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Benjamin Wasilewski, Luc S. Doucet, Bertrand Moine, Hugues Beunon, Guillaume Delpech, Nadine Mattielli, Vinciane Debaille, Adélie Delacour, Michel Grégoire, Damien Guillaume, Jean-Yves Cottin. (2017). Ultra-refractory mantle within oceanic plateau: Petrology of the spinel harzburgites from Lac Michèle, Kerguelen Archipelago (Vol. 272-273).
Abstract: The study presents major and trace element compositions of whole-rocks and minerals of 24 spinel harzburgite xenoliths from the Lac Michèle locality in the northern part of the Kerguelen Archipelago (South Indian Ocean). The samples are modally homogeneous and large enough to provide representative whole-rock samples. Their Mg# are high (0.91 to 0.93) and they have 16–29wt.% orthopyroxene (opx) and low clinopyroxene contents (0.1–2.8wt.%). They display a wide range of serpentinisation, which result in LOI contents ranging from 0 to 3.5wt.%. The spinel-bearing harzburgites from Lac Michèle are the most refractory peridotites identified so far among peridotite xenoliths available on the Kerguelen Archipelago and within the oceanic lithosphere. By contrast with most of the peridotite xenoliths from Kerguelen, they have been more preserved from post-formation processes such as metasomatic processes. The major and trace element compositions of the least serpentinised spinel harzburgites indicate an origin by ~30% of polybaric decompression fractional melting between 5GPa and ≤1GPa. Thus, the spinel harzburgites from Lac Michèle, situated at the top of the Kerguelen lithospheric mantle, are residues of melting that took place over a broad range of depth and mostly in the garnet stability field. Our results, in comparison with published data on mantle xenoliths worldwide, show that spinel harzburgites from Lac Michèle have major and modal compositions that fall in the range of cratonic peridotites rather than abyssal peridotites, oceanic island peridotites, subduction zones peridotites and off-cratonic peridotites. This indicates (i) they formed in similar condition as for the ancient continental lithospheric mantle or (ii) they are fragment of ancient continental lithospheric mantle incorporated in the Kerguelen plateau.
Keywords: Kerguelen Oceanic plateau Spinel harzburgites Ultra-refractory Xenoliths
Programme: 1077
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Xu, G.; Frey, F.A.; Weis, D.; Scoates, J.S.; Giret, A. (2007). Flood basalts from Mt. Capitole in the central Kerguelen Archipelago: Insights into the growth of the archipelago and source components contributing to plume-related volcanism. Geochem. Geophys. Geosyst., 8.
Abstract: The Kerguelen Archipelago, constructed on the submarine Northern Kerguelen Plateau, is attributed to Cenozoic volcanism arising from the Kerguelen hot spot. Geochemical studies of 325 to 1000 m thick lava sections of the ?30 to 25 Ma flood basalt forming the bulk of the archipelago show a temporal change from older tholeiitic basalt to younger slightly alkalic basalt. This compositional transition is expressed in a 630 m lava section at Mt. Capitole where the lava sequence is lowermost tholeiitic basalt overlain by slightly alkalic basalt overlain by plagioclase-rich cumulates that are mixtures of plagioclase-phyric basalt and more evolved magmas. During growth of the archipelago, magma supply from the hot spot was variable and at times sufficiently low to enable extensive crystal fractionation; e.g., at Mt. Capitole and nearby Mt. Tourmente only 10 of 120 lava flows have >6 wt% MgO. On the basis of this study and previous isotopic data for the ?34 Ma submarine lavas erupted on the Northern Kerguelen Plateau, other flood basalt sections in the Kerguelen Archipelago, and younger lavas erupted in the archipelago and at Heard Island, there is significant Sr, Nd, Hf, and Pb isotopic heterogeneity that can be explained by two stages of mixing. The first mixing event, best shown by the submarine lavas, is between components that are related to Indian Ocean mid-ocean ridge basalt (MORB) and the Kerguelen hot spot. From ?34 Ma to <1 Ma, on average the proportion of the MORB-related component decreased. Subsequently, a second mixing process involved addition of a component with relatively high 87Sr/86Sr (>0.7060) and low 143Nd/144Nd (<0.5125) and 176Hf/177Hf (<0.2827) and nonradiogenic Pb isotope ratios (<17.9 for 206Pb/204Pb). We infer that this component was lower continental crust.
