HAL Collection UNC (Univ. de la Nouvelle Calédonie)
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Tannin with sodium carbonate: A single additive for poured earth concrete with tropical soils
No full textInternational audienceBuilding sustainable earth construction to replace cement concrete is a major challenge in fast-developing tropical regions. Poured earth, shaped like concrete, offers a cost-effective and eco-friendly alternative. Poured earth usually relies on industrial dispersants and hydraulic binders to fluidify and solidify the soil paste. However, these additives strongly increase environmental costs. Recent studies have highlighted the potential of tannins, which are organic extracts from wood, as an eco-friendly alternative. In particular, tannins combined with iron oxides can fluidify soils at an elevated pH, and chemical reactions between tannins and iron oxides lead to rapid solidification, enabling rapid unmolding and improving water resistance. Tropical soils naturally have a high iron oxide content. This study investigated whether tannins could react with the iron oxides naturally present in tropical soil and be used as a single additive for poured earth. Optimal reactions between soils, tannins and iron oxides require an elevated soil pH, and tannins were combined with sodium carbonate (Na2CO3), a low-cost, eco-friendly alkali. Mortars prepared with different dosages of tannin+Na2CO3 were tested and compared to the industrial dispersant sodium hexametaphosphate (NaHMP), using three tropical soils from French Guiana. Results showed that both tannin+Na2CO3 and NaHMP could fluidify the three soils, improved mechanical strength and water resistance, and reduced initial water content and shrinkage. However, tannin+Na2CO3 induced faster solidification, which was attributed to the formation of ferric tannate observed by infrared spectroscopy (ATR-FTIR). This study paves the way for designing poured earth with tropical soil using a single, largely bio-sourced additive: tannin+Na2CO3
First release of the European marine omics biodiversity observation network (EMO BON) shotgun metagenomics data from water and sediment samples
No full textInternational audienceThe European Marine Omics Biodiversity Observation Network (EMO BON) is an initiative of the European Marine Biological Resource Centre (EMBRC) to establish a persistent genomic observatory amongst designated European coastal marine sites, sharing the same protocols for sampling and data curation. Environmental samples are collected from the water column and, at some sites, soft sediments and hard substrates (Autonomous Reef Monitoring Structures - ARMS), together with a set of mandatory and discretionary metadata (including Essential Ocean Variables - EOVs). Samples are collected following standardised protocols at regular and specified intervals and sequenced in large six-monthly batches at a centralised sequencing facility. The use of standard operating procedures (SOPs) during data collection, library preparation and sequencing aims to provide uniformity amongst the data collected from the sites. Coupled with strict adherence to open and FAIR (Findable, Accessible, Interoperable, Reusable) data principles, this ensures maximum comparability amongst samples and enhances reusability and interoperability of the data with other data sources. The observatory network was launched in June 2021, when the first sampling campaign took place
Vulnérabilité du patrimoine récifal : réflexions sur la 3ème édition de l’école thématique interdisciplinaire du Sud-ouest de l’Océan Indien (VulPaRe 2024).
No full textSince 2014, the French National Research Institute for Sustainable Development (IRD) has hosted three interdisciplinary thematic schools on the vulnerability of the reef heritage (VulPaRe) in the Western Indian Ocean. Taking a sustainability science approach, the schools aim to build capacity, facilitate knowledge transfer, and foster collaboration among a variety of stakeholders involved in research and the governance of coastal resources. The latest VulPaRe school highlighted 1) the need to strengthen the role of social sciences in interdisciplinary studies, 2) the opportunities and threats of market-based mechanisms integrating conservation and ecological restoration, and 3) concerns of justice on the access to common resources. An improvement of this educational process would be to provide more guidance for dialogues with decision makers in these reef areas.L’institut de Recherche pour le Développement (IRD) a initié un projet d’école thématique sur le sujet de la vulnérabilité du patrimoine récifal (VulPaRe). Cette troisième édition, qui s’est déroulée en juin 2024 aux Seychelles, est axée sur l’interdisciplinarité. L’école a pour objectif de faciliter la communication et d’encourager à la collaboration dans la gouvernance et la durabilité du management des ressources côtières de l’océan Indien. Elle a souligné, 1) la nécessité de renforcer le rôle des sciences sociales dans les études interdisciplinaires visant à informer la gouvernance, 2) les atouts et dangers des mécanismes de conservation et de restauration écologique et 3) les préoccupations de justice sur l’accès aux ressources communes. L'école a offert une plateforme efficace aux acteurs non politisés pour discuter des problèmes régionaux actuels et des solutions. Une amélioration de ce processus pédagogique serait de parvenir à fournir davantage de conseils pour nourrir des dialogues avec les décideurs chargés de décider pour ces zones récifales
Biological Responses to Ocean Acidification Are Changing the Global Ocean Carbon Cycle
