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Suivi des processus de revégétalisation en lit endigué sur des bancs déboisés et arasés : le cas de l’Isère en Combe de Savoie
No full textInternational audienceTo understand and characterize the effects of works aimed at limiting vegetation encroachment, it is necessary to rely on accurate data on the trajectories of riparian environments both in the diagnosis phase and after vegetation removal. Remote sensing tools are key in meeting those challenges as they enable standardised monitoring and are increasingly available to river managers. Using a case study on the Isère River in Combe de Savoie where the revegetation of gravel bars is leading to a loss of biodiversity and an increase in flood risks, we demonstrate the value of high spatial and temporal resolution monitoring using drones to characterise the spatio-temporal dynamics of vegetation following clearing, stump removal and the reshaping of gravel bars. To do this, we use bi-annual campaigns during the growing season to retrace the dynamics of fine sediments and vegetation patches that have colonized the gravel bars. By assessing the age, growth and responses of vegetation units to winter floods over time, these data make it possible to characterize the dynamics of vegetation recruitment and establishment and thus to gain a more general understanding of the evolution of fluvial forms following interventions. Coupling these dynamics with the hydrology during the summer season will enable a better assessment of its effects on the recruitment and establishment of vegetation.Afin de comprendre et caractériser les effets des travaux destinés à limiter les processus de végétalisation en rivière, il est nécessaire de s’appuyer sur des données d’évaluation fiables des trajectoires des milieux riverains, cela tant dans les phases de diagnostic que dans les phases post-travaux. Les outils de la télédétection fluviale sont importants pour répondre à ces enjeux car ils permettent de réaliser un suivi standardisé et sont de plus en plus accessibles aux gestionnaires des cours d’eau. En prenant pour exemple le cas de l’Isère en Combe de Savoie où la végétalisation des bancs entraine une perte de biodiversité et une augmentation des risques d’inondation, nous montrons l’intérêt d’un suivi à haute résolution spatiale et temporelle par drone pour caractériser les dynamiques spatio-temporelles de la végétation après les travaux de déboisement, de dessouchage et de remodelage des bancs. Pour ce faire, nous nous appuyons sur des campagnes biannuelles encadrant la saison végétative et permettant de retracer la dynamique des tâches de sédiments fins et de végétation qui se sont développées sur les bancs. En évaluant l’âge, la croissance et la réponse des unités végétales aux crues hivernales au cours du temps, ces données permettent de caractériser les dynamiques de recrutement et d’établissement des végétations et ainsi de comprendre plus globalement l’évolution des formes fluviales suite aux interventions. Croiser ces dynamiques avec l’hydrologie au cours de la saison estivale permettra par la suite de mieux évaluer ses effets sur le recrutement et l’établissement de la végétation
Phenotypic diversity of brown trout (Salmo trutta L.) during the late Upper Pleistocene and Early Holocene in the glacial refugium of Iberia
No full textInternational audienceHuman populations have relied on fish for food for thousands of years, as evidenced in numerous Palaeolithic archaeological sites across Europe. In this paper, we investigate past populations of brown trout (Salmo trutta L.) along the Bay of Biscay coast before, during, and after the Last Glacial Maximum and compare their phenotypic diversity with modern populations. A total of 270 salmonid vertebrae from 11 archaeological sites in Spain and France were analysed, which span c. 30 to 9 kyr cal B.P. Species identification, combining ZooMS analyses with vertebral body size, confirmed 219 specimens as brown trout, and we present a model for salmonid species identification based on vertebral size. Stable isotope analyses of carbon and nitrogen reveal a continuum of habitat use patterns. After testing multiple published regression models for body length estimation in brown trout, we develop a novel linear regression model alongside a protocol for age estimation. Overall, the analysis of body size, age and migratory ecotype demonstrates that the phenotypic diversity of brown trout populations during the Pleistocene-Holocene transition is comparable to that of modern populations, reinforcing the role of the Iberian glacial refugium in maintaining diversity during the Last Glacial Maximum. The finding of large freshwater trout alongside sea trout in human-occupied archaeological sites further suggests the exploitation of both riverine and marine fish resources by human populations.</div
Eléments de réponse relatifs à la note « La continuité écologique, qu'en pensent les truites de la Loire ? » par P. Cadet et C. Lévêque
