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Floriane Provost, Dimitri Zigone, Emmanuel Le Meur, Jean-Philippe Malet, Clément Hibert. (2023). Surface dynamics and history of the calving cycle of the Astrolabe glacier (Antarctica) derived from optical imagery.
Abstract: The recent calving of the Astrolabe glacier (Terre Adélie, East Antarctica) in November 2021 presents an opportunity to better understand the processes leading to ice fracturing. Optical satellite imagery is used to retrieve the calving cycle of the glacier since 2000 by mapping the ice front location. A recent archive of high resolution optical images from Sentinel-2 is used to measure the ice motion and the ice strain rates for the period 2017–2021 in order to document fractures and rift evolution. These observations are compared with sea ice extent and concentration measurements. We found that a significant change in the sea ice melting periodicity at the vicinity of the Astrolabe glacier occurred in the last decade (2011–2021) with respect to previous observations (1979–2011). After 2011, the occurrence of consecutive years of high sea-ice concentration at the vicinity of the glacier seems to have favored the ice tongue spatial extension. This lead to an unprecedentedly observed extension of the ice tongue until November 2021. The analysis of strain rate time series revealed that the glacier dislocated suddenly in June 2021 in the middle of the winter before releasing an iceberg of around 20 km2 in November 2021 at the onset of sea ice melting season. These observations suggest that although the presence of sea ice favors glacier extension, its buttressing effect may not be sufficient to prevent fracture opening.
Programme: 411
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Forget F., Bretel P., Genthon C., Berne A., Dufresne J.L., Lemonnier F., Madeleine J.B, Roussel M.R., Sultan E., Veron D., Vignon E., Wiener V. (2023). Quinze ans d’observations climatiques à Dome C et en Terre Adélie avec le programme CALVA : données, découvertes, et évolution.
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Genthon, C., le Consortium AWACA. (2023). Le projet AWACA.
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Guilhermic C., Mouret A., Howa H., Pusceddu A., Baltzer A., Nardelli M.P. (2023). Effect of environmental gradients generated by tidewater glacier melting on sedimentary habitats and benthic meiofauna in Kongsfjorden (Svalbard): seasonal observations.
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Guillaume Delpech, James M. Scott, Michel Grégoire, Bertrand N. Moine, Dongxu Li, Jingao Liu, D. Graham Pearson, Quinten H. A. van der Meer, Tod E. Waight, Gilbert Michon, Damien Guillaume, Suzanne Y. O'Reilly, Jean-Yves Cottin, André Giret. (2023). The subantarctic lithospheric mantle (Vol. 56).
Abstract: We present a summary of peridotite in the Subantarctic (46–60° S) surrounding the Antarctic Plate. Peridotite xenoliths occur on the Kerguelen Islands and Auckland Islands. The Kerguelen Islands are underlain by a plume, whereas the Auckland Islands are part of continental Zealandia, which is a Gondwana-rifted fragment. Small amounts of serpentinized peridotite has been dredged from fracture zones on the Southeast Indian Ridge, Southwest Indian Ridge and Pacific Antarctic Ridge, and represent upwelled asthenosphere accreted to form lithosphere. Suprasubduction-zone peridotite was collected from two locations on the Sandwich Plate. Peridotites from most subantarctic occurrences are moderately to highly depleted, and many show signs of subsequent metasomatic enrichment. Os isotopes indicate that subantarctic continental and oceanic lithospheric mantle contains ancient fragments that underwent depletion long before formation of the overlying crust.
Programme: 1077
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Guillaume Hubert, Philippe Ricaud, Vincent Favier, Jonathan Wille. (2023). Impact of the atmospheric river occurring in March 2022 on east Antarctica on Cosmic-Rays measurements.
Abstract: The primary cosmic rays (CRs) interact with atmospheric atoms, producing secondary CRs (neutron, proton, muon etc.). Meteorological conditions influence the secondary CRs properties, such as the atmospheric pressure and the hydrometric properties (snowfall, the atmospheric water vapor and liquid water, the soil moisture). The CHINSTRAP project aims at recording CR induced-neutron spectra at Concordia Antarctic station, over a wide energy range from meV up to tens of GeV with a short time resolution. At the same time, a radiometer records continuously the water vapor contents and temperatures profiles (HAMSTRAD project). In March 2022, an atmospheric river (AR) caused some of the highest temperature anomalies ever observed over Antarctica (absolute temperature record of -9.4 °C on March 18th at Concordia). The ARs transport large amounts of moisture from the mid- to high-latitudes, modifying considerably usual dry conditions observed at Concordia. This AR event attenuated CRs measurements at Concordia, something previously never observed. A first analysis shows a correlation between the CR induced neutron flux decreases (in the order of 15%) and the increases of the integrated water vapor and liquid water path (IWV and LWP, respectively). This work demonstrates the importance of CRs attenuation during particle transport mechanisms in a highly saturated atmosphere.
Programme: 1112
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Guillaume Schwob, Léa Cabrol, Thomas Saucède, Karin Gérard, Elie Poulin, Julieta Orlando. (2023). Unveiling the co-phylogeny signal between plunderfish Harpagifer spp. and their gut microbiomes across the Southern Ocean.