Keywords: Kerguelen mantle plume; Kerguelen Archipelago; Mt. Capitole; lower continental crust; Sr; Nd; Hf; Pb isotopic ratios; 1037 Geochemistry: Magma genesis and partial melting; 1038 Geochemistry: Mantle processes; 1065 Geochemistry: Major and trace element geochemistry
Programme: 444
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Gregory B. Cunningham, Richard W. Van Buskirk, Mark J. Hodges, Gabrielle A. Nevitt. (2012). Responses of common diving petrel chicks (Pelecanoides urinatrix) to burrow and colony specific odours in a simple wind tunnel (Vol. 24).
Abstract: Researchers have previously assumed that common diving petrels (Pelecanoides urinatrix) have a limited sense of smell since they have relatively small olfactory bulbs. A recent study, however, showed that adult diving petrels prefer the scent of their own burrow compared to burrows of other diving petrels, implying that personal scents contribute to the burrow's odour signature. Because diving petrels appear to be adapted to use olfaction in social contexts, they could be a useful model for investigating how chemically mediated social recognition develops in birds. A first step is to determine whether diving petrel chicks can detect familiar and unfamiliar odours. We compared behavioural responses of chicks to three natural stimuli in a wind tunnel: soil collected from their burrow or colony, and a blank control. During portions of the experiment, chicks turned the least and walked the shortest distances in response to odours from the nest, which is consistent with their sedentary behaviour within the burrow. By contrast, behaviours linked to olfactory search increased when chicks were exposed to blank controls. These results suggest that common diving petrel chicks can detect natural olfactory stimuli before fledging, and lay the foundation for future studies on the role of olfaction in social contexts for this species.
Keywords: Kerguelen kin recognition olfaction procellariiform
Programme: 109
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A. Jaffal, N. Givaudan, S. Betoulle, A. Terreau, S. Paris-Palacios, S. Biagianti-Risbourg, E. Beall, H. Roche. (2011). Polychlorinated biphenyls in freshwater salmonids from the Kerguelen Islands in the Southern Ocean (Vol. 159).
Abstract: The Subantarctic Kerguelen Islands (49°S, 70°E) contain freshwater ecosystems among the most isolated in the world. Concentrations of polychlorinated biphenyls (PCBs) were assessed in the muscle of 48 brook trout and 38 brown trout caught during summer and spring 2006 in the rivers, lakes and ponds of Kerguelen. The sum of 29 PCBs averaged 404 and 358ngg−1 lipid, and dioxin-like PCB was 19 and 69ngg−1 lipid, in brook and brown trout, respectively. The values showed a high variability and some fish accumulated PCBs at levels similar to those of fish from impacted areas. While inter-sex differences were limited, the season and the morphotype appeared to have the most influence. Fish captured in summer had muscle PCB concentrations about three times higher than those caught in spring and the ‘river’ morphotype of brook trout showed the highest PCB levels.
Keywords: Kerguelen Islands PCB accumulation Salmonids Sub-Antarctic area
Programme: 409
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Colinet Hervé, Sinclair Brent J, Vernon Philippe, Renault David, . (2015). Insects in fluctuating thermal environments.
. Annu. Rev. Entomol., 60, 123–40.
Abstract: All climate change scenarios predict an increase in both global temperature means and the magnitude of seasonal and diel temperature variation. The nonlinear relationship between temperature and biological processes means that fluctuating temperatures lead to physiological, life history, and ecological consequences for ectothermic insects that diverge from those predicted from constant temperatures. Fluctuating temperatures that remain within permissive temperature ranges generally improve performance. By contrast, those which extend to stressful temperatures may have either positive impacts, allowing repair of damage accrued during exposure to thermal extremes, or negative impacts from cumulative damage during successive exposures. We discuss the mechanisms underlying these differing effects. Fluctuating temperatures could be used to enhance or weaken insects in applied rearing programs, and any prediction of insect performance in the field-including models of climate change or population performance-must account for the effect of fluctuating temperatures.
Keywords: Jensen's inequality, climate change, life history traits, temperature variations, thermal tolerance,
Programme: 136
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Tabouret Hélène, Pomerleau Sébastien, Jolivet Aurélie, Pécheyran Christophe, Riso Ricardo, Thébault Julien, Chauvaud Laurent, Amouroux David, . (2012). Specific pathways for the incorporation of dissolved barium and molybdenum into the bivalve shell: An isotopic tracer approach in the juvenile Great Scallop (Pecten maximus)
. Mar. Environ. Res., 78, 15–25.
