HAL Collection UNC (Univ. de la Nouvelle Calédonie)
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Sargassum leachate initially inhibits then stimulates phytoplankton growth in coral reef waters
No full textInternational audienceMassive Sargassum accumulations in the Atlantic form the Great Atlantic Sargassum Belt, which fuels recurrent coastal inundation events that disrupt ecosystems by reducing light availability for phytoplankton and enriching nearshore waters with nutrients released during decomposition. This study examined the short-term effects of decaying Sargassum leachate on phytoplankton productivity and growth in Guadeloupe’s coral reef ecosystems using several photosynthesis measurements based on fluorescence and 13C. A range of leachate concentrations were applied, under controlled conditions, to a natural phytoplankton community. The study revealed two major effects of Sargassum leachate on phytoplankton. First, leachate at concentrations ≥1 % initially inhibited photosynthesis and growth up to Day 2, likely due to allelopathic substances such as polyphenols. This was evidenced by near-zero Fv/Fm values and disrupted electron transport in PSII. By Day 3, these inhibitory effectsdiminished, suggesting degradation of labile inhibitory compounds or community modification. Second, from Day 3 onward, leachate addition stimulated phytoplankton growth, as seen in increased biomass, primary production (JVIImax), and carbon fixation. This nutrient-driven response was accompanied by reduced C/Chl a ratios and improved photosynthetic efficiency (lower Фe,C values), indicating alleviation of nutrient limitations, particularly nitrogen and phosphorus. These findings underscore the dual role of Sargassum leachate: an initial suppressive impact through allelopathy and a subsequent nutrient enrichment effect driving phytoplankton blooms. Such dynamics highlight the significant and complex influence of Sargassum strandings, combining ecological stress with nutrient-driven productivity changes
L’accueil de nouveau-nés évacués de Mayotte : tensions et redéfinition des pratiques et identités professionnelles en néonatologie à La Réunion
No full textInternational audienceDue to overcrowding at the neonatal unit in Mayotte, newborn babies are sometimes transferred to hospitals on Reunion Island, another French overseas territory. These transfers are by air via the EVASAN medical evacuation system. This article is based on research conducted in a Reunion neonatology ward that receives transferred newborns, accompanied or not by their mothers. The article explores the impact on the practices and professional identities of nurses and nursery auxiliaries. These new patients arrive in a ward with limited resources, resulting in an increased workload. The presence of the mothers is deemed necessary for the well-being of the children. However, their being there introduces a social dimension to the hospital. This creates ethical tensions and blurs professional boundaries within a context where these patients are not considered a priority. It is also assumed that their care will be temporary.En raison de la saturation du service de néonatologie du centre hospitalier de Mayotte, il arrive que des nouveau-nés de parents résidant à Mayotte soient transférés dans un centre hospitalier de La Réunion, par le dispositif d’évacuation sanitaire EVASAN. Cet article repose sur une recherche de terrain dans un service de néonatologie de La Réunion. Il explore les effets de l’accueil de ces nouveau-nés évacués, accompagnés ou non de leur mère, sur les pratiques et les identités professionnelles des infirmières et auxiliaires puéricultrices. L’arrivée de ces nouveaux publics, dans un service peu outillé pour les accueillir dans de bonnes conditions, se traduit par une surcharge de travail. La présence des mères, si elle est jugée nécessaire pour le bien-être de l’enfant, fait entrer la question du social à l’hôpital, engendrant tensions éthiques et brouillage des rôles professionnels, dans un contexte où ces publics apparaissent non prioritaires et où leur accueil est perçu comme provisoire
Observation-only deep learning for gappy satellite-derived ocean colour data using 4DVarNet
No full textInternational audienceMonitoring optical properties of coastal and open ocean waters is crucial to assessing the health of marine ecosystems. Deep learning offers a promising approach to address these ecosystem dynamics, especially in scenarios where gapfree ground-truth data is lacking, which poses a challenge for designing effective training frameworks. Using an advanced neural variational data assimilation scheme (called 4DVarNet), we introduce a comprehensive training framework designed to effectively train directly on gappy data sets. Using the Mediterranean Sea as a case study, our experiments not only highlight the high performance of the chosen neural network in reconstructing gap-free images from gappy datasets but also demonstrate its superior performance over state-of-the-art algorithms such as DInEOF and end-to-end neural mapping schemes based CNN or UNet architectures.</div
Drivers of fish diversity and size spectra across lagoonal habitats of the Toliara reef system (SW Madagascar)
