HAL Portal UPF (Université de la Polynésie française)
Not a member yet
3802 research outputs found
Sort by
Ecological Specialisation of Reef Fishes Peaks in Global Biodiversity Hotspots
No full textInternational audienceABSTRACT Aim The role of ecological specialisation in shaping biogeographic and evolutionary patterns remains unresolved. To date, few studies have quantitatively examined consumer niche breadth at a global scale. We describe global biogeographic and diversification patterns of specialisation, measured using trophic and thermal niches, for a highly diverse assemblage of consumers: reef fishes. First, we investigated the confluence of specialisation with global biogeographic patterns in species richness and reef area. Then, we tested whether these patterns could be explained by differences in diversification rates and geographic ranges. Location Tropical reefs across the globe. Time Period Present. Major Taxa Studied Reef fishes. Methods To estimate trophic specialisation, we compiled a comprehensive dataset on reef fish trophic interactions from published gut content analyses, including dietary information for ~5000 individuals across 387 fish species. We used the geographic range of species and global temperature data to estimate thermal specialisation of reef fishes. We used distributional data and Bayesian Structural Equation Modelling to test for the correlation between biogeographic variables, species richness, and the prevalence of trophic or thermal specialisation in reef fish assemblages. Moreover, we used linear models to test for a correlation between reef fish diversification rates, geographic range, and their degree of trophic and thermal specialisation. Results Our analysis suggests that species richness is positively associated with trophic specialisation in reef fishes, with isolated and species‐depauperate communities supporting assemblages dominated by trophic and thermal generalists. We found no effect of trophic and thermal specialisation on diversification rates and geographic range at the species level. Main Conclusions Our findings indicate that specialisation is favoured in large, biodiversity‐rich regions, but specialists might show lower capacity for colonisation, with lower representation on smaller, isolated reefs. These results contribute to our understanding of the dynamics shaping fish biogeography on coral reefs
Marine heatwaves imperil emblematic reef fishes by altering the energetic landscape of coral reefs
No full textInternational audienceMarine heatwaves are increasingly common due to human‐induced climate change. Under prolonged thermal stress on coral reefs, corals can undergo bleaching, leading to mass coral mortality and large‐scale changes in benthic community composition. While coral mortality has clear, negative impacts on the body condition and populations of coral‐dependent fish species, the mechanisms that drive these changes remain poorly resolved. Specifically, little is known about the effects of coral bleaching on (1) the nutritional quality of corals, (2) nutrient acquisition in coral‐feeding butterflyfishes and (3) fish dietary selectivity and potential supplementary consumption of non‐coral prey. Here, we evaluate the response of obligate coral‐feeding butterflyfishes to a mass coral bleaching event in French Polynesia, which resulted in high coral mortality and a 50% decline in obligate corallivore density. We examine benthic and butterflyfish community composition over two decades, including a mass bleaching event in 2019 and multiple prior disturbances. We couple these data with surveys of butterflyfish feeding selectivity, high‐resolution molecular assays of gut contents and nutrient acquisition before, during and after the bleaching event. Contrary to previous studies, obligate corallivores did not strongly alter their feeding preferences for different coral genera in response to bleaching. They did not increase their consumption of non‐corals in response to coral mortality, and hard corals continued to dominate their diets (>90%). Instead, butterflyfishes targeted partially bleached corals that were likely releasing nutrient‐rich mucus, and they avoided fully bleached and dead corals that were likely nutrient‐depleted. Moreover, after bleaching, butterflyfishes exhibit reduced nitrogen assimilation, indicating that coral stress may adversely impact butterflyfish nutrient acquisition. Coupled with the increasing frequency of recurrent bleaching events, severe, long‐term nutritional impacts of coral bleaching on butterflyfish populations may jeopardize the persistence of coral‐feeding fishes in the future
Re-connecting ecosystems: Integrating coral reefs into monitoring of island restoration
No full textInternational audienceEcosystems are intrinsically linked, such that management actions in one ecosystem can influence adjacent ecosystems. However, adequate data, and even protocols, for monitoring cross-ecosystem responses to conservation initiatives are lacking. Here, we evaluate potential indicators, operating on different spatial, temporal, and biological scales, for measuring the effects of island-based restoration on coral reef ecosystems. We show that island restoration status had consistent effects on populations of tropical seabirds across spatial scales from 100 m to entire islands. Seabirds, in turn, provided nutrient subsidies that were incorporated by marine algae and coral-reef fishes, with the most pronounced effects closer to shore, at leeward sites, and at low trophic levels. Microbes and macroalgae exhibited assemblage-level responses to seabird-derived nutrients entering the marine environment, but there were few differences in coral reef benthic and fish assemblages. By identifying and focusing on specific indicators such as macroalgal nutrients, managers can better monitor cross-ecosystem responses to conservation interventions with limited resources
Placement des aides-soignants à la retraite pour invalidité : l'employeur public face aux dispositions relatives à la santé et à la sécurité au travail et aux dispositions relatives à l'âge limite d'exercice des fonctions
No full textInternational audienceNote sous CAA Toulouse, 4 juin 2024, no 22TL2121
Invasive macroalgae shape chemical and microbial waterscapes on coral reefs
No full textInternational audienceOver the past decades, human impacts have changed the structure of tropical benthic reef communities towards coral depletion and macroalgal proliferation. However, how these changes have modified chemical and microbial waterscapes is poorly known. Here, we assessed how the experimental removal of macroalgal assemblages influences the chemical and microbial composition of two reef boundary layers, the benthic and the momentum. Chemical and microbial waterscapes were spatially structured, both horizontally and vertically, according to macroalgal dominance and boundary layers. Microbes associated with reef degradation were enriched in the boundary layers surrounding macroalgal-dominated substrata. Dominant macroalgae were surrounded by a distinct chemical pool of diverse lipid classes (e.g., diterpenoids and glycerolipids) and labile organic matter (e.g., organooxygen compounds), which diffused from algal tissues to boundary layers according to their polarity. Finally, our results highlighted strong co-variations between specific algal-derived metabolites and planktonic microbes, giving insight into their roles in coral reef functioning and resilience
Enseigner la sociologie par la recherche participative (Polynésie française) ?
