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Feeding ecology of the Indian yellow-nosed albatross Thalassarche carteri at the subtropical Amsterdam Island
No full textInternational audienceZone (STZ) during the non-breeding period (Cherel et al. 2013). A few species breed both north and south of the Subtropical Front (STF); they include the sooty albatross Phoebetria fusca in the Atlantic and Indian Oceans, the Buller's albatross Thalassarche bulleri in New Zealand waters, the Atlantic yellow-nosed albatross T. chlororhynchos (AYNA) in the Atlantic Ocean, and the Indian yellow-nosed albatross T. carteri (IYNA) in the Indian Ocean. The two yellow-nosed albatrosses are phylogenetically closely-related taxa that are considered as valid species, based on genetic variation, consistent plumage and behavioural differences, and non-overlapping breeding ranges (Robertson and Nunn 1998; Flood 2015; Abeyrama et al. 2021). Both species are listed as Endangered in the IUCN Red List (IUCN 2024) due to the limited number of breeding sites, threats from introduced predators and diseases, and impact of commercial fishing (Abeyrama et al. 2021).</div
Sibling similarity in telomere length in Adélie penguin chicks
No full textInternational audienceEarly life telomere length is thought to influence and predict an individual's fitness. It has been shown to vary significantly in early life compared to adulthood. Investigating the factors influencing telomere length in young individuals is therefore of particular interest, especially as the relative importance of heredity compared to postnatal conditions remains largely uncertain. Adélie penguins are eco-indicators of the Antarctic ecosystem and their population are currently undergoing variable trajectories due to climate change. Here, we conducted a correlative study to investigate how telomere length was influenced by external and internal factors in Adélie penguin chicks. We found that most of the parameters we tested, including sex, body mass, brood size and hatching order as well as parental foraging trip duration, did not significantly influence chick telomere length at 32 days. However, siblings had similar telomere length, suggesting that hereditary factors play a stronger role in determining telomere length at this stage compared to the post-natal environment. In addition, telomere length and oxidative damage did not directly correlate but did interact in a complex way mediated by chick mass. High levels of oxidative damage were associated with longer telomeres in heavy chicks, whereas they were associated with shorter telomeres in light chicks. Although this mass-dependent relationship between telomere length and oxidative damage needs to be confirmed in future studies, it could reflect two different scenarios: (1) short telomeres may mimic the cost of poor nutritional conditions and oxidative damage in light chicks; (2) long telomeres may be maintained despite high oxidative damage in heavy chicks thanks to optimal nutritional conditions
Gas radiation effect on a turbulent thermal plume in a confined cavity using direct numerical simulation
No full textInternational audienceInfluence of gas radiation on a thermal plume is investigated in a cubical cavity filled with humid air (air/H2O mixture) by means of Direct Numerical Simulation. In this work, radiation within the fluid is considered by the SLW model developed by Denison and Webb and numerically solved using the Discrete Ordinate Method (S8 quadrature). The simulations are conducted for humid air with different amounts of water vapor and compared to the case without radiation. Two values of the Rayleigh numbers, 2 X 106 and 1 X 109, are considered, corresponding to steady and turbulent flow regimes. Steady solutions show that gas radiation tends to reduce the spatial spreading of the thermal plume and to homogenize the temperature field away from the heat source. Gas radiation also results in an attenuation of the global circulation. It is shown that the radiative fluxes are much higher than convective fluxes on the isothermal walls, and the radiative heat transfer still increases with the water vapor concentration. For the turbulent regime, accounting for radiation leads to a less fluctuating behavior of the plume and induces a global shift of the mean temperature field in most of the cavity, except in the region around the heat source. Regarding the mean flow field, thermal radiation tends to weaken the intensity of flow circulation, but to accelerate the flow velocity along the centerline above the heat source
The Use of Simulation/Games in Territories: Key Factors to Favor Effects on Territorial Development
No full textInternational audienceThis chapter explores the impact of simulation/games on decision making processes, focusing on how they influence social constructs, perceptions, and stakeholder relationships rather than direct decision outcomes. By analyzing multiple case studies, the chapter identifies the factors that link in-game experiences to real-world contexts, such as the degree of alignment between the simulation and reality, role asymmetries, and the flexibility of the game (free-play). It highlights how these elements create a dynamic tension by simultaneously mirroring real world situations (similarities) and introducing shifts or deviations from reality (dissonances), thereby fostering reflective attitudes and transformative effects. Additionally, the chapter emphasizes the importance of the deployment context and participant selection in shaping the outcomes of simulation/games. It concludes by advocating for the integration of local contexts in the co-construction of simulations and calls for broader interdisciplinary research to rethink how we approach the question of their effects in the context of their application with stakeholders of socio-ecological systems. The findings suggest that simulation/games, when aligned with local dynamics and involving the right stakeholders, can significantly enhance collective understanding and action in environmental planning
Plan de gestion de données du projet "Evolution de l'identité PAtrimoniale des Marais des Pertuis charentais en réponse à l'Aléa de Submersion marine (PAMPAS)"
