combined effect of hydraulic conductivity K (transmission capacity) and porosity θ (storage capacity). We propose a calibration approach with performance criteria based solely on surface information: 1) stream flow measured at the catchment outlet and 2) mapping of the observed hydrographic network (for the low-water period: perennial streams and for the high-water period: perennial + intermittent streams). The calibration results show that the methodology leads to an optimal aquifer model for the 2 catchments (Canut: K = 4.5 x 10-5 m/s, θ = 0.1% and Nancon: K = 1.5 x 10-5 m/s, θ = 2.2%). For both catchments, the comparison of simulated versus observed stream flow, focusing on low flows, achieves an excellent NSElog>0.86. At the same time, the model reproduces very well the hydrographic network observed during both high and low water periods (Figure 1), resulting in a very good success criterion. Finally, the models are validated using data from discrete visual monitoring of stream hydrological conditions (national ONDE network). Based on these modelling results, we then discuss hydrogeological controls such as the role of aquifer storage capacity on headwater stream intermittency. We believe that the use of stream intermittency mapping, benefiting from innovations in crowdsourcing and remote sensing, will address the need for hydrological models and predictions for ungauged basins.
ano.nymous@ccsd.cnrs.fr.invalid (Ronan Abhervé) 23 Apr 2024
https://insu.hal.science/insu-04556232v1
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[hal-04298245] Caractérisation des habitats piscicoles d’une rivière intermittente par imagerie drone
La structuration morpho-écologique des cours d'eau est un des facteurs clefs de la répartition des habitats et implicitement de la qualité des milieux aquatiques fluviaux. Dans un contexte de réchauffement climatique global, ces milieux complexes et sensibles vont être de plus en plus concernés par des phénomènes d'assèchement partiel ou intégral de leur lit impactant les continuums écologiques piscicoles. Le besoin d'outils opérationnels est donc primordial pour étudier les variations physiques des tronçons de rivière et fournir des indicateurs caractérisant les méso-formes (seuils, mouilles, radiers, végétation rivulaire), leur répartition et leur suivi afin d'évaluer leur qualité. Le projet de recherche RIVERSIDE (Restitution du fractionnement des méso-habitats des rIVières intERmittenteS par Imagerie DronE) a pour objectifs, i) d'éprouver la capacité des données LiDAR et des images traitées par photogrammétrie à restituer les méso-formes des habitats, d'en extraire les caractéristiques physiques, iii) de croiser ces métriques avec les relevés piscicoles (inventaires localisés).
ano.nymous@ccsd.cnrs.fr.invalid (Jérôme Lejot) 21 Nov 2023
https://hal.science/hal-04298245v1
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[hal-04313500] A collaborative backbone resource for comparative studies of subterranean evolution: The World Asellidae database
Abstract Transition to novel environments, such as groundwater colonization by surface organisms, provides an excellent research ground to study phenotypic evolution. However, interspecific comparative studies on evolution to groundwater life are few because of the challenge in assembling large ecological and molecular resources for species‐rich taxa comprised of surface and subterranean species. Here, we make available to the scientific community an operational set of working tools and resources for the Asellidae, a family of freshwater isopods containing hundreds of surface and subterranean species. First, we release the World Asellidae database (WAD) and its web application, a sustainable and FAIR solution to producing and sharing data and biological material. WAD provides access to thousands of species occurrences, specimens, DNA extracts and DNA sequences with rich metadata ensuring full scientific traceability. Second, we perform a large‐scale dated phylogenetic reconstruction of Asellidae to support phylogenetic comparative analyses. Of 424 terminal branches, we identify 34 pairs of surface and subterranean species representing independent replicates of the transition from surface water to groundwater. Third, we exemplify the usefulness of WAD for documenting phenotypic shifts associated with colonization of subterranean habitats. We provide the first phylogenetically controlled evidence that body size of males decreases relative to that of females upon groundwater colonization, suggesting competition for rare receptive females selects for smaller, more agile males in groundwater. By making these tools and resources widely accessible, we open up new opportunities for exploring how phenotypic traits evolve in response to changes in selective pressures and trade‐offs during groundwater colonization.
ano.nymous@ccsd.cnrs.fr.invalid (Nathanaelle Saclier) 23 Apr 2024
https://hal.inrae.fr/hal-04313500v1
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[hal-04620643] Report on downscaling global climate projections for catchment-scale hydrological modelling
Intermittent rivers and ephemeral streams (IRES) account for more than half of the world's rivers. However, few studies have investigated the evolution of IRES under climate change. Aiming to overcome this problem, DRYvER proposed to provide daily hydrological projections, daily flow conditions and flow intermittence indicators in 6 European Drying River Networks (DRNs). The current work aims to produce reach-scale daily hydrological projections available for the period 1985-2100 for each DRN. To this end, coarse spatial resolution daily projections from Global Climate Models (GCMs) are downscaled to obtain high resolution projections over the period 1971-2100. Secondly, the high-resolution projections are used as input to the JAMS/J2000 model to obtain daily catchment-scale hydrological projections. Several GCMs are used as well as 3 shared socio-economic pathways (SSPs) to capture the uncertainty due to climate modelling and greenhouse gas emission scenarios. The results show that the methodology is able to reproduce the historical hydrological behaviour of the DRNs in terms of seasonality, with some difficulties in Morava and Vantaanjoki regarding summer discharge. Regarding the future periods, the responses of the six catchments were clearly different, showing an impact of climate change closely related to their location. Spring, summer and autumn discharges show a decrease for all catchments and all SSPs considered. For winter discharge, two of the catchments show a slight increase, but the other four also show a decrease of varying intensity.