No full textLa note rédigée par P. Cadet et C. Lévêque vise à remettre en question la politique de restauration de la continuité écologique arguant que :i)les biomasses de truite commune (Salmo trutta) de certaines têtes de bassin versant de la Loire sont impactées par l’agent rosette (Sphaerothecum destruens) un oomycète parasite véhiculé par le pseudorsabora ou goujon asiatique (Pseudorasbora parva), ii)la restauration de la continuité écologique aggrave la situation en favorisant la colonisation des zones à truite par le goujon asiatique, iii)la truite commune est une espèce « sédentaire » et qui de fait n’est pas impactée par les obstacles à l’écoulement (seuils de moulin notamment)iv)les obstacles à l’écoulement atténuent le réchauffement de l’eau et ainsi favorisent les populations de truites.Nous n’exposerons ici que des arguments scientifiques en réponse à ces affirmations sans nous intéresser aux assertions des auteurs quant à l’administration et aux politiques publiques
Neglected impacts of plant protection products on invertebrate aquatic biodiversity: a focus on eco-evolutionary processes
No full textInternational audienceThe application of plant protection products (PPPs) may have delayed and long-term non-intentional impacts on aquatic invertebrates inhabiting agricultural landscapes. Such effects may induce population responses based on developmental and transgenerational plasticity, selection of genetic resistance, as well as increased extirpation risks associated with random genetic drift. While the current knowledge on such effects of PPPs is still scarce in non-target aquatic invertebrate species, evidences are accumulating that support the need for consideration of evolutionary components of the population response to PPPs in standard procedures of risk assessment. This mini-review, as part of a contribution to the collective scientific assessment on PPP impacts on biodiversity and ecosystem services performed in the period 2020-2022, presents a brief survey of the current results published on the subject, mainly in freshwater crustaceans, and proposes some research avenues and strategies that we feel relevant to fill this gap
The use of copper as plant protection product contributes to environmental contamination and resulting impacts on terrestrial and aquatic biodiversity and ecosystem functions
No full textErratum : 10.1007/s11356-025-36012-3International audienceCopper-based plant protection products (PPPs) are widely used in both conventional and organic farming, and to a lesser extent for non-agricultural maintenance of gardens, greenspaces, and infrastructures. The use of copper PPPs adds to environmental contamination by this trace element. This paper aims to review the contribution of these PPPs to the contamination of soils and waters by copper in the context of France (which can be extrapolated to most of the European countries), and the resulting impacts on terrestrial and aquatic biodiversity, as well as on ecosystem functions. It was produced in the framework of a collective scientific assessment on the impacts of PPPs on biodiversity and ecosystem services in France. Current science shows that copper, which persists in soils, can partially transfer to adjacent aquatic environments (surface water and sediment) and ultimately to the marine environment. This widespread contamination impacts biodiversity and ecosystem functions, chiefly through its effects on phototrophic and heterotrophic microbial communities, and terrestrial and aquatic invertebrates. Its effects on other biological groups and biotic interactions remain relatively under-documented
Recommendations to reduce the streetlight effect and gray areas limiting the knowledge of the effects of plant protection products on biodiversity
No full textInternational audiencePreserving biodiversity against the adverse effects of plant protection products (PPPs) is a major environmental and societal issue. However, despite intensive investigation into the ecotoxicological effects of PPPs, the knowledge produced remains fragmented given the sheer diversity of PPPs. This is due, at least in part, to a strong streetlight effect in the field of ecotoxicology. Indeed, while some PPPs have been investigated in numerous ecotoxicological studies, there are many for which the scientific literature still has little or no information on their ecotoxicological risks and effects. The PPPs under the streetlight include a large variety of legacy substances and a more limited number of more recent or currently-in-use substances, such as the herbicide glyphosate and the neonicotinoid insecticides. Furthermore, many of the most recent PPPs (including those used in biocontrol) and PPP transformation products (TPs) resulting from abiotic and/or biotic degradation are rarely addressed in the international literature in the field of ecotoxicology. Here, based on a recent collective scientific assessment of the effects of PPPs on biodiversity and ecosystem services in the French and European contexts, this article sets out to illustrate the limitations and biases caused by the streetlight effect and numbers of gray areas, and issue recommendations on how to overcome them
Environmental Matrices Need Consideration: Insights From Water and Biofilm Environmental DNA for Multi‐Taxonomic Biomonitoring