No full textInternational audienceIncreased oceanic uptake of CO 2 due to rising anthropogenic emissions has caused lowered pH levels (ocean acidification) that are hypothesized to diminish biotic calcification and reduce the export of total alkalinity (A T ) as carbonate minerals from the surface ocean or their burial in coastal sediments. This "CO 2biotic calcification feedback" is a negative feedback on atmospheric CO 2 , as elevated levels of surface A T increase the ocean's capacity to uptake CO 2 . We detect signatures of this feedback in the global ocean for the first time using repeat hydrographic measurements and seawater property prediction algorithms. Over the course of the past 30 years, we find an increase in global surface A T of 0.072 ± 0.023 μmol kg 1 yr 1 , which would have caused approximately 20 Tmol of additional A T to accumulate in the surface ocean. This finding suggests that anthropogenic CO 2 emissions are measurably perturbing the cycling of carbon on a planetary scale by disrupting biological patterns. More observations of A T would be required to understand the effects of this feedback on a regional basis and to fully characterize its potential to reduce the efficiency of marine carbon dioxide removal technology.</div
Avifaune marine de l'île Walpole (parc naturel de la mer de Corail) : compilation des données acquises lors de missions ornithologiques ponctuelles, de 1973 à 2021
No full textThe aim of this report is to compile relevant ornithological data acquired during naturalist expeditions to Walpole Island since the 1970s. This information concerns the estimated population sizes of the species, their breeding phenology and the habitats used for nesting. The seabirds observed breeding on Walpole Island are the yellow-billed tropicbird, the red-tailed tropicbird, the brown booby, the red-footed booby, the lesser frigatebird, the great frigatebird, the black noddy, the brown noddy and the white tern. The black-winged petrel almost certainly breeds on the island. This report constitutes the first open-access database on the marine avifauna of Wal-pole Island.Le présent rapport a pour objectif de compiler les données ornithologiques pertinentes acquises au cours des missions naturalistes effectuées sur l'île Walpole depuis les années 1970. Ces informations concernent les tailles estimées des populations des espèces présentes, la phénologie de leur reproduction et les habitats utilisés pour la nidification. Les oiseaux marins observés en reproduction sur cette île sont le phaéton à bec jaune, le phaéton à brins rouges, le fou brun, le fou à pieds rouges, la frégate ariel, la frégate du Pacifique, le noddi noir, le noddi brun et la gygis blanche. La reproduction du pétrel à ailes noires est quasi-certaine. Le présent rapport constitue la première base de connaissances en accès ouvert sur l'avifaune marine de l'île Walpole
Passé, Présent et Avenir à Mayotte : contribution à l’étude des temporalités en contexte pluriculturel
No full textInternational audience« Mayotte entre passé, présent et avenir » est le titre donné à ce colloque qui interroge d’emblée la linéarité a priori du temps et des temporalités dans le contexte territorial Mahorais. Le territoire de Mayotte fait se rencontrer des systèmes de connaissances culturelles des mondes de façon intriquée (Lambek, 2018), entre islam, cultures africaines, malgaches, françaises et arabes, ce qui participe parfois de certaines sources de confusion, voire de crispation, quant à la définition d’un objet partagé comme le temps. Au travers d’une recherche théorique sur le concept de temps prenant appui sur divers auteurs tels que Kosseleck (1990), Hartog (2003, 2020, 2022), ou encore Chesneaux (1996), en passant par le concept antique de Chronos, nous proposons un modèle à vocation heuristique, baptisé « chronoglyphe » que nous mobilisons pour l’analyse des temporalités selon une approche contrastive (Yllera, 2001) en contexte pluriculturel. Après avoir présenté notre modèle, nous en proposerons une mise en application dans le contexte mahorais, au travers du concept d’umri tel que décrit par Blanchy (1988), et nous proposerons une discussion sur les conséquences contemporaines de cette conception temporelle
Suivi spatio-temporel des herbiers de la Réunion par imagerie satellitaire Pléiades sur la période entre 2013 et 2023
No full textCette cartographie spatio-temporelle a été réalisée dans le cadre du projet SCO-BioEOS. La méthodologie utilisée pour ce suivi des herbiers est réalisée par une classification supervisée semi-automatique via un outil interactif basé sur l’algorithme du plus proche voisin. Les images utilisées (50 cm de résolution), acquises entre 2013 et 2023, sont issues de fusion entre les images multispctrales et le canal panchromatique pour chacune des dates. Ces couches sont également utilisées pour entrainer un modèle de classification automatique de type « Deep Learning » pour la détection automatique des herbiers à partir de scènes Pléiades.La cartographie des herbiers de La Réunion a été réalisée dans le cadre du projet SCO BioEOS, financé par le CNES et la DEAL Réunion. Elle est le résultat d’une classification-semi-automatique d’une série temporelle d’images Pléiades entre 2013 et 2023. L’objectif est le suivi de la dynamique spatio-temporel de cet habitat vulnérable en vue de l’élaboration d’indicateurs en appui à la gestion
Cartographier les variables essentielles de biodiversité côtière par imagerie satellite multi et hyperspectrale : Projet SCO-BioEOS