ano.nymous@ccsd.cnrs.fr.invalid (Alexandre Devers) 21 Jun 2024
https://hal.inrae.fr/hal-04620643v1
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[hal-04620640] Report on future projections of flow intermittence for the 6 European focal DRN
Intermittent rivers and ephemeral streams (IRES) account for more than half of the world's rivers. However, few studies have investigated the evolution of IRES under climate change. To overcome this problem, DRYvER proposed to provide daily hydrological projections, daily flow conditions and flow intermittence indicators in 6 European Drying River Networks (DRNs). The current work aims to provide reach-scale daily flow conditions and flow intermittence indicators for the period 1985-2100 for each DRN. To this end, daily reach-scale hydrological projections - driven by several global climate models and Shared Socio-economic Pathways (SSP) - are used as input to a random forest algorithm trained in the historical period with actual observations of daily flow conditions. Once the flow conditions have been generated, a set of flow intermittence indicators is calculated to study the evolution of intermittence through the 21st century. Results highlight the coherence of the intermittence projections and intermittence reconstruction over the period 1985-2014. The inter-annual number of dry days of each reach of the DRNs from the projections are quite close to those from the reconstruction. Furthermore, the seasonality is well captured on all 6 DRNs, providing a reasonable confidence for future intermittence projections. The period 1985-2100 globally highlights a steady increase of the intermittence on all DRNs, with an intensity linked to the SSPs considered – i.e. higher increase with higher emissions - and the period considered. The study also suggests the transition of some reaches from perennial to intermittent, depending on the catchments, the SSP and the period considered.
ano.nymous@ccsd.cnrs.fr.invalid (Annika Künne) 21 Jun 2024
https://hal.inrae.fr/hal-04620640v1
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[hal-04313613] Spatiotemporal patterns of macroinvertebrate assemblages across mountain streams with contrasting thermal regimes
Water temperature is recognized as an important driver of aquatic ecosystems and is of increasing interest because of global warming. However, to date, no studies have disentangled the contribution of annual thermal variability from the contributions of annual thermal mean and other environmental variables to spatiotemporal patterns of macroinvertebrate assemblages in mountain streams. In this study, we explored patterns of macroinvertebrate biodiversity within and among 5 mountain stream sites in the Serio watershed (Orobic Alps, Northern Italy) along a gradient of annual water thermal variability (annual range: ~1–16°C) but with similar means. At each site, macroinvertebrates were sampled; physicochemical variables, flood disturbance, and resource availability were measured monthly over a year; and water temperature was monitored continuously. The relationship between macroinvertebrate assemblages and environmental conditions was described by separating time and space through co-inertia analyses. Results showed a strong temporal co-inertia, with floods and mean monthly temperature most associated with within-site macroinvertebrate temporal patterns (70% of total variance) and with the greatest effects on the abundance of stoneflies. Synchronous floods occurred in all sites and promoted changes in macroinvertebrate community composition through a loss of taxa and individuals, whereas monthly water temperature variations were associated with the replacement of individuals among taxa. Spatial differences (30% of the total variance) were mainly linked to geographical proximity, although annual thermal variability covaried with annual temporal dissimilarity in taxonomic composition, suggesting that temporal patterns also explain spatial differences. Overall, the study indicates that even when accounting for the overall environmental setting, the thermal regime remains an important driver of macroinvertebrate spatiotemporal patterns. Mountain streams are particularly subject to thermal variation, and an increase in mean water temperature and thermal variability will substantially influence community composition, with the strongest effects on cold stenothermal taxa. Large-scale research across mountain ranges is essential to properly assess how spatiotemporal thermal heterogeneity influences the distribution of macroinvertebrates, as well as to guide conservation strategies in the context of increasing global warming.
ano.nymous@ccsd.cnrs.fr.invalid (Luca Bonacina) 29 Nov 2023
https://hal.inrae.fr/hal-04313613v1
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[hal-04318861] How low can you go? Widespread challenges in measuring low stream discharge and a path forward
[...]
ano.nymous@ccsd.cnrs.fr.invalid (Erin Seybold) 02 Dec 2023
https://hal.science/hal-04318861v1
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[hal-04313486] Environmental DNA complements scientific trawling in surveys of marine fish biodiversity
Environment al DNA (eDNA) met abarcoding is a method to detect t axa from environment al samples. It is increasingly used f or marine biodiv ersity surv e y s. As it only requires water collection, eDNA metabarcoding is less in v asiv e than scientific trawling and might be more cost effective. Here, w e analy sed data from both sampling methods applied in the same scientific surv e y targeting Northeast Atlantic fish in the B a y of Biscay. We compared the methods regarding the distribution of taxonomic, phylogenetic, and functional diversity. We found that eDNA captured more taxonomic and phylogenetic richness than bottom trawling and more functional richness at the local scale. eDNA was less selective than trawling and detected species in local communities spanning larger phylogenetic and functional breadths, especially as it detected large pelagic species that escaped the tra wl, e v en though trawling detected more flat fish. eDNA indicated differences in fish community composition that were comparable to those based on tra wling. Ho w e v er, consistency betw een abundance estimates pro vided b y eDNA metabarcoding and trawl catches was low, even after accounting for allometric scaling in eDNA production. We conclude that eDNA metabarcoding is a promising method that can complement scientific trawling for multi-component biodiversity monitoring based on presence/absence, but not yet for abundance.