Abstract: Understanding the factors that sculpt fish gut microbiome is challenging, especially in natural populations characterized by high environmental and host genomic complexity. Yet, closely related hosts are valuable models for deciphering the contribution of host evolutionary history to microbiome assembly, through the underscoring of phylosymbiosis and co-phylogeny patterns. Here, we hypothesized that the recent allopatric speciation of Harpagifer across the Southern Ocean (1.2–0.8 Myr) will promote the detection of robust phylogenetic congruence between the host and its microbiome. We characterized the gut mucosa microbiome of 77 individuals from four field-collected species of the plunderfish Harpagifer (Teleostei, Notothenioidei), distributed across three biogeographic regions of the Southern Ocean. We found that seawater physicochemical properties, host phylogeny and geography collectively explained 35% of the variation in bacterial community composition in Harpagifer gut mucosa. The core microbiome of Harpagifer spp. gut mucosa was characterized by a low diversity, mostly driven by selective processes, and dominated by a single Aliivibrio taxon detected in more than 80% of the individuals. Almost half of the core microbiome taxa, including Aliivibrio, harbored co-phylogeny signal at microdiversity resolution with Harpagifer phylogeny. This suggests an intimate symbiotic relationship and a shared evolutionary history with Harpagifer. The robust phylosymbiosis signal emphasizes the relevance of the Harpagifer model to understanding the contribution of fish evolutionary history to the gut microbiome assembly. We propose that the recent allopatric speciation of Harpagifer across the Southern Ocean may have generated the diversification of Aliivibrio into patterns recapitulating the host phylogeny. Importance Although challenging to detect in wild populations, phylogenetic congruence between marine fish and its microbiome is critical, as it allows highlighting potential intimate associations between the hosts and ecologically relevant microbial symbionts.Through a natural system consisting of closely related fish species of the Southern Ocean, our study provides foundational information about the contribution of host evolutionary trajectory on gut microbiome assembly, that represents an important yet underappreciated driver of the global marine fish holobiont. Notably, we unveiled striking evidence of co-diversification between Harpagifer and its microbiome, demonstrating both phylosymbiosis of gut bacterial communities, and co-phylogeny of specific bacterial symbionts, in patterns that mirror the host diversification. Considering the increasing threats that fish species are facing in the Southern Ocean, understanding how the host evolutionary history could drive its microbial symbiont diversification represents a major challenge to better predict the consequences of environmental disturbances on microbiome and host fitness.
Programme: 1044
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Hassen Allegue, Denis Réale, Baptiste Picard, Christophe Guinet. (2023). Track and dive-based movement metrics do not predict the number of prey encountered by a marine predator (Vol. 11). Bachelor's thesis, , .
Abstract: Studying animal movement in the context of the optimal foraging theory has led to the development of simple movement metrics for inferring feeding activity. Yet, the predictive capacity of these metrics in natural environments has been given little attention, raising serious questions of the validity of these metrics. The aim of this study is to test whether simple continuous movement metrics predict feeding intensity in a marine predator, the southern elephant seal (SES; Mirounga leonine), and investigate potential factors influencing the predictive capacity of these metrics.
Keywords: Accelerometry Area-restricted search Diving behavior Foraging behavior Marine predator Prey encounter events
Programme: 109,1201
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Hennion Françoise, Binet Françoise. (2023). Adaptation des plantes subantarctiques au changement climatique et dynamique et trajectoires sol-plante.
Abstract: Les îles subantarctiques de Kerguelen sont soumises à un changement climatique rapide et intense. Ces îles abritent des espèces végétales endémiques de grand intérêt dans l’hémisphère sud. La flore comporte peu d’espèces et leurs interactions sont mal connues. De tels systèmes pourraient être particulièrement fragiles, et a contrario leur résilience dépendre plus fortement des interactions biotiques entre espèces. Le projet PlantADAPT vise à évaluer et suivre la réponse des espèces de plantes endémiques des îles Kerguelen au changement climatique, en prenant en compte le système plante-sol intégré et les interactions biotiques (plante holobionte). Dans l’objectif d’évaluer les parts respectives de la plasticité phénotypique et de l’adaptation locale dans la variation phénotypique, l’expérience en Jardins Communs est un dispositif déterminant. Nous développons aussi des approches d’écologie fonctionnelle des communautés microbiennes et du système sol associé.
Programme: 1116
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Henri Weimerskirch, Alexandre Corbeau, Adrien Pajot, Samantha C. Patrick, Julien Collet. (2023). Albatrosses develop attraction to fishing vessels during immaturity but avoid them at old age (Vol. 290).
Abstract: Animals have to develop novel behaviours to adapt to anthropogenic activities or environmental changes. Fishing vessels constitute a recent feature that attracts albatrosses in large numbers. While they provide a valuable food source through offal and bait, they cause mortalities through bycatch, such that selection on vessel attraction will depend on the cost–benefit balance. We examine whether attraction to fishing and other vessels changes through the lifetime of great albatrosses, and show that attraction differed between age classes, sexes and personality. Juveniles encountered fewer vessels than adults, but also showed a lower attraction to vessels when encountered. Attraction rates, especially for fishing vessels, increased through immaturity to peak during adulthood, decreasing with old age. Shy females had lower attraction to vessels and shy males remained at vessels longer, suggesting that bolder individuals may outcompete shyer ones, with positive consequences for mass gain. These results suggest that attraction to vessels is a learned process, leading to an increase with age, and is not the result of preferential attraction to new objects by juveniles. Overall, our findings have important conservation implications as a result of potential strong differential selection on the risk of bycatch for age classes, personality types, populations and species.
Keywords: albatross attraction conservation learning process personality vessels
Programme: 109
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