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Modèles Castor : Evaluer l'impact d'un organisme ingénieur des cours d'eau : le castor d'Europe
No full textEn se basant sur des données acquises par le Réseau Castor de l’OFB, notre travail a abordé deux objectifs : (1) mieux comprendre la dynamique de colonisation de l’espèce et tenter d’identifier les facteurs en jeu et (2) analyser la diversité de la configuration des barrages et tester dans quelle mesure elle est conditionnée par les caractéristiques des cours d’eau sur lesquels ils sont implantés.Nous avons pu confirmer l’influence du temps et de la proximité des colonies sur la dynamique de colonisation de l’espèce dans les bassins versants français les plus colonisés. Les faibles liens observés entre cette dynamique de colonisation et l’environnement aquatique et terrestre sur les territoires des castors et le contexte environnemental ne permettent pas d’inférer sur les facteurs environnementaux favorisant la recolonisation. En effet, à ce stade, nous ne pouvons pas distinguer si ces liens sont réels ou sont générés par les bruits observés dans les données. De futures investigations de ces données du Réseau Castor utilisant des méthodes d’analyses spatialisées ou intégrant des covariables spatialisées pourraient permettre de confirmer ces liens.Nous avons par ailleurs montré qu’il existait une grande diversité de configuration dans les barrages rencontrés sur le territoire français portant en particulier sur leur taille, les matériaux qui les constituent et leur capacité à retenir l’eau et créer une retenue. Deux éléments structurant majeurs du point de vue des caractéristiques des barrages ressortent : la capacité à générer des débordements au-delà du lit mineur et l’existence de succession d’ouvrages dans un périmètre proche. Nous avons pu montrer qu’il existait un lien significatif, bien que relativement faible entre la configuration des barrages et les caractéristiques des cours d’eau et des milieux terrestres proches. La prise en compte de données plus précises sur la morphologie et la topographie des cours d’eau et de la vallée, le régime des débits, la végétation rivulaire et les pressions humaines qui s’y exercent devrait permettre de préciser et d’affiner ces relations
Very-High Resolution Coral Reef Habitat Mapping using Pleiades Satellite Imagery in Mayotte, Indian Ocean
No full textInternational audienceTropical coral reefs are the most biodiverse ecosystems on the planet. Unfortunately, increasing direct (e.g., overfishing, change in land use) and indirect (e.g., ocean acidification, sea-level rise, global warming, storms) human pressures are causing rapid declines in marine biodiversity globally, calling for more careful monitoring of sensitive ecosystems. If environmental baseline data like marine habitat maps are increasingly required to manage coastal environments, they are often lacking or are only available at a resolution that do not meet the needs of management. Such deficiencies hamper the implementation of effective management strategies and monitoring efforts.Here, we developed a method for conducting very high-resolution (sub-meter) mapping of benthic habitats semi-automatically across the 195km of Mayotte’s reef flat, a French island of the southwestern Indian Ocean. The mapping was performed using 50-cm resolution Pleiades satellite imagery from 2021-2023 and LiDAR-derived bathymetry. Satellite images were supplemented by underwater images acquired along 185 transects using a GoPro camera fixed to a diver propulsion vehicle. To achieve a very high spatial accuracy, underwater images were positioned with a few centimeters accuracy using a Global Navigation Satellite System (GNSS) system and post-processed kinematic (PPK) corrections. Geo-referenced image frames were extracted from the videos and integrated for annotations into CoralNet, a free online benthic image analysis software using semi-automatic deep learning analysis. About 10% of the video frames (3045 images) were annotated, allowing the analysis of over 27,000 image and calculate habitats’ covers on the reef. Satellite images were segmented using an Object-Based Image Analysis (OBIA) approach (i.e., the "Large-Scale Mean-Shift" (LSMS) segmentation method) and segments properties were used with other variables in a Random Forest pixel-based classification. To ensure replicability, data processing and analyses were conducted using free and open source software Orfeo ToolBox, QGIS, and R Stats.Thirteen benthic habitats, extending from coastal mangroves to the outer reef slope, were mapped at the pixel level. The LSMS segmentation method applied to Pléiades images created54,706 segments. CoralNet classifiers achieved 65% accuracy, while the Random Forest models reached an accuracy of 76%. The composition of benthic assemblages varied significantly aroundthe island, with changes in live corals accompanied by a rise in muddy habitats, turf, and dead corals as anthropogenic pressures intensify.The detailed habitat maps produced through this project will serve as an essential management tool to inform the management of Mayotte’s coastal waters. In December 2024, Mayotte experienced the very destructive Chido cyclone that strongly impacted the island, its population, and its terrestrial and marine ecosystems. By using satellite images acquired just before the cyclonic event, maps can serve as reference data, and help assess the cyclone's impact on the island's marine ecosystems