ano.nymous@ccsd.cnrs.fr.invalid (Pierre Veron) 29 Nov 2023
https://hal.inrae.fr/hal-04313486v1
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[hal-04318862] A metasystem approach to designing environmental flows
Abstract Accelerating the design and implementation of environmental flows (e-flows) is essential to curb the rapid, ongoing loss of freshwater biodiversity and the benefits it provides to people. However, the effectiveness of e-flow programs may be limited by a singular focus on ensuring adequate flow conditions at local sites, which overlooks the role of other ecological processes. Recent advances in metasystem ecology have shown that biodiversity patterns and ecosystem functions across river networks result from the interplay of local (environmental filtering and biotic interactions) and regional (dispersal) ecological processes. No guidelines currently exist to account for these processes in designing e-flows. We address this gap by providing a step-by-step operational framework that outlines how e-flows can be designed to conserve or restore metasystem dynamics. Our recommendations are relevant to diverse regulatory contexts and can improve e-flow outcomes even in basins with limited in situ data.
ano.nymous@ccsd.cnrs.fr.invalid (Mathis Messager) 02 Dec 2023
https://hal.science/hal-04318862v1
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[hal-04198078] Recent trends in the chemistry of major northern rivers signal widespread Arctic change
Rivers integrate processes occurring throughout their watersheds and aretherefore sentinels of change across broad spatial scales. River chemistryalso regulates ecosystem function across Earth’s land–ocean continuum,exerting control from the micro- (for example, local food web) to the macro-(for example, global carbon cycle) scale. In the rapidly warming Arctic, awide range of processes—from permafrost thaw to biological uptake andtransformation—might reasonably alter river water chemistry. Here weuse data from major rivers that collectively drain two-thirds of the ArcticOcean watershed to assess widespread change in biogeochemical functionwithin the pan-Arctic basin from 2003 to 2019. While the oceanward flux ofalkalinity and associated ions increased markedly over this time frame, nitrateand other inorganic nutrient fluxes declined. Fluxes of dissolved organiccarbon showed no overall trend. This divergence in response indicatesthe perturbation of multiple processes on land, with implications forbiogeochemical cycling in the coastal ocean. We anticipate that these findingswill facilitate refinement of conceptual and numerical models of currentand future functioning of Arctic coastal ecosystems and spur research onscale-dependent change across the river-integrated Arctic domain.
ano.nymous@ccsd.cnrs.fr.invalid (Suzanne Tank) 01 Feb 2024
https://hal.inrae.fr/hal-04198078v1
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[hal-04248122] The recovery of European freshwater biodiversity has come to a halt
Owing to a long history of anthropogenic pressures, freshwater ecosystems are among the most vulnerable to biodiversity loss. Mitigation measures, including wastewater treatment and hydromorphological restoration, have aimed to improve environmental quality and foster the recovery of freshwater biodiversity. Here, using 1,816 time series of freshwater invertebrate communities collected across 22 European countries between 1968 and 2020, we quantified temporal trends in taxonomic and functional diversity and their responses to environmental pressures and gradients. We observed overall increases in taxon richness (0.73% per year), functional richness (2.4% per year) and abundance (1.17% per year). However, these increases primarily occurred before the 2010s, and have since plateaued. Freshwater communities downstream of dams, urban areas and cropland were less likely to experience recovery. Communities at sites with faster rates of warming had fewer gains in taxon richness, functional richness and abundance. Although biodiversity gains in the 1990s and 2000s probably reflect the effectiveness of water-quality improvements and restoration projects, the decelerating trajectory in the 2010s suggests that the current measures offer diminishing returns. Given new and persistent pressures on freshwater ecosystems, including emerging pollutants, climate change and the spread of invasive species, we call for additional mitigation to revive the recovery of freshwater biodiversity.
ano.nymous@ccsd.cnrs.fr.invalid (Peter Haase) 23 Oct 2023
https://hal.umontpellier.fr/hal-04248122v1
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[hal-04177222] Do temperature and population size structure influence the quantity of fish eDNA in water?
Various factors can influence the concentration of eDNA found in the environment and blur the link between eDNA results and in situ fish abundances, biomasses or even occurrences. We studied the influence of one abiotic factor, the temperature, and one biotic factor, the fish size class, on the amount of fish eDNA detectable in water. To do so, we conducted two controlled experiments using tench (Tinca tinca, L) placed into outdoor mesocosms during 1 week. The quantification of fish eDNA abundances was performed using quantitative PCR after filtrating a large volume of water (30 L). The Bayesian hierarchical ANOVAs performed on qPCR results did not detect the effect of size class on eDNA amount, but fish eDNA concentration was shown to increase significantly when temperature rose by 6 °C (no effect detected at 3 °C). This suggests that fish assemblage quantification of two thermally contrasting sites through eDNA is not directly comparable.
ano.nymous@ccsd.cnrs.fr.invalid (Alix Hervé) 04 Aug 2023
https://hal.inrae.fr/hal-04177222v1
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[hal-04182605] Past and future discharge and stream temperature at high spatial resolution in a large European basin (Loire basin, France)
This paper presents retrospective simulations (1963-2019) and future projections (1976-2100) of daily time series of discharge and stream temperature for 52 278 reaches (median length of 1.3 km) over the Loire River basin (10 5 km 2) in France, using a physical process-based thermal model coupled with a semidistributed hydrological model. Retrospective simulations are based on the 8 km gridded Safran meteorological reanalysis over France. Twenty-first century projections are based on a subset of the 8 km gridded and bias-corrected DRIAS-2020 dataset over France. The discharge and stream temperature dataset stands out from existing ones thanks to its large scale and its high spatial resolution and the use of a physical processbased thermal model. The whole dataset is freely available and can be downloaded in NetCDF format from https://doi.org/10.57745/LBPGFS (Seyedhashemi et al., 2022a).