No full textInternational audienceEnvironmental DNA (eDNA) is revolutionizing biodiversity monitoring, offering a unique approach to assess multi‐taxonomic diversity with various applications related to evaluation, protection, and restoration of aquatic ecosystems. However, there is still a lack of sufficient studies to assess the complementarity of various environmental matrices and their contribution to enhancing biodiversity detection. This study evaluates the impact of eDNA sampling in different matrices to measure biodiversity of different taxonomic groups. We set up a year‐long eDNA sampling of water and biofilm matrices in a large lake littoral zone (Lake Geneva), focusing on microalgae, benthic macroinvertebrates, and fish. We first assessed primer specificity, which was high for microalgae (23S) and fish (12S) but was lower for macroinvertebrates (COI). We then evaluated the complementarity of eDNA signals in water and biofilms. For microalgae, communities from biofilm and water were highly different: water eDNA almost exclusively detected planktonic taxa while biofilm eDNA detected predominantly benthic taxa. For macroinvertebrates, communities in water and biofilms were also different, and biofilm eDNA could detect mostly Chironomidae. Finally, for fish, eDNA of both matrices enabled us to detect similar communities even if a few rare species were detected only in water. In the framework of the assessment of ecosystem quality or restoration actions success, we recommend diversifying matrices to collect eDNA to capture a complete picture of microalgae and macroinvertebrate communities. For fish, it is possible to sample water or biofilms, keeping in mind that water has become a standard practice for fish eDNA sampling
Modelling the distribution of rare and data-poor diadromous fish at sea for protected area management
No full textABSTRACT Anthropogenic pressures have resulted in declines in diadromous fish. Many diadromous fish which were commercially important are now threatened and protected. Little is known about their marine life history phases, and no observation-based Species Distribution Model exists for this group of species at sea. Yet, fisheries dependent and independent data could provide new insights into the distribution of diadromous fish at sea. We collated a database of 168 904 hauls from fisheries observer bycatch data and scientific fisheries surveys, from eastern Atlantic and Mediterranean waters. The distribution of eleven rare and data-poor diadromous fish (shads, lampreys, salmonids, the European eel, the thinlip mullet, smelt and the European flounder) were modelled. A Bayesian site occupancy model, that incorporates imperfect detection to account for repeat detections and non-detections, the non-random nature of fishing gear type and spatial autocorrelation was used. From the model outputs, we explored bycatch risk and the role of MPAs, required under the Marine Strategy Framework Directive and Habitat Directive and assessed. Diadromous fish were observed within relatively shallow coastal areas. Species specific gear bycatch trends were observed. Core distribution areas corresponded to their known water basin presence, indicating connectivity with their freshwater habitats. Numerous Habitat Directive Marine Protected Areas were found to be of relevance. Given the coastal distribution of these species, they are exposed to higher anthropogenic pressures from both terrestrial and marine environments. Risk of bycatch at sea for most species appears to be low. Nonetheless, for threatened individuals, even a small amount of bycatch may impact their populations, especially since misreporting is likely to be high. Differences in catchability between gears highlight potential benefits of limiting access of certain gears within protected areas to reduce bycatch
Energy restriction cancels the effect of temperature on the growth of common soles (Solea solea) in the Gironde estuary
No full textInternational audienceEstuarine and coastal ecosystems are key nursery habitats for the development and growth of many juveniles of marine fish species. Human-induced environmental changes, to which coastal and estuarine areas are particularly sensitive, will largely impact juveniles’ life history traits and consequently, the whole population at sea. Increase of water temperature is the best described and predicted environmental change related to climate change, and will certainly affect the nursery function of estuarine areas. Yet, our capacity to estimate consequences are limited and lack mechanistic models applied at the population level. As a major estuary of Western Europe, the Gironde estuary is a relevant case study to evaluate the effects of rising temperature on fish populations.To study the specific impact of temperature on life history traits of juvenile common soles (Solea solea) in the Gironde estuary, we used a bioenergetic model based on DEB theory. Since the estuary is supposed to have reached its maximum carrying capacity, effects were also estimated in a context of limited energy availability, with forecast scenario based on IPCC previsions.As soles in the Gironde estuary are below their thermal optimum, growth and development are expected to accelerate with increased temperature when food is not a limiting factor. Consequently, soles reach maturity sooner and grow larger. However, when we consider a restriction in available energy, linked to limited carrying capacity of the estuary, the effect of temperature is cancelled and changes in life history traits are negligible. However, a reduced energy in the reserve is estimated, which might alter the response to other environmental changes