HAL Portal UPF (Université de la Polynésie française)
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Light intensity modulates the effect of thermal stress on giant clams and their symbiotic zooxanthellae
No full textInternational audienceGradual climate change and extreme marine heatwaves (MHWs) pose a serious threat to tropical marine ecosystems, endangering the fisheries and aquaculture resources they support. A better understanding of species physiological responses to climate change-related stressors can help anticipate the risks and develop adaptive management strategies. While temperature is the main driver pushing organisms away from their optimal physiological and ecological performance, thermal stress is modulated by additional stressors in the wild, which cumulatively determine the extent of the impacts observed in nature. In this study we explored individual-level mechanisms driving the sensitivity of a symbiotic organism—the giant clam Tridacna maxima—to a range of temperatures (24, 27, 29, and 31 °C) and light intensities (150 and 1000 µmol m−2 s−1). After 18 days of exposure, we characterized the physiological response of both the symbiotic microalgae and the animal host using PAM fluorometry, respirometry, weight measurements, chlorophyll-a quantification, and measurements of zooxanthellae density and size. Our data revealed the crucial role of light in modulating the sensitivity of giant clams to warming. The effect of light and its interaction with temperature were stronger than temperature alone in driving responses of both the zooxanthellae (photosynthetic performance, zooxanthellae density and size, and oxygen production) and the host (respiration rate and condition index). By explicitly considering the interplay between temperature and light in photo-autotrophic organisms, aquaculture and fishery managers might have a tool for minimizing the impacts of climate change and MHW events on their activities
Safety in the shallows: nearshore coastal habitats can provide physical and thermal features that optimize escape performance in newborn blacktip reef sharks ( Carcharhinus melanopterus )
No full textInternational audienceThe prevailing shark nursery paradigm suggests that high survival in these habitats is primarily driven by reduced predator encounters: so-called pre-encounter risk. In this study, we propose an alternative or complementary mechanism: that some nurseries may lower post-encounter risk by providing environmental conditions that maximize escape performance. To test this hypothesis, we examined how temperature, depth and habitat complexity influence the escape performance of newborn blacktip reef sharks (Carcharhinus melanopterus) in Mo′orea, French Polynesia. In a controlled setting, we exposed 48 newborn sharks to four temperature treatments (25, 27, 29 and 31°C) and measured fast-start acceleration, turning rate and latency to respond to a stimulus. We also calculated aerobic scope at 27, 29 and 31°C, as greater aerobic scope is associated with faster recovery from burst swimming. Our results show that warmer temperatures improve escape performance, with 29% higher acceleration, 9% faster turning rates and 48% shorter reaction times at elevated temperatures. Furthermore, aerobic scope remained ≥80% of its maximum capacity between 27.5 and 30.8°C, suggesting that newborn sharks can sustain high metabolic performance within this thermal window. Field measurements at nursery habitats revealed that daily thermal fluctuations generally remained within this optimal aerobic scope range, meaning that newborns can maintain high escape performance for most of the day. Additionally, high-resolution mapping confirmed that previously reported home ranges were associated with shallow (median depth = 0.74 m), structurally complex reef flats dominated by coral substrate. The combination of reduced hydrodynamic drag in shallow water and increased manoeuvrability in complex habitats likely enhances predator evasion. However, extreme warming events that exceed critical thermal limits may trigger behavioural trade-offs that compromise escape performance and elevate predation risk. Our findings suggest that these nurseries provide habitat-specific advantages for predator evasion, reinforcing their critical role in the survival of newborn sharks
La violence physique à l'encontre d'un agent public qui a répondu à une invective n'est pas constitutive d'un accident de service
No full textInternational audienceNote sous CAA Toulouse, 18 février 2025, no 23TL0121
Growth Patterns of Reef-Building Porites Species in the Remote Clipperton Atoll Reef