ano.nymous@ccsd.cnrs.fr.invalid (Hanieh Seyedhashemi) 17 Aug 2023
https://hal.inrae.fr/hal-04182605v1
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[hal-04479790] Citizen scientists can help advance the science and management of intermittent rivers and ephemeral streams
Abstract Intermittent rivers and ephemeral streams are the world's dominant type of river ecosystem and are becoming more common because of global change. However, the inclusion of intermittent rivers and ephemeral streams in water policies and management plans remains largely limited because monitoring schemes and tools are designed for perennial rivers. In the present article, we discuss how smartphone applications used by citizen scientists can quantify the extent and occurrence of intermittent rivers and ephemeral streams. We also introduce a new app, DRYRivERS, specifically designed to monitor intermittent rivers and ephemeral streams. After a year of use, we counted more than 3600 observations from more than 1900 river reaches across 19 countries and four continents. Through three case studies, we then show that citizen science can improve our knowledge of the prevalence of intermittent rivers and ephemeral streams in the landscape, enhance hydrological modeling and calibration, and guide managers in setting water abstraction restrictions. Together, our approach demonstrates how citizen science can be incorporated into environmental monitoring to better inform river management and policy.
ano.nymous@ccsd.cnrs.fr.invalid (Amélie Truchy) 27 Feb 2024
https://hal.inrae.fr/hal-04479790v1
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[hal-04178324] Comparing field, probabilistic, and 2D numerical approaches to assess gravel mobility in a gravel-bed river
Sediment transport is a key process that affects the morphology and ecological habitat diversity of rivers. As part of a gravel augmentation program to mitigate sediment deficit below a dam, gravel mobility in the Ain River in Eastern France was investigated by tracking of a large amount (n = 1063) of PIT-tagged gravels in the field, conducting a probabilistic approach based on published tracer studies, and performing two-dimensional (2D) numerical modeling of flow and bedload transport. This study highlights the strengths, weaknesses, and complementary aspects of the three approaches to the understanding of river gravel mobility. Thanks to recent technological improvements, PIT-tagged gravels provide an increasingly reliable and accurate representation of the bedload movement in the field, although it remains limited in spatio-temporal resolution. Based on an exponential distribution, the probabilistic approach correctly reproduces the average trend in travel distances by the different classes of particles over hydrological periods, including one or several significant floods. The 2D numerical modeling accounts for the variability of local hydrodynamic conditions and can simulate realistic displacement distributions for the different classes of particles with high spatio-temporal resolution. Numerical modeling is a very encouraging approach, which makes our study original because it is the first time that the estimation of mean travel distances, the application of an exponential distribution, and the comparison with a hydrodynamic model are combined. A more effective modeling strategy involves incorporating a probabilistic transport model in the 2D numerical model to reproduce the observed scatter of the individual particle trajectories.
ano.nymous@ccsd.cnrs.fr.invalid (Fanny Arnaud) 07 Aug 2023
https://hal.science/hal-04178324v1
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[hal-03368959] Coupling 3D hydraulic simulation and fish telemetry data to characterize the behavior of migrating smolts approaching a bypass
Human-induced river fragmentation is a major threat to migratory fish species. Restoringriver connectivity requires the construction of fish passage solutions, such as fishways forupstream and downstream migration. While many studies focussed on the upstream migra-tion of diadromous fishes, and especially of adult Atlantic salmons (Salmosalar), we analyzejuvenile behaviour under different hydraulic conditions at reservoir to improve the develop-ment of effective bypass systems for downstream passage of salmon smolt.Based on coupling three-dimensional (3D) computational fluid dynamics (CFD) simulationsto smolt positions tracked by two-dimensional (2D) telemetry, the present study aimed toexplore smolt behaviour in relation to hydraulic cues. More specifically, we explored howhydraulic conditions influence fish behaviour and how fish navigate depending on thisbehaviour. In 2017, 23 smolts were tracked in the reservoir of Poutes (Allier River, France),associated with different turbine discharge rates. 3D CFD simulations were performed andvalidated against field measurements in the reservoir upstream of the hydropower plant.The study of fish displacements in relation to flow conditions provided new insights withthe use of thrust force, swimming orientation and direction as means to precisely character-ize smolt behaviour, which can help in the design of downstream migration passage facili-ties. At Poutes dam, flow velocity, flow acceleration and turbulent kinetic energy are verylow and therefore can lead to fish disorientation. However, results underlined that having aminimum flow velocity of 20cm/s in reservoirs is sufficient to prevent delay and allowfish navigation;
ano.nymous@ccsd.cnrs.fr.invalid (Noor Ben Jebria) 08 Sep 2023
https://hal.inrae.fr/hal-03368959v1
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[hal-04151628] Past and future joint trends in river temperature and flow: implications for diadromous fish
Most key life-cycle events of organisms are synchronized by complex interactions of environmental cues to ensure optimal survival and growth of individuals and their offspring. However, this synchronicity is threatened by global change, which modifies the hydrological and thermal regimes of rivers worldwide. In particular, the asynchronous evolution of river temperature and flow can alter the duration and frequency of environmental windows suitable for the migration of diadromous fish. In this research project, we first developed the ‘Choc’ method to explore temporal CHanges in the OCcurrence of associations in bivariate time series. We applied this method to several case studies, which highlighted how global change has altered the conditions under which the endangered European eel and Atlantic salmon migrate, and how they have responded to these environmental changes. Recently, reconstructed (1963-2019) and projected (2020-2100) daily river temperature and flow data have been modelled over the entire hydrographic network of the Loire catchment (France). We combined this extensive dataset with daily fish passages available at fishways to assess the spatial and seasonal variability of trends in temperature-flow associations at a large scale. We then described how it has affected and will likely affect migration conditions of Atlantic salmon, allis shad and sea lamprey in the Loire catchment. Finally, we developed indicators to quantify past, present and future environmental suitability for their migration that allow comparison between rivers and tributaries, thereby providing operational results for the conservation of diadromous species and the prioritization of management actions in the context of global change.