No full textInternational audienceSoutenu par le Centre national d'études spatiales (CNES) et labellisé par l'Observatoire spatial du climat (SCO), le projet BioEOS vise à développer des outils d'observation pour caractériser la dynamique spatiotemporelle de la biodiversité côtière. Cette initiative permettra de cartographier les changements et de produire des indicateurs opérationnels en soutien à la conservation et à la restauration dans les Aires marines protégées (AMP). Le projet s'appuie principalement sur des séries temporelles d’images provenant de systèmes satellitaires multispectraux (Pléiades, Sentinel-2, Vénus) et hyperspectraux (EnMAP, PRIS-MA). Un ensemble de métriques, proxy de la biodiversité, sont extraites grâce à l’intégration d'algorithmes à SRL (Scientific Readiness Level) élevés, largement utilisés par la communauté scientifique. Cette approche permet de générer des informations sur la bathymétrie, l'abondance des types d'habitats/fonds et les estimations des propriétés de la colonne d'eau. Les récifs coralliens et les herbiers marins de la région sud-ouest de l'océan Indien (La Réunion, Mayotte, Glorieuses et Bassas da India) sont les premiers écosystèmes ciblés pour cette expérimentation. Nous proposons de présenter les principales avancées d'un démonstrateur fournissant des variables essentielles contribuant à diverses utilisations finales à travers quatre cas d'utilisation distincts. De plus, nous discuterons des points forts et des limites des systèmes satellitaires employés, à la lumière des objectifs initiaux fixés
Shining a Light on Daytime Coral Spawning Synchrony Across Oceans
No full textInternational audienceAimThe variety of coral taxa and environmental cues triggering broadcast spawning gave rise to contrasting theories about coral reproduction synchrony. Here, we shine a new light on this synchrony across oceans by highlighting how environmental cues modulate spawning time at various spatial scales in an understudied yet abundant gonochoric species. LocationSouth Indian and Pacific Oceans. Time Period2014–2023. Major Taxa StudiedPorites rus . MethodsPorites rus daytime spawning was investigated using a non‐invasive citizen science approach (> 300 voluntary observers) at colony, reef, island and ocean scales. Spawning time was recorded between 2014 and 2023 at a total of 104 reef locations from 15 islands in three countries and multiple depths across the Indian and Pacific Oceans. Statistical models were employed to assess the relationships between spawning time and depth, light and sea surface temperature at different spatial scales, and in both male and female colonies. ResultsSpawning occurred synchronously for colonies located a few meters to > 15,000 km apart, monthly 5 days after full moon over an extended, uninterrupted period from October to April. Strong linear relationships between depth, light, water temperature and spawning time after sunrise held at the different spatial scales for both males and females, which spawned ca. 20 min apart. Interestingly, single colonies spawned across consecutive days and months. Main ConclusionsThe largest data set for a daytime coral species compiled here allows extremely accurate predictions of P. rus spawning months, days and time (minute‐level precision) at different locations and depths in the Southern Hemisphere, facilitating field observations and experiments. Previously underexplored, the highly effective reproductive strategy of P. rus may explain its broad distribution and persistence in stressed environments, positioning it as an invaluable model organism for studying the physiological and genetic processes driving behavioural synchrony and biological rhythms across interconnected biogeographical regions
Decrypting the Breeding Biology of the Elusive and Declining Tahiti Petrel <i>Pseudobulweria rostrata</i>
No full textInternational audienceAmong procellariids, the Tahiti Petrel Pseudobulweria rostrata is one of the most endangered and least known species. Its global populations are declining, yet demographic and ecological studies remain scarce. Understanding the breeding cycle and behavior of Tahiti Petrel adults and chicks is essential to develop effective protection measures. To address this knowledge gap, Tahiti Petrel colonies of various sizes were studied at three sites in New Caledonia, with extensive sampling at two main sites and limited sampling at a third. A total of 157 burrows were monitored for up to two years using endoscopic cameras and camera traps. This allowed the depiction of the breeding phenology, reproductive success, frequency of adult nest visits, chick behavior, first emergence, and fledging dates. During the study, 75% of the identified burrows were visited by Tahiti Petrels. Egg-laying peaked in December but occurred year-round, indicating aseasonal breeding by Tahiti Petrels in New Caledonia. The average breeding cycle was 329 ± 11.6 days, including an average incubation period of 55.7 ± 0.9 days and an average chick-rearing period of 110.7 ± 5.6 days. Parents visited nests every 1.3 days on average during chick-rearing. After the chick’s first emergence, which typically occurred 31 days before fledging, adult visitation decreased. Chicks did not show defensive behavior against predators, and most chicks fledged after nine days without feeding. Breeding success was 50% at a predator-free site and 32% at a site with invasive predators. These findings suggest high sensitivity to disturbance and depredation, contributing to the species’ decline in New Caledonia and elsewhere in the world. Together with previous studies conducted in New Caledonia, these results provide crucial information for the implementation of adapted conservation measures for this declining species