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Welcker Jorg, Chastel Olivier, Gabrielsen Geir W, Guillaumin Jerome, Kitaysky Alexander S, Speakman John R, Tremblay Yann, Bech Claus, . (2013). Thyroid Hormones Correlate with Basal Metabolic Rate but Not Field Metabolic Rate in a Wild Bird Species
. PLOS ONE, 8(2).
Abstract: Thyroid hormones (TH) are known to stimulate in vitro oxygen consumption of tissues in mammals and birds. Hence, in many laboratory studies a positive relationship between TH concentrations and basal metabolic rate (BMR) has been demonstrated whereas evidence from species in the wild is scarce. Even though basal and field metabolic rates (FMR) are often thought to be intrinsically linked it is still unknown whether a relationship between TH and FMR exists. Here we determine the relationship between the primary thyroid hormone triiodothyronine (T3) with both BMR and FMR in a wild bird species, the black-legged kittiwake (Rissa tridactyla). As predicted we found a strong and positive relationship between plasma concentrations of T3 and both BMR and mass-independent BMR with coefficients of determination ranging from 0.36 to 0.60. In contrast there was no association of T3 levels with either whole-body or mass-independent FMR (R2 = 0.06 and 0.02, respectively). In accordance with in vitro studies our data suggests that TH play an important role in modulating BMR and may serve as a proxy for basal metabolism in wild birds. However, the lack of a relationship between TH and FMR indicates that levels of physical activity in kittiwakes are largely independent of TH concentrations and support recent studies that cast doubt on a direct linkage between BMR and FMR.
Programme: 330
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Monternier PA. (2015). Flexibilité mitochondrial au cours du jeûne. Etude chez le caneton de barbarie et le poussin de manchot royal.
Abstract: Throughout their life, wild species face periods of food-deprivation that induce energy trade-offs between survival, growth and reproduction. These fasting periods occur either when food availability is lacking due to adverse climatic conditions or because individuals are engaged in biological processes that prevent food access. This later reason is particularly well illustrated in the king penguin (Aptenodytes patagonicus), a sea bird that has to moult and reproduce on shore whereas he feed exclusively at sea. Moreover king penguin chicks exhibit exceptional survival capacities during their first year of life when they experience a long period of fast in winter. Thus, this species that lives in sub-Antarctic latitudes, is exposed to environmental and physiological energy constraints during food shortage periods.
Since king penguins are endotherms, they need to maintain their body temperature at high level despite variations of ambient temperature. Thus thermoregulation is one of the most expensive process and skeletal muscles account for the greater part of heat production in birds.
Several studies showed that despite long term cold exposure, energy expenditure of fasting birds decreases allowing energy savings and especially protein sparing. Since skeletal muscles have high implications in energy expenditure and heat production the question of their implication in energy saving mechanisms arises. During my PhD project I studied skeletal muscle metabolism through mitochondrial efficiency. These sub-cellular organelles are the last effectors of energy transduction from nutrient into ATP, an usable energy for cells. Our hypothesis is based on the flexibility of mitochondrial efficiency as a regulator of energy sparing mechanisms which would explain long term resistance to starvation.
My studies were conducted in a wild species, the king penguin chicks, that are naturally acclimated to cold environment and experienced long term fasting stage. To further investigate mitochondrial plasticity in response to energy constraints, I developed several experimental procedures in controlled conditions on a laboratory model (Muscovy ducklings).
The flexibility of mitochondrial efficiency observed in these two avian species suggests that this mechanism could highly decrease the cost of energy production during food-deprivation period even when birds were exposed to cold. Although, mitochondrial efficiency improvement was found in both species, it seems to depend on the phenotype and/or activity of skeletal muscles.
Programme: 131
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Savarino J, Kaiser J, Morin S, Sigman D M, Thiemens M H, . (2007). Nitrogen and oxygen isotopic constraints on the origin of atmospheric nitrate in coastal Antarctica
. Atmospheric Chemistry and Physics, 7(8), 1925–1945.
Abstract: Throughout the year 2001, aerosol samples were collected continuously for 10 to 15 days at the French Antarctic Station Dumont d'Urville DDU) (66 degrees 40' S, 140 degrees 01' E, 40m above mean sea level). The nitrogen and oxygen isotopic ratios of particulate nitrate at DDU exhibit seasonal variations that are among the most extreme observed for nitrate on Earth. In association with concentration measurements, the isotope ratios delineate four distinct periods, broadly consistent with previous studies on Antarctic coastal areas. During austral autumn and early winter March to mid-July), nitrate concentrations attain a minimum between 10 and 30 ng m(-3) referred to as Period 2). Two local maxima in August (55 ng m(-3)) and November/December (165 ng m(-3)) are used to assign Period 3 (mid-July to September) and Period 4 October to December). Period 1 January to