ano.nymous@ccsd.cnrs.fr.invalid (Anthony Maire) 06 Jul 2023
https://hal.science/hal-04151628v1
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[hal-04176046] Riparian vegetation mitigates river warming: exploring its large scale effects on past and future thermal regimes
As air temperature increases worldwide due to climate change, stream temperature (Tw) is expected to follow a similar trajectory with even faster changes. In this study, we aimed at investigating and quantifying the extent to which riparian shading can help mitigate river warming at a large scale (105 km²). To do so, a physical process-based thermal model coupled with a semi-distributed hydrological model was used to reconstruct (1963-2019) and project (2005-2100) Tw for 52000 hydrographic sections of the Loire basin (France). This high spatial resolution (1 km) model includes a novel routine to account for riparian shading dynamically across seasons. Results showed that past and future increases in Tw were greater in relatively large rivers (Strahler order≥5), which was attributed partly to the mitigation effect of riparian shading observed on smaller streams. Indeed, riparian vegetation shading mitigated spring and summer Tw increases by up to 0.16°C per decade in headwater streams (i.e. < 30 km from the source) over the past six decades. Moreover, riparian shading could mitigate the future increase in summer Tw in small streams by 3.75°C to 5.17°C by the end of the 21st century, depending on the climate model and scenario from sparsely shaded reaches to highly shaded reaches. We complemented these results by exploring the consequences of theoretical scenarios of large-scale riparian restoration or loss on Tw changes. Our results suggest that the restoration and maintenance of riparian forests holds great promise to help mitigate the effects of global warming on rivers and their biodiversity.
ano.nymous@ccsd.cnrs.fr.invalid (Hanieh Seyedhashemi) 15 Aug 2023
https://hal.science/hal-04176046v1
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[hal-04148822] Spatio-temporal dynamics of habitat use by fish in a restored alluvial floodplain over two decades
Floodplain channels of rivers can serve as reproduction, nursery or refuge areas for fish. Although the complementary use of floodplain and main channels is known, few studies attempted to quantify this use and even fewer analysed its controlling factors. The objectives of this study are (1) to describe the spatio-temporal use of floodplain habitats and to identify their roles as complementary habitats for fish and (2) to analyse how abiotic variations and their modifications under restoration impact habitat use by fish. To meet these objectives, we analysed multi-site data collected over 20 years in eight restored sectors of the Rhône River. Results show that habitat use by fish is mainly related to spatial effects. As expected, rheophilic species were more abundant in lotic stations and limnophilic species in lentic ones. In addition, we identified an euryecious guild, grouping youngs of the year taxa, that used all types of habitats and particularly lentic floodplain channels with short life-span. Temporal effects combine (1) the effect of restoration, particularly in floodplain channels for which the connectivity regime was modified, (2) the effect of high flows upon the habitat use by fish that reinforces the nursery and refuge functions of floodplain channels. To conclude, our results demonstrate the importance of restoring habitat diversity and connectivity because habitats may have complementary functions for fish. Furthermore, our results also highlight that it is essential to account for temporal variations in order to better estimate the potential effects of restoration on river and their floodplains.
ano.nymous@ccsd.cnrs.fr.invalid (Anaëlle Bouloy) 03 Jul 2023
https://hal.science/hal-04148822v1
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[hal-04187405] SEINARIOS: Modelling river fish distribution under connectivity constraints
Anthropogenic change and its effects on rivers cause fish to adapt through a shift in their distribution. However, the management of rivers leads to connectivity constraints (dams, sluices, etc.) which impede this dynamic. Our study sought to characterize connectivity’s influence on fish distribution. To do so, we worked on the extended Seine River basin (France), a heterogeneous, 95,000 square kilometer area that includes more than 14,000 artificial barriers. Our analyses relied on a unique dataset of fish species abundance for 52 species, covering 20 years and 2,200 stations. We first calculated connectivity metrics, often overlooked in this context, from species-specific leptokurtic dispersal kernels, using the R package {riverconn} to account for asymmetrical dispersal (upstream and downstream). Second, we built a set of species distribution models (SDM) to explain current fish distribution in relation to climatic and hydrological conditions and land use. Third, to assess the importance of connectivity in fish species distribution, our innovative approach was to include connectivity metrics in the SDMs and estimate the contribution of these metrics to model performance. Our results will contribute to a better understanding and quantification of the importance of connectivity in river fish distribution in anthropized environments. Furthermore, this work will allow predicting biodiversity under scenarios of global change and open doors for application to different catchments.