Abstract: Dissolved barium and molybdenum incorporation in the calcite shell was investigated in the Great Scallop Pecten maximus. Sixty six individuals were exposed for 16 days to two successive dissolved Ba and Mo concentrations accurately differentiated by two different isotopic enrichments (97Mo, 95Mo; 135Ba, 137Ba). Soft tissue and shell isotopic composition were determined respectively by quantitative ICP-MS (Inductively Coupled Plasma Mass Spectrometer) and laser ablation ICP-MS. Results from Ba enrichment indicate the direct incorporation of dissolved Ba into the shell in proportion to the levels in the water in which they grew with a 68 day delay. The low spike contributions and the low partition coefficient (DMo = 0.0049 ± 0.0013), show that neither the soft tissue nor the shell were significantly sensitive to Mo enrichment. These results eliminate direct Mo shell enrichment by the dissolved phase, and favour a trophic uptake that will be investigated using the successive isotopic enrichment approach developed in this study.
Keywords: Isotopes, Femtosecond laser ablation, Scallop shell, Barium, Molybdenum, Pecten maximus, Tracers, Biogeochemical cycle,
Programme: 1090
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Christophe Barbraud, Karine Delord, Fabrice Le Bouard, Roald Harivel, Jérémie Demay, Adrien Chaigne, Thierry Micol. (2021). Seabird population changes following mammal eradication at oceanic Saint-Paul Island, Indian Ocean (Vol. 63).
Abstract: The eradication of invasive mammals on islands is important for protecting seabird populations and insular ecosystems. However, the impacts of such eradications are insufficiently known because monitoring of potentially beneficiary species is often sporadic and limited. We performed a survey of all seabird species on Saint-Paul Island, southern Indian Ocean, 20 years after successful eradication of invasive black rat (Rattus rattus) and European rabbit (Oryctolagus cuniculus). Using complementary sampling designs including adaptive cluster sampling, stratified random sampling and entire sampling, we estimated population changes and colonization by new seabird species. A total of 13 seabird species were found breeding on Saint-Paul post-eradication compared to six before the eradication. Among the seven species that colonized the island, five (MacGillivray’s prion Pachyptila macgillivrayi, fairy prion P. turtur, white-bellied storm petrel Fregetta grallaria, Antarctic tern Sterna vittata, sooty tern Onychoprion fuscatus) had relictual populations breeding on a nearby islet, and one (brown skua Catharacta antarctica) was a new breeding species. We also found breeding subantarctic little shearwaters Puffinus elegans. For species that were breeding on the Saint Paul pre-eradication, the mean annual population growth rate was 1.030 ± 0.093 (SE). Species known to be vulnerable to rat predation (prions, great-winged petrel Pterodroma macroptera, flesh-footed shearwater Puffinus carneipes, subantarctic little shearwater, white-bellied storm petrel, Antarctic tern) had the highest population growth rates. Two decades after the eradication of invasive mammals on a remote oceanic island, seabird populations were high beneficiaries. These findings further highlight the importance of invasive mammal eradication on islands as a conservation tool. Results are encouraging for the planned eradication of invasive mammals from nearby Amsterdam Island, and suggest this will mainly benefit terns and small burrowing petrels.
Keywords: Island restoration Petrels Population growth rate Rats Shearwaters Terns
Programme: 109
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Jenouvrier Stéphanie, Holland Marika, Stroeve Julienne, Barbraud Christophe, Weimerskirch Henri, Serreze Mark, Caswell Hal, . (2012). Effects of climate change on an emperor penguin population: analysis of coupled demographic and climate models
. Glob Chang Biol, 18(9), 2756–2770.