No full textInternational audienceSize-spectra and taxonomic diversity are important indicators to study the dynamics of communities and to inform conservation in aquatic ecosystems. To date, few studies aimed at modelling the distribution of reef fish diversity at small spatial scales (∼10 km) have been done. Based on a one-year fish sampling using trawl nets, we described and modeled the distribution of fish diversity and their size spectra across various coastal habitats in the Toliara reef system (SW Madagascar). Our data revealed a significant spatial and seasonal change of taxonomic diversity. Beta-diversity was mainly driven by species turnover with up to 75 %, indicating the important conservation value of the sampled sites. Fish size spectra slope emphasized the high dominance of small-sized fish on the sites close to the shoreline indicating their potential nursery zones. By combining environmental and geographic data with the use of the machine learning algorithm Random Forest, we demonstrated the geographic position of sites and associated habitat features were the foremost drivers of alpha-diversity and size spectra patterns (50–64 % of variation). The use of Generalized Dissimilarity Models revealed sediment cover was the main predictor of species turnover patterns (62 % of explained variation), with a rapid increase of species replacement within the first 2 km from the coast. Beyond a confirmation of the role of habitat features on biodiversity, our study emphasized the importance of distance to the shoreline on the distribution of fish diversity across the lagoon. This unexpected driver is discussed in the light of various anthropogenic factors including fisheries and sedimentation
Contact‐ and Water‐Mediated Interactions With an Allelopathic Macroalga Drive Distinct Coral Microbiome and Metabolome
No full textInternational audienceMacroalgal proliferation constitutes a major threat to coral reef resilience. Macroalgae can affect corals by altering their microbiome and metabolome. However, our understanding of the spatial scale of these effects and the influence of environmental factors is limited. We conducted a manipulative field experiment to investigate how interaction types (direct contact and close proximity) with the allelopathic macroalga Dictyota bartayresiana and prevailing water current influence the microbiome and metabolome of the coral Pocillopora acuta and its near‐surface seawater. Coral tissue damage was spatially constrained to the algal contact zone. Direct contact caused significant increases in harmful bacteria at the expense of beneficial ones in side coral fragments. Non‐significant changes were observed within the microbiome of apex fragments, suggesting a resistance of the coral holobiont to colony‐wide microbial colonisation. The coral metabolome responded to both algal contact and proximity. We detected several compounds potentially relevant for oxidative stress mitigation and coral defence. This metabolomic response was similar between apex and side fragments, supportive of a colony‐wide metabolomic response. In the near‐surface coral seawater, only a microbial response to algal contact was detected. We conclude that coral holobionts are capable of colony‐wide metabolomic responses to maintain homeostasis against macroalgal competitors
Deciphering the molecular mechanisms of oyster resistance to Pacific Oyster Mortality Syndrome (POMS) disease induced by high temperatures
No full textInternational audienceClimate change and rising temperatures are frequently cited as key factors in the emergence of diseases. While the increase in temperature can alter host immunity, influence pathogen virulence, and change the geographic distribution of vectors and their associated pathogens, few studies have investigated the impact of temperature variations on the molecular mechanisms controlling disease permissiveness. The present study addresses this question on a panzootic and polymicrobial disease, the Pacific Oyster Mortality Syndrome (POMS). POMS, initiated by the herpesvirus OsHV-1 μVar, affects juveniles of Magallana gigas, which is the most widely cultured oyster species in the world. In our study, two full-sib families were exposed to the disease under permissive (23 °C) and non-permissive (30 °C) conditions. Using an integrative multi-omics approach, we demonstrate that high temperature has a dual effect on oysters (1) inducing a metabolic reprogramming, creating a sub-optimal metabolic environment for viral infection and thereby limiting POMS development, and (2) enhancing the host's antiviral immune capabilities, both at a baseline level and in response to infection. Overall, these responses triggered at elevated temperature improve oyster survival against POMS. Our study showed that temperature exerts complex effects on host-pathogen interactions; and molecular-level mechanistic approaches are crucial to thoroughly understand and accurately assess how temperature changes can influence epidemiological risk
Mesures anthropométriques, réponses aux questionnaires et données de condition physique obtenues dans le cadre du projet scientifique : "Cultures et comportements alimentaires de la jeunesse dans les pays francophones du Pacifique au XXIème siècle : exemple de la Nouvelle-Calédonie" (version anonymisée)