ano.nymous@ccsd.cnrs.fr.invalid (Swann Felin) 24 Aug 2023
https://hal.inrae.fr/hal-04187405v1
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[hal-04148814] Past and future joint trends in river temperature and flow: implications for diadromous fish
Most key life-cycle events of organisms are synchronized by complex interactions of environmental cues to ensure optimal survival and growth of individuals and their offspring. However, this synchronicity is threatened by global change, which modifies the hydrological and thermal regimes of rivers worldwide. In particular, the asynchronous evolution of river temperature and flow can alter the duration and frequency of environmental windows suitable for the migration of diadromous fish. In this research project, we first developed the ‘Choc’ method to explore temporal CHanges in the OCcurrence of associations in bivariate time series. We applied this method to several case studies, which highlighted how global change has altered the conditions under which the endangered European eel and Atlantic salmon migrate, and how they have responded to these environmental changes. Recently, reconstructed (1963-2019) and projected (2020-2100) daily river temperature and flow data have been modelled over the entire hydrographic network of the Loire catchment (France). We combined this extensive dataset with daily fish passages available at fishways to assess the spatial and seasonal variability of trends in temperature-flow associations at a large scale. We then described how it has affected and will likely affect migration conditions of Atlantic salmon, allis shad and sea lamprey in the Loire catchment. Finally, we developed indicators to quantify past, present and future environmental suitability for their migration that allow comparison between rivers and tributaries, thereby providing operational results for the conservation of diadromous species and the prioritization of management actions in the context of global change.
ano.nymous@ccsd.cnrs.fr.invalid (Anthony Maire) 05 Jul 2023
https://hal.science/hal-04148814v1
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[hal-04213415] Glacier retreat reorganizes river habitats leaving refugia for Alpine invertebrate biodiversity poorly protected
Alpine river biodiversity around the world is under threat from glacier retreat driven by rapid warming, yet our ability to predict the future distributions of specialist cold-water species is currently limited. Here, we link future glacier projections, hydrological routing methods and species distribution models to quantify the changing influence of glaciers on population distributions of 15 alpine river invertebrate species across the entire European Alps, from 2020 to 2100. Glacial influence on rivers is projected to decrease steadily, with river networks expanding into higher elevations at a rate of 1% per decade. Species are projected to undergo upstream distribution shifts where glaciers persist but become functionally extinct where glaciers disappear completely. Several alpine catchments are predicted to offer climate refugia for cold-water specialists. However, present-day protected area networks provide relatively poor coverage of these future refugia, suggesting that alpine conservation strategies must change to accommodate the future effects of global warming.
ano.nymous@ccsd.cnrs.fr.invalid (M A Wilkes) 21 Sep 2023
https://hal.science/hal-04213415v1
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[hal-03738584] Distinct impacts of food restriction and warming on life history traits affect population fitness in vertebrate ectotherms
The reduction of body size with warming has been proposed as the third universal response to global warming, besides geographical and phenological shifts. Observed body size shifts in ectotherms are mostly attributed to the temperature size rule (TSR) stating that warming speeds up initial growth rate but leads to smaller size when food availability does not limit growth. Nevertheless, climate warming can decrease food availability by modifying biochemical cycles and primary production. Food availability can also influence growth, fecundity and survival and thus potentially modulate the effect of temperature on life history strategies and fitness. However, the interactive effects of temperature and food availability on life history traits have been mostly studied in small invertebrate species where life history traits have been mainly considered in isolation. In contrast, we have limited information on (1) how temperature and food availability jointly influence life history traits in vertebrate predators and (2) how changes in different life history traits combines to influence fitness and population growth. To fill this gap, we investigated under laboratory conditions the independent and interactive effects of temperature (20 or 30 °C) and food availability (restricted or ad libitum) on the growth, fecundity and survival of the medaka fish Oryzias latipes. We next used our empirical estimates of vital rates as input parameters of an Integral Projection model (IPM) to predict how modifications in vital rates translate into generation time and population growth rate (i.e. mean fitness). Our results confirm that warming leads to a higher initial growth rate and lower size leading to crossed growth curves between the two temperatures. Food-restricted fish were smaller than ad libitum fed fish throughout the experiment, leading to nested growth curves. Fish reared at 30 °C matured younger, had smaller size at maturity, had a higher fecundity but had a shorter life span than fish reared at 20 °C. Food restriction increased survival probabilities under both temperature conditions corresponding to a "eat little die old" strategy. According to the IPM, warming reduces generation time and increases mean fitness in comparison to the cold treatments. Food restriction increased generation time and fitness in the cold treatment but had no effect in the warm treatment. Our results highlight the importance of accounting for the interaction between temperature and food availability to understand how body size shifts can affects vital rates and population demography. This is of importance in the context of global warming as resources (e.g., phytoplankton and zooplankton communities in aquatic ecosystems) are predicted to change in size structure and total abundance with increasing temperatures. Interestingly, our results suggest that food restriction has a weaker effect on fish mean fitness under warming.
ano.nymous@ccsd.cnrs.fr.invalid (Simon Bazin) 09 May 2023
https://hal.inrae.fr/hal-03738584v4
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[hal-04305582] N‐dimensional hypervolumes in trait‐based ecology: Does occupancy rate matter?