No full textPAMPAS : Evolution de l’identité PAtrimoniale des Marais des Pertuis charentais en réponse à l’Aléa de Submersion marine est un projet de recherche collaborative (PRC) de l’Agence Nationale de la Recherche (identifiant ANR-18-CE32-0006).PAMPAS est un projet interdisciplinaire visant à répondre à la fois aux enjeux sociétaux actuels d’adaptation au changement climatique et de transmission du patrimoine présent dans les zones de marais littoraux, appliqué à une échelle locale, mais transposable à l’échelle plus large des zones humides littorales.Il aborde la question du fonctionnement et du devenir des zones humides côtières face à l’aléa submersion marine à travers le prisme de l’identité patrimoniale pour aller au-delà des approches classiques d’évaluation de l’écologie de la conservation, de l’économie et de la gestion du patrimoine culturel, pour une meilleure gestion de ce patrimoine
Organic and metallic contaminants in reef fish from the South Pacific region, with emphasis on New Caledonia
No full textOrganic and metallic contaminants in reef fish from the South Pacific region, with emphasis on New CaledoniaApproximately 1000 coral reef fish were collected from 27 sites across 8 island countries and territories in the Pacific: Fiji, French Polynesia, Kiribati, New Caledonia, Samoa, Vanuatu, Wallis and Futuna, and Rapa Nui. Around 400 of the fish were obtained in New Caledonia, making it the most extensively sampled. Fish were analysed for their concentrations of 36 pesticides and metallic trace elements. Through measuring contaminant concentrations at the individual fish level and integrating these results at the fish community level, our study identifies potential factors explaining their prevalence in fish communities at the New Caledonian and South Pacific regional scales. Spatial patterns varied significantly, depending on the compound, with concentrations in fish flesh generally higher in the central and southwest Pacific than in the eastern part of the Pacific basin. These patterns were influenced by biological, environmental, anthropogenic and biogeographical factors such as fish size, sea surface temperature, gross domestic product per capita, and land area. In New Caledonia, fish size also emerged as the most important correlate of contaminant concentrations. Monthly rainfall was the second most important variable for pesticides, whereas the reef surface area was the second variable explaining metallic element concentrations. Our results enhance our understanding of the extent of contamination in the South Pacific, while underscoring the urgent need for long-term and large-scale spatial monitoring of diverse contaminants in this region
Wave Friction Factor and Roughness Definition in Multi‐Scale Coral Barrier Reef
No full textInternational audienceWave frictional dissipation is a key process in rough seabed’s environments such as coral reefs, expected to significantly reduce incoming wave energy. In phase‐averaged models, wave dissipation is typically estimated through a wave friction factor which is dependent of the near‐bed orbital excursion and the hydraulic length, a proxy for the seabed substrate roughness. A field experiment was conducted in the South‐Western coral reef barrier of Mayotte (Indian Ocean) to compute through a frequency‐integrated wave energy balance. Significant time and space variations of have been observed, driven by the evolution of the wavefield and the diversity of coral geometry and scales found along the barrier. The fine reef architecture has been examined thanks to a high‐resolution multi‐beam echo sounder survey. This study has reassessed the established link between hydraulic roughness length and roughness standard deviation; it also indicates that second‐order roughness metrics may also significantly explain variations in . Future challenges remain in the proper definition of the length scales of seabed variability attributed to roughness and to bathymetry
Dual effect of bacteria on corrosion mechanisms of stainless steel and carbon steel
No full textInternational audienceCorrosion mechanisms are complex, resulting from multiple factors such as the environment and the intrinsic properties of the material, which are difficult to dissociate. The development of certain aggressive bacteria, which strongly impact corrosion mechanisms, seems to be linked to the prior formation of biofilms on the surface of the studied material, modifying the properties of the surface electrolyte and thus influencing the kinetics and mechanisms of corrosion. Recent results show that the same marine bacterial strain, Roseovarius sp., known for forming thick biofilms in marine environments, can have different effects linked to the respective corrosion mechanisms of the materials studied. The biofilms seem to provide significant protection for steels sensitive to general corrosion, where the limiting factor is the cathodic reaction of oxygen reduction. In contrast, stainless steels, which normally exhibit good electrochemical properties, show a degradation of those properties in presence of biofilms. These steels are subject to localized corrosion, and the limiting factor is often the low reactivity of their dense, chromium-enriched oxide layer. Our preliminary results from electrochemical impedance spectroscopy (EIS) suggest a shift of the behavior to a significant increase in pitting susceptibility. After a certain period of biofilms development, the charge transfer resistance becomes similar to that measured on carbon steel after the same exposure time. Despite the differences in corrosion mechanisms, it appears that the presence of biofilms on both types of steel leads them to the same limiting factor. Moreover, the in-situ detection of bacterial corrosion signatures presents a major challenge for the industry, as it could allow to anticipate and prevent damage. Changes in the local composition of the electrolyte on the steel surface (interface), caused by biofilms development, can alter the electrochemical double layer, which has been detected using EIS