Pollinator‐Promoting Interventions in European Urban Habitats—A Synthesis
No full textInternational audiencePollinators receive considerable interest due to their fundamental role in ecosystem functioning and human well‐being. Unlike farmlands, studies of urban pollinator‐promoting interventions are scarce and have not been synthesised, hampering policy implementation. To fill this gap, we compared pollinator‐promoting interventions (treatment) with conventionally managed (control) sites regarding vegetation, floral resources, and pollinators. Our synthesis investigated 1051 sampling sites with different interventions (abandonment, extensive mowing, flower sowing, and combined practices) and habitats (parks, grasslands, road verges, private and public gardens) from 28 European datasets at pooled‐ and study‐levels. Urban pollinator‐promoting interventions generally benefited plants and pollinators with taxon, intervention, habitat, and spatio‐temporal specific differences. Pooled analyses showed mostly positive and never negative treatment effects, while study‐level details described primarily positive and neutral but rarely negative effects. Bumblebees and butterflies benefited most from the interventions. Some effects were stronger for interventions involving flower sowing, interventions occurring in road verges, and interventions located in Northwestern Europe. Although regulations, guidelines, and monitoring are improving, knowledge gaps remain for some pollinator taxa (e.g., beetles), regions (e.g., Mediterranean), and novel interventions (e.g., for ground‐nesting insects). Further collaborative studies from around the world could help cities bring people, plants, and pollinators together by creating resilient, multi‐functional urban spaces
Opinion of the French Agency for Food, Environmental and Occupational Health & Safety (ANSES) on the risks to human health associated with the proliferation of Ostreopsis spp. on the Basque coast
No full textN/AInternational audienceIn France, the presence of marine microalgae of the genus Ostreopsis has been identified repeatedly on the Mediterranean coast for several years, whereas on the French Basque coasts its presence is much more recent. In the summers of 2021 and 2022, major Ostreopsis flowering episodes were reported on the Basque coast, resulting in several hundred cases of intoxication among holidaymakers and residents. The main route of human exposure is inhalation of aerosols, although it is not yet known whether the agents responsible for poisoning are Ostreopsis cells, cell debris, known toxins produced by Ostreopsis, or other as yet unidentified compounds. Other routes of exposure (dermal contact, eye contact, ingestion of contaminated water or seafood) are also possible. Poisoning is manifested through various signs and symptoms, occurring within 48 hours of exposure (Neurosensory and neurological, respiratory, dermal and digestive). This document presents the opinion of the French Agency for Food, Environmental and Occupational Health & Safety (ANSES), established from the work of its WATER and ERCA Expert Committees. ANSES received a request from the Directorate General for Health (DGS) and the Directorate General for Food (DGAL) to update knowledge about Ostreopsis that had been reported in the Agency's opinions from 2007 and 2008 (ANSES, 2007 and 2008), and draw up specific recommendations for managing Ostreopsis proliferation on the Basque coast. The literature review conducted as part of this expert appraisal revealed that knowledge about the genus Ostreopsis (diversity, biology, ecology, toxins produced) is still too fragmentary to characterise the hazard and risk to human health. Nevertheless to help local authorities affected by Ostreopsis blooms, Agency proposes a surveillance and quality monitoring strategy based on collaboration between site managers and the regional health agencies (ARSs), applicable to sites currently subject to bathing water quality monitoring and water sports sites that meet the conditions below
Widening exposome exploration with a novel multiplexed HRMS analytical approach : a case study on pesticide internal exposure