Abstract Many methods for estimating the functional diversity of biological communities rely on measuring geometrical properties of n‐dimensional hypervolumes in a trait space. To date, these properties are calculated from individual hypervolumes or their pairwise combinations. Our capacity to detect functional diversity patterns due to the overlap of multiple hypervolumes is, thus, limited. Here, we propose a new approach for estimating functional diversity from a set of hypervolumes. We rely on the concept of occupancy rate, defined as the mean or absolute number of hypervolumes enclosing a given point in the trait space. Furthermore, we describe a permutation test to identify regions of the trait space in which the occupancy rate of two sets of hypervolumes differs. We illustrate the utility of our approach over existing methods with two examples on aquatic macroinvertebrates. The first example shows how occupancy rate relates to the stability of trait space utilisation due to increased flow intermittency and allows the identification of taxa in regions of the trait space with low occupancy rates. The second example shows how the permutation test based on occupancy rates can detect differences in trait space utilisation due to river morphology variation even with a high degree of overlap among input hypervolumes. Our newly developed approach is particularly suitable in functional diversity analysis when investigating patterns of overlap among multiple hypervolumes. We emphasise the need to consider analyses based on occupancy rate into functional diversity estimation. Read the free Plain Language Summary for this article on the Journal blog.
ano.nymous@ccsd.cnrs.fr.invalid (Alex Laini) 24 Nov 2023
https://hal.inrae.fr/hal-04305582v1
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[hal-04646632] Modélisation de la distribution des abondances des communautés aquatiques du bassin versant de la Loire
Afin de préserver la biodiversité d’eau douce, il est impératif de comprendre comment l’environnement structure les communautés aquatiques et la distribution spatiale des occurrences des espèces. La modélisation de la distribution des espèces constitue un outil de choix, et est très utilisé dans le contexte actuel du changement climatique. Tandis que les modèles de distribution d’espèces sont essentiellement basés sur des données de présence/absence, les données d’abondance sont bien plus informatives sur l’état de santé des populations (e.g. risques d’extinction) et leur potentiel d’adaptation face aux perturbations de leur environnement. Le nombre croissant d’étude sur la distribution de l’abondance des espèces montre l’intérêt mais aussi le challenge que représente le développement de telles méthodes. Bien que la disponibilité d’importants jeux de données sur les abondances de nombreuses espèces à large échelle soient en nette augmentation, la modélisation de l’abondance n’est explorée que pour quelques taxons et à une échelle géographique relativement restreinte. Nous avons développé des modèles de distribution des abondances pour une cinquantaine de poissons et de macroinvertébrés sur le bassin versant de la Loire (105 km²). Nous avons utilisé les données issues des stations de suivis hydrobiologiques nationales (&gt;1000 stations) et des données environnementales à haute résolution spatiale (température de l’eau, variables hydrauliques) disponibles à l’échelle du bassin grâce à des modèles basés sur les processus physiques. Afin de dépasser les verrous rencontrés dans le développement de modèles d’abondance (e.g. sur-représentation des absences, large gamme de valeurs), nous proposons une approche de modélisation des classes d’abondance par ordinal forest (méthode de machine learning). Les perspectives et les limites de l’utilisation de ces modèles seront présentés. La possibilité de projeter les abondances potentielles futures sous divers scénarios de changement climatique sera explorée en vue d’adresser le potentiel devenir des communautés aquatiques comme l’homogénéisation des espèces, les déplacements des communautés.
ano.nymous@ccsd.cnrs.fr.invalid (Coline Picard) 12 Jul 2024
https://hal.science/hal-04646632v1
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[hal-04381990] Evolution of discharge and stream temperature from past to future in a large European River basin
Both discharge (Q) and stream temperature (Tw) are the key factors affecting water quality and the suitability of instream habitats, which are expected to experience substantial evolutions due to climate change. However, the absence of continuous and long-term data of Tw at a large scale limits our understanding of the spatio-temporal variations of Tw and their control factors, like riparian vegetation, strahler order, hydroclimate. The present study used a physically-based thermal model (T-NET), coupled with a semi-distributed hydrological model (EROS) using SAFRAN meteorological reanalysis data provided of M&#233;t&#233;o-France to reconstruct past daily Q and Tw over the 1963-2019 period for 52&#160;000 hydrographic reaches of the Loire basin (100&#160;000 km&#178;), France. Three regionalized climate projections under several future emissions scenarios (available on the DRIAS portal: www.drias-climat.fr) were used to project future daily time series of these variables over the 2005-2100 period. The results over the 1963-2019 period showed that the increase of the Tw was higher than those air temperature (Ta) in spring, summer and autumn for the majority of the reaches of the basin. Indeed, Tw increased for almost all reaches and all seasons (average = +0.38&#176;C/decade) with the largest increase in the spring (Mar-May) (range=+0.11 to +0.76&#176;C per decade) and in summer (Jun-Aug) (+0.08 to +1.02&#176;C per decade). Highest spring and summer increases were generally found in the south of the basin (Massif Central and Limousin plateau) and in higher Strahler order where a larger increase in Ta (up to 0.67 &#176;C/decade) and a larger decrease in Q (up to -16%/decade) occurred jointly. &#160; Depending on climate models, scenarios and seasons,future projections showed changes in seasonal flow and water temperature. Seasonal median flow over the basin would be between -40% and +35% for the middle of the 21st century (2040-2079) compared to the 1990-2019 period. For the end of the century (2070-2099), flow change would be between -53% and +73%. A clear increase in future Tw was also found with seasonal &#160;median increases of +0.7 to +2.7&#176;C in the middle (2040-2079) and of +0.8&#176;C to +5.0&#176;C, &#160;at the end of the century (2070-2099). These climate-induced changes in Q and Tw could help us to explain shifts in the phenology and geographical distribution of cold-water species. Moreover, they highlight that we should take vital actions for both adaptation and mitigation strategies. In this regard, we found that some of these climate change-induced impacts on Tw can be mitigated through the restoration and maintenance of riparian shading specially in small streams.