No full textDeposit containing the anonymized dataset and supplementary files related to the scientific project: "Eating cultures and behaviors of young people in French-speaking Pacific countries in the 21st century: the example of New Caledonia", translation of "Cultures et comportements alimentaires de la jeunesse dans les pays francophones du Pacifique au XXIème siècle: exemple de la Nouvelle-Calédonie".Measurements and responses provided by the participants envolved in the scientific project entitled "Cultures et comportements alimentaires de la jeunesse dans les pays francophones du Pacifique au XXIème siècle: exemple de la Nouvelle-Calédonie" [en: "Eating cultures and behaviors of young people in French-speaking Pacific countries in the 21st century: the example of New Caledonia"]. This anonymized dataset contains ten files. Six files are data files in various formats and four are like supplementary files that describe the data content and the tools used: _ anonymizedData_en_2025.xlsx: xlsx file with the participants' information, measurements and answers in English _ anonymizedData_en_2025.csv: csv file with the participants' information, measurements and answers in English _ anonymizedData_fr_2025.xlsx: xlsx file with the participants' information, measurements and answers in French _ anonymizedData_fr_2025.csv: csv file with the participants' information, measurements and answers in French _ anonymizedData_code_en_2025.xlsx: xlsx file with coded answers based on the English version file (i.e., anonymizedData_en_2025.xlsx) _ anonymizedData_code_en_2025.csv: csv file with coded answers based on the English version file (i.e., anonymizedData_en_2025.xlsx) _ Food cultures_dataContentDescription_en.pdf: pdf file describing the frequencies for social and weight status information, and for the questionnaire responses through various tables and graphs _ Food cultures_DataFileDescription_anonymized.pdf: pdf file describing the content of the data files translated in English _ Food cultures_questionnaireCodeBook_en.pdf: pdf file describing each item (question, options, and code) of the questionnaires (translated in English) used for data collection _ Food cultures_questionnaireCodeBook_fr.pdf: pdf file describing each item (question, options, and code) of the questionnaires (in French) used for data collection Participant characteristics: 10 to 17 years old students (n = 1062) in secondary school Year of the study: 2018 - 2019 Place of the study: New Caledonia The current dataset is anonymized. A restricted non-anonymized version is available also on Zenodo: Wattelez, G., Frayon, S., Paufique, É., Le Roux, P.-Y., Nedjar-Guerre, A., Ponidja, S., Zongo, P., Serra-Mallol, C., Wacalie, F., Caillaud, C., & Galy, O. (2025). Anthropometric measurements, questionnaire responses and fitness data collected during the scientific project: "Eating cultures and behaviors of young people in French-speaking Pacific countries in the 21st century: the example of New Caledonia" (non-anonymized version) (2.0.0) [Data set]. Zenodo. https://doi.org/10.5281/zenodo.16828868
Health literacy of adolescents’ responses to a workshop focusing on food, nutrition, climate change and digital technology solutions in Oceania: a multi-site pilot study in Vanuatu
No full textInternational audienceBackgroundNon-communicable diseases (NCD) have become the leading cause of premature death and disability in the Pacific region, with the development of health literacy an important factor for the prevention and control of NCD. Health literacy is an important lifelong asset that can be developed in adolescents through engagement in schooling and curriculum. The aim of this study was to explore Ni-Van adolescents' health literacy knowledge and capabilities regarding food and nutrition, climate change and digital technology solutions.MethodsTwo Ni-Van schools participated in the study (one urban (School A) and one rural school (School B)), with 44 students (68% female) comprising 14 small groups participating in one workshop and booklet activities in April 2023. The 14 workshop booklet responses were deductively analysed using Nutbeam’s health literacy hierarchy.ResultsSchool A’s booklet responses showed that interactive health literacy responses were dominant (54%), followed by functional (34%) and critical learning activities (12%), whereas School B’s responses showed that functional health literacy responses were dominant (65%), followed by interactive (28%) and critical (5%).ConclusionThe findings show that students in both schools were less likely to engage in critical, compared with functional and interactive health literacy levels. This is an important consideration for future workshops, as well as curriculum and teacher training in Vanuatu, as Vanuatu (and other PICTs) are more susceptible to the effects of climate change and food sustainability issues.. Without a focus on developing critical health literacy knowledge and capabilities throughout the schooling years, this is a missed opportunity to create enabling environments that reduce youth exposures to NCD risk factors