No full textInternational audienceThe teaching of sociology was introduced relatively recently in higher education in French Polynesia. It comes up against two challenges: a lack of relevant educational reference tools and incentives to contextualise knowledge as appropriate for overseas France. In the absence of basic general sociology work on this territory, sociology teachers in higher education must consider how to teach this discipline that is only just emerging across the region in a contextualised manner. To shed light on this issue, the article sets out an empirical and reflective approach to a sociology lesson taught in the territory, covering both the preparation and implementation of methods to introduce the sociology of French Polynesia in French Polynesia. On this basis, the article identifies the difficulties affecting the experimental teaching practices implemented with a view to transmitting a key sociology skill, i.e. the ability to distance oneself from everyday social realities in order to regard them as objects, in a context of substantial pedagogical freedom and a lack of reference tools for teachers.L’enseignement de la sociologie a été mis en place de manière relativement récente dans les formations du supérieur en Polynésie française. Il y fait face à un double défi : l’absence d’outils didactiques de référence pour l’enseignement de cette discipline et une incitation à contextualiser les savoirs en contexte ultramarin. En l’absence de travaux fondamentaux en sociologie générale sur ce territoire, une question d’ordre didactique se pose aux enseignants du supérieur dans cette discipline : comment enseigner de manière contextualisée une discipline encore émergeante au niveau territorial ? Afin d’apporter un éclairage sur cette question, l’article offre une approche empirique et réflexive d’un cours de sociologie enseigné sur ce territoire, en abordant à la fois la préparation et la mise en oeuvre de dispositifs d’initiation à la sociologie de la Polynésie française en Polynésie française. Sur cette base, l’article identifie les difficultés à l’oeuvre dans les pratiques expérimentales d’enseignement déployées en vue de transmettre une compétence « clé » en sociologie, c’est-à-dire la capacité de distanciation vis-à-vis des faits sociaux quotidiens afin de les appréhender comme des objets, dans un contexte marqué par une liberté pédagogique forte et l’absence d’outils didactiques de références
Les enjeux sociaux et sanitaires du vieillissement en Polynésie française
No full textInternational audienc
Mon Bagne
No full textInternational audienceAlphonse Humbert (1844-1922) fut un ardent républicain. Signataire de la célèbre « Affiche rouge » qui proclame « Place à la Commune ! » dès janvier 1871, il s'engage par la plume, au Père Duchêne. Après la Semaine sanglante, Humbert est arrêté, traduit en conseil de guerre et condamné aux travaux forcés à perpétuité.Voici son récit. Trop longtemps oublié, il n'était paru qu'en feuilleton dans la presse radicale entre 1880 et 1881. Humbert y décrit de sa plume alerte et précise ses premières années de bagne (1872-1875) : d'abord Toulon, puis le convoi de la Virginie, à destination de la Nouvelle-Calédonie. Là-bas, aux antipodes, une toute-puissante administration pénitentiaire préside aux destins des « scélérats » dont la France souhaite se débarrasser, tout en s'abritant derrière un projet de colonisation basé sur leur réhabilitation.La jeune colonie pénale et ses installations sont abondamment décrites dans ce texte, qui constitue une source de premier plan pour l'histoire de cet archipel. Plus et mieux que les autres forçats qui nous ont laissé leurs mémoires, Alphonse Humbert se place en observateur du bagne. En décrire la noirceur, la lourdeur administrative, les paradoxes et les absurdités, dépeindre les forçats dans leur complexité, leur monstruosité, leur honneur ou la richesse de leur langue, évoquer les rires et les joies aussi - même fugaces -, sont autant de facettes d'un récit remarquable qui, trente ans avant celui d'Albert Londres, dresse un réquisitoire implacable contre l'effroyable châtiment de l'exil
Qui savait quoi ? Circulations et déperditions de savoirs en matière de radioprotection
No full textInternational audienceCette communication explore le processus d’élaboration des normes de radioprotection avant le premier essai réalisé au Centre d’expérimentation du Pacifique (CEP) en 1966. Les armées françaises ont pu s’appuyer sur des expertises transnationales, franco-étasuniennes notamment, mais aussi européennes du fait des normes produites par les communautés européennes des années 1960, et proprement internationales avec la Commission internationale de protection radiologique (CIPR) et l’Agence internationale de l’énergie atomique (AIEA). Le dispositif de sûreté, élaboré en Polynésie française par les Armées et le Commissariat à l’énergie atomique (CEA), dont les experts sont réunis dans des services mixtes de sécurité, tient compte de l’état des connaissances, mais aussi des discours rassurants qui ont été tenus par leurs experts et les politiques devant les populations locales, dans un contexte de dénonciation internationale des effets induits par les essais nucléaires. En minorant les dangers devant le public polynésien et international, et en exagérant la maîtrise du risque radiologique, les responsables de ce dispositif se sont piégés jusqu’à ne pas déployer toutes les mesures préventives ou curatives qui auraient contredit cette rhétorique communicationnelle, qu’il s’agisse d’abris contre les retombées ou d’évacuations des îles les plus concernées