Abstract: Sea ice conditions in the Antarctic affect the life cycle of the emperor penguin (Aptenodytes forsteri). We present a population projection for the emperor penguin population of Terre Adélie, Antarctica, by linking demographic models (stage-structured, seasonal, nonlinear, two-sex matrix population models) to sea ice forecasts from an ensemble of IPCC climate models. Based on maximum likelihood capture-mark-recapture analysis, we find that seasonal sea ice concentration anomalies (SICa) affect adult survival and breeding success. Demographic models show that both deterministic and stochastic population growth rates are maximized at intermediate values of annual SICa, because neither the complete absence of sea ice, nor heavy and persistent sea ice, would provide satisfactory conditions for the emperor penguin. We show that under some conditions the stochastic growth rate is positively affected by the variance in SICa. We identify an ensemble of five general circulation climate models whose output closely matches the historical record of sea ice concentration in Terre Adélie. The output of this ensemble is used to produce stochastic forecasts of SICa, which in turn drive the population model. Uncertainty is included by incorporating multiple climate models and by a parametric bootstrap procedure that includes parameter uncertainty due to both model selection and estimation error. The median of these simulations predicts a decline of the Terre Adélie emperor penguin population of 81% by the year 2100. We find a 43% chance of an even greater decline, of 90% or more. The uncertainty in population projections reflects large differences among climate models in their forecasts of future sea ice conditions. One such model predicts population increases over much of the century, but overall, the ensemble of models predicts that population declines are far more likely than population increases. We conclude that climate change is a significant risk for the emperor penguin. Our analytical approach, in which demographic models are linked to IPCC climate models, is powerful and generally applicable to other species and systems.
Keywords: IPCC, sea ice, seabirds, stochastic climate forecast, stochastic matrix population model, uncertainties,
Programme: 109
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Chisham G, Freeman M P, Abel G A, Bristow W A, Marchaudon A, Ruohoniemi J M, Sofko G J, . (2009). Spatial distribution of average vorticity in the high-latitude ionosphere and its variation with interplanetary magnetic field direction and season
. J. Geophys. Res., 114(A9), A09301–.
Abstract: We present a technique to measure the magnetic field-aligned vorticity of mesoscale plasma flows in the F region ionosphere using line-of-sight velocity measurements made by the Super Dual Auroral Radar Network (SuperDARN). Vorticity is often used as a proxy for magnetic field-aligned current (FAC) intensity in the ionosphere but also provides information about turbulent processes in the ionosphere and magnetosphere. Using 6 years (2000–2005 inclusive) of vorticity measurements made by six SuperDARN radars in the Northern Hemisphere, we have compiled, for the first time, maps of average vorticity across the northern polar ionosphere. These maps have been subdivided according to different seasonal and interplanetary magnetic field (IMF) conditions. The variations in the morphology of the vorticity maps with IMF direction match very closely those seen in maps of average FAC intensity (determined using different methods and instrumentation), suggesting that vorticity is a good proxy for FAC in an averaged sense. The variations in the morphology of the vorticity maps with season show differences from those seen in the FAC maps, illustrating that ionospheric conductance plays a major role in determining the differences between measurements of vorticity and FAC.
Keywords: ionosphere, vorticity, field-aligned current, 2431 Ionosphere: Ionosphere/magnetosphere interactions, 2409 Ionosphere: Current systems, 2437 Ionosphere: Ionospheric dynamics, 2494 Ionosphere: Instruments and techniques, 2721 Magnetospheric Physics: Field-aligned currents and current systems,
Programme: 312;911
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Lukianova R, Hanuise C, Christiansen F, . (2008). Asymmetric distribution of the ionospheric electric potential in the opposite hemispheres as inferred from the SuperDARN observations and FAC-based convection model
. 1364-6826, 70(18), 2324–2335.
Abstract: We compare the SuperDARN convection patterns with the predictions of a new numerical model of the global distribution of ionospheric electric potentials. The model utilizes high-precision statistical maps of field-aligned currents (FAC) derived from measurements made by polar-orbiting low-altitude satellites. Both the solar and auroral precipitation contributions are included in order to derive the ionospheric conductance. Taking into account the electrodynamic coupling of the opposite hemispheres, the model allows one to obtain the convection patterns developed simultaneously in both hemispheres for given input parameters. SuperDARN, with its database containing global northern and southern convection maps, provides the unique opportunity to compare the model predictions of electric fields with observations. In the present study we focus on the effect of significant interhemispheric asymmetry governed by the IMF clock angle and solar zenith angle. We calculate the convection patterns for specific cases caused by the sign of BY and season and demonstrate the capability of the FAC-based model reproduce the radar observations. The simulation confirms that the solar zenith angle should be linked to the IMF clock angle to fully characterize the convection patterns. The model predicts that the cross-polar cap potential drop is regularly larger in the winter hemisphere than in the summer hemisphere.
Keywords: Ionosphere, Convection, Field-aligned currents, SuperDARN,
Programme: 312;911
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