ano.nymous@ccsd.cnrs.fr.invalid (Florentina Moatar) 09 Jan 2024
https://hal.science/hal-04381990v1
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[hal-04148794] Joint temporal trends in river discharge and temperature over the past 57 years in a large European basin: implications for diadromous fish
Stream temperature and discharge are two fundamental triggers of key periods of the life cycle of aquatic organisms such as the migration of diadromous fish. However, the increase in stream temperature, more frequent and severe droughts, and asynchronous evolution of stream temperature and discharge due to climate change can modify the duration and frequency of favorable temperature-flow associations for the realization of species’ ecological processes. In this study, we investigated the influence of changes in favorable temperature-flow velocity associations for the upstream migration of Atlantic salmon, Alis shad and Sea lamprey at the scale of the Loire River basin (100000 km²). First, we used a physically-based thermal model (T-NET), coupled with a semi-distributed hydrological model (EROS) to reconstruct continuous daily times series over the 1963-2019 period (Seyedhashemi et al., 2022). Current velocity (V) was estimated using discharge through a hydraulic geometry model (Morel et al., 2020). We identified suitable water temperature-flow velocity associations for the migration of the three studied species based on (1) the literature and (2) observed migration recorded at fish passage stations. Using the “Choc method” (Arevalo et al., 2020), we then quantified the changes in frequency of occurrence of these suitable environmental windows over the past six decades across the hydrographic network of the Loire River basin. Our results showed that the greatest increases in stream temperature were associated with the greatest decreases in flow velocity over the past six decades. We also found that the frequency of suitable temperature-velocity associations for upstream migration of Atlantic salmon has significantly reduced, mainly in the southern part of the basin. In contrary, the frequency of suitable associations for upstream migration of the two other species has mainly increased. These results highlighted strong disparities in the consequence of global changes on fish migratory processes among species and in space. This work provides operational results for the management of these threatened diadromous species and the prioritization of management measures in a context of climate change.
ano.nymous@ccsd.cnrs.fr.invalid (Hanieh Seyedhashemi) 03 Jul 2023
https://hal.science/hal-04148794v1
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[hal-04602264] Intermittent rivers and ephemeral streams are pivotal corridors for aquatic and terrestrial animals
Abstract Rivers are efficient corridors for aquatic animals, primarily under the assumption of perennial flow. However, the recognition that river drying is a common and widespread phenomenon requires reexamining animal movement through river networks. Intermittent rivers and ephemeral streams have been overlooked when studying animal movement, even though approximately 60% of the global river network dries. In the present article, we extend the current focus of river ecology by integrating the effects of drying on the movement of aquatic and terrestrial animals. Moreover, we introduce a conceptual model that challenges the current bias, which is focused on perennial waterways, by encompassing animal movement across hydrologic phases (nonflowing, flowing, dry, rewetting) and habitats (aquatic, terrestrial). We discuss their corridor function in conservation and restoration planning and identify emerging research questions. We contend that a more comprehensive and inclusive view of animal movement in dry channels will advance ecological understanding of river networks and respective conservation efforts.
ano.nymous@ccsd.cnrs.fr.invalid (María Mar Sánchez-Montoya) 05 Jun 2024
https://hal.inrae.fr/hal-04602264v1
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[hal-04177227] Assessing resilience and sensitivity patterns for fish and phytoplankton in French lakes
Ecosystem vulnerability is crucial information for conservation managers. We assessed the sensitivity and resilience (vulnerability components) patterns of fish and phytoplankton assemblages in French lakes (natural and artificial). We measured resilience (functional redundancy) and sensitivity, an index considering three characteristics of rarity for species. We hypothesized that geographically close lakes have similar resilience and sensitivity for fish assemblages (H1). Then, we tested the correlation between environmental gradients and resilience and sensitivity components, assuming that fish and phytoplankton do not respond similarly to environmental factors and that, consequently, there is no congruence between sensitivity and resilience patterns between of two groups. Also, we tested the hypotheses that species-rich assemblages show higher resilience and sensitivity in French lakes (H2); the highest values of resilience and sensitivity are related to phytoplankton (H3); and assemblages from natural lakes have higher resilience and sensitivity level (H4). We found similar resilience levels in spatially close fish assemblages due to fish dispersal limitations that contributed to create regional patterns in functional structure. Besides, acidity and eutrophication processes are good indicators of sensitivity level for fish. There is a mismatch in resilience and sensitivity levels between fish and phytoplankton, reinforcing importance of using a multi-taxa approach. Also, the components were positively related to taxonomic richness in assemblages showing importance of conserving biodiversity. Finally, we observed higher values of resilience and sensitivity for phytoplankton, as expected for a highly diverse group. Additionally, phytoplankton assemblages in natural lakes showed higher resilience levels than artificial environments, confirming the importance of preserving natural systems to conserve ecosystem functionality.
ano.nymous@ccsd.cnrs.fr.invalid (Barbbara Silva Rocha) 04 Aug 2023
https://hal.inrae.fr/hal-04177227v1