No full textInternational audienceRemote reefs offer insights into natural coral dynamics, influenced by regional environmental factors and climate change fluctuations. Clipperton Atoll is the eastern tropical Pacific’s most isolated reef, where coral reef growth and life strategies have been poorly studied so far. Recognizing the coral species’ growth response might help understand ecological dynamics and the impacts of anthropogenic stressors on coastal reefs. The present study evaluates annual coral growth parameters of the most abundant coral reef-building species, Porites australiensis, Porites arnaudi, Porites lutea, and Porites lobata. The results showed that during 2015–2019, corals exhibited the lowest annual linear extension (0.65 ± 0.29 cm yr−1), skeletal density (1.14 ± 0.32 g cm−3), and calcification rates (0.78 ± 0.44 g cm−2 yr−1) for the genera along the Pacific. Differences in growth patterns among species were observed, with Porites lutea and Porites lobata showing a higher radial extension, developing massive-hemispherical morphologies, and acting as structural stabilizers; meanwhile, P. arnaudi and P. australiensis exhibited more skeletal compaction but also with a high plasticity on their morphologies, contributing to benthic heterogeneity. These differences are particularly important as each species fulfills different ecological functions within the reef, contributing to the ecosystem balance and enhancing the relevance of the massive species in the physical structure of remote reef systems, such as Clipperton Atoll
Pas de recours abusif aux CDD pour un agent exerçant pendant plus de vingt-cinq ans en tant que vacataire
No full textInternational audienceNote sous CAA Lyon, 19 février 2025, no 23LY0180
Exploring potential fish sound producers in Polynesian lower mesophotic coral reefs
No full textInternational audienceMesophotic coral reefs host unique fish assemblages and highly diverse biological sounds. However, many of the sources of these sounds remain unknown. The objectives of this study are to identify, based on the literature, the soniferous fish species present in the deep part of mesophotic coral ecosystems (MCEs) in French Polynesia; and to infer the sounds produced by the species present to link them with previously recorded sounds. A total of 39 fish families through to produce sounds were found to be possibly present at 120 m depth. This list includes well-known families such as Serranidae and Ophidiidae. The most abundant sound recorded in Polynesian mesophotic reefs exhibits similarities to sounds produced by Mediterranean Scorpaena species (Scorpaenidae), a genus also present in Polynesian MCEs. This study provides initial insights into which soniferous fish taxa are present in Polynesian MCE
L’écologie des violences familiales en Polynésie française: action située, effets de structure et changement social
No full textInternational audiencela violence comme champ d'expériences : Témoignages de détenus dans les prisons de Tahiti aujourd'hui</div
Haro sur les marges : plus c’est gros, plus ça passe !
No full textArticle de vulgarisation scientifiqueEn exhumant un avis de 2019 de l’APC sur les mécanismes d’importation et de distribution que l’on croyait (ou que l’on espérait) oublié, les « experts » d’ISLE ont, lors du colloque sur la vie chère, déclenché une forme d’irrationalité autour des marges pratiquées dans le Pays. Jusqu’à croiser parfois dans le débat des chiffres fantasques.Article disponible sur le lien :https://www.pacific-pirates-media.com/haro-sur-les-marges-plus-cest-gros-plus-ca-passe
Peut-on réellement lutter contre la « vie chère » en détruisant l’économie de marché ?
No full textArticle de vulgarisation scientifiqueOn January 23, 2025, the French National Assembly adopted at first reading a bill aimed at tackling the cost of living in the overseas territories. While the text does not directly concern French Polynesia—since it has authority over its own economic matters—it is well known that local policymakers tend to draw inspiration from measures applied in other overseas territories or in mainland France. For the sake of the common good of Polynesians, let us hope that this will not be the case this time.The full article is available in French at the following link:https://www.pacific-pirates-media.com/peut-on-reellement-lutter-contre-la-vie-chere-en-detruisant-leconomie-de-marche/Le 23 janvier 2025, l’Assemblée nationale a adopté en première lecture une proposition de loi destinée à lutter contre le coût de la vie en outre-mer. Un texte qui ne concerne pas directement la Polynésie française, compétente en matière économique, mais on connaît la propension locale à s’inspirer des mesures en vigueur dans les autres outre-mer ou en métropole. Espérons dans l’intérêt commun des Polynésiens qu’il n’en sera pas ainsi cette fois.L'article intégral est disponible en français sur le lien suivant :https://www.pacific-pirates-media.com/peut-on-reellement-lutter-contre-la-vie-chere-en-detruisant-leconomie-de-marche