No full textInternational audienceIntroduction : Human exposure to food and environmental chemical contaminants including pesticides is generally assessed by indirect (e.g. questionnaires) and/or targeted methods focusing on a limited number of selected compounds. These methods often require a large amount of sample for analyses as complete and sensitive as possible. Thus, human health risks associated with multi-exposure to complex mixtures currently remain underexplored. Based on the exposomics concept and previous studies (1,2), we propose an innovative global chemical profiling approach integrating three complementary HRMS platforms (LC-HILIC-HRMS, LC-C18-HRMS and GC-HRMS), for capturing an extended range of contaminants and related metabolites from a unique urine sample.Methods : Fractionation of reduced-volume urine samples (0.5 mL) was preformed using Strata-X® SPE cartridges. HRMS experiments were conducted on GC-Orbitrap q-Exactive (GC-MS), Sciex X-500-R Q-ToF (C18-LC-MS) and LTQ-Orbitrap XL (HILIC-LC-MS) instruments. Data processing was carried out on both commercial and open source softwares (Trace Finder, W4M, Scannotation, …). A set of 187 standard compounds (parent compounds + metabolites) covering both a large range of molecular weights (72 g/mol1000) from a single sample, provides valuable data for assessing associations with health endpoints for epidemiological studies. Novelty : innovative multiplexed HRMS methodology for wide exposomics from a unique sample. References1 E. L. Jamin et al. Anal. Bioanal. Chem., 2014, 406, 1149-1161.2 N. Bonvallot et al. Sci. Tot. Environ., 2021, 786, 147499.3 T. Moufawad et al. In preparatio
Exposure to toxic trace metals is negatively associated with testis mass in wild male roe deer
No full textInternational audienceAlthough trace metal toxicity has been extensively studied in laboratory settings, its long-term effects on wildlife are poorly understood. Most wild animals are likely to be exposed to low doses of trace metals throughout their lives; however, whether such chronic exposure affects fitness-related traits in natural populations remains to be investigated. In this study, we tested the relationships between trace metal burden and sex hormones, primary and secondary sexual traits in wild male roe deer. Using samples collected from 71 hunted males, we measured the hair and liver concentrations of various toxic trace metals, faecal testosterone metabolites (FTM), testis mass and antler length. We focused on cadmium (Cd), cobalt (Co), nickel (Ni) and lead (Pb) in roe deer tissues. Using linear (mixed effects) models, we found that Cd and, to a lesser extent, Co concentrations in the liver, but not in hair, were negatively associated with absolute testicular mass, a proxy of sperm production. However, metal burden, measured in either the liver or hair, was not related to antler length or FTM levels, despite their respective roles in male competitiveness for access to females and the underlying adjustments for seasonal breeding. Hence, our findings highlight the consequences of exposure to Cd and Co on male testicular function in a wild ungulate. Any alteration in male competitiveness for fertilization is expected to have lasting fitness consequences, which could subsequently alter population dynamics
Surface grain-size mapping of braided channels from SfM photogrammetry
No full textInternational audienceBraided channels are known as fluvial systems with a high heterogeneity of physical conditions, resulting from particularly active interacting processes of coarse sediment sorting and transport. This in turn generates a complex mosaic of terrestrial and aquatic habitats, supporting an exceptional biodiversity. However, documenting this physical heterogeneity is challenging, notably the textural variability in these rivers, which is particularly strong. Distributed and continuous grain-size maps of braided channels are notably of great interest in this regard. In this study, high-resolution imagery obtained from uncrewed aerial vehicles (UAVs) equipped for direct georeferencing was used to produce 3D point clouds (structure from motion photogrammetry, SfM), from which surface grain size has been inferred. A set of 12 braided river reaches located in the southeast of France was used to calibrate a roughness-based grain-size proxy (indirect measurement), and this proxy was used for the production of distributed grain-size maps. The calibration curve can be used to determine the surface median grain size with an independent error of 5 mm (14 % of relative error). The resampling procedure shows a good transferability of the calibration, with a residual prediction error ranging from 5 % to 17.5 %. Reach-averaged median grain sizes extracted from roughness-based grain-size maps were in very good agreement with values collected in the field from intensive grain-size samplings (differences of less than 5 %). Some examples of morpho-sedimentary signatures derived from these maps are provided. They notably show a systematic altimetric gradient of the maximum grain size of bars, which is interpreted as a hydrological imprint and should be better integrated into conceptual models of grain-size patchiness developed for these rivers
What evidence exists on the impacts of artificial light on terrestrial non-flying mammals native to Europe? A systematic map and a narrative review
No full textInternational audienceIntroductionNowadays, light pollution due to the multiplication of outdoor lightings has become a worldwide disturbance for many species. A large amount of scientific literature shows that this sensory stressor has adverse effects on several taxa. However, existing reviews tend to conclude a lack of primary research on terrestrial non-flying mammals even if these organisms are highly nocturnal and frequently exposed to artificial light.MethodsTo have a more accurate overview on the available literature, we followed the guidelines proposed by the Collaboration for Environmental Evidence to perform a comprehensive evidence synthesis, focusing on the 186 terrestrial non-flying mammal species native to Europe. We searched 2 academic databases and Google Scholar for scientific and grey literature on the impacts of artificial light. We exported 6624 citations and screened 4866 articles on titles, abstracts, and then full-texts. We coded variables and extracted results for all the included studies to build a systematic database and we synthetized the data.ResultsWe collected 48 articles on 22 mammal species across 12 families, revealing a more substantial knowledge than expected. composed of 448 study units. We identified four main research hotspots that address different questions: 1/ impacts of manipulating the photoperiod; 2/ impacts of ex-situ artificial light on small mammals; 3/ impacts of in-situ outdoor lightings; 4/ impacts of global light pollution (sky glow). We described the results of the included studies in a narrative review to provide a factual overview of the findings.DiscussionThese initial results draw detrimental impacts of ALAN on circadian rhythm, behaviour, foraging or movements and ultimately occurrence, which are consistent with available literature on moonlight influence or ALAN effects on other taxa. Hence, we call for much more attention to be paid to wild terrestrial non-flying mammals in relation to this key anthropogenic driver
Impact of Sentinel-2 light extinction data on lake temperature profile simulations in the 1D hydrodynamic General Lake Model
No full textInternational audienc
Response of freshwater periphyton to pesticides, their mixture and transformation products: New insight from untargeted metametabolomics
No full textInternational audiencePesticides are widely used in agriculture and ends up into aquatic environment where they may affect exposed organisms. All along this transfer process from field to river, pesticides can be degraded by abiotic processes and generate transformation products (TPs) for which the identity and the ecotoxicity is mostly unknown. Among these organisms, aquatic periphytons are complex assemblages of microorganisms with a short life cycle (e.g. microalgae, bacteria, etc.) playing a key role in aquatic ecosystems (e.g. primary production). Thus, they are relevant to investigate the impact of chemical contamination at the community level. Despite increasing knowledge on the impact of chemical stress, there is a still of paucity information about the effect of mixture of pesticides and their TPs on these communities. To such an end, metabolomics appears as choice method by prodiving a comprehensive picture of the molecular phenotype. In this context, our study aims to evaluate the toxicity of the herbicide terbuthylazine (TBA) and its transformation products on periphyton through the implementation of a multi-descriptors approach. To do so, periphyton was exposed during 4 weeks to TBA, to one of its commercially available degradation product (TBA-desethyl), both at 5 and 150 µg/L and to weathered TBA (wTBA, homemade by photodegradation from TBA at 5 and 150 µg/L). To enhance the environmental realism, periphyton was exposed to TBA-desethyl in mixture with 2 ubiquitous contaminants, glyphosate and AMPA (GA) at environmental concentrations (0.1 and 0.3 µg/L, respectively). A control (without any contaminants) and GA conditions were also set-up to allow comparison between conditions. First, most descriptors (photosynthetic yield, biomass, heterotrophic enzymatic activities) were strongly affected by TBA and not or slightly by the transformation products, being the TBA-desethyl or the wTBA or the mixture with glyphosate. Controversy, multivariate analyses (PCA and HCA) showed discrepancies in the metabolomics profile between each conditions, TBA 150µg/L being the most discriminated while both 5 and 150 µg/L of TBA-desethyl and wTBA were also separated from the controls. Nevertheless, all conditions with GA had a similar metametabolome profile suggesting no mixture effect. Overall, this study confirms the higher sensitivity of the metametabolome to micropollutants and so its relevance to highlight potential impact of TPs and mixtures on aquatic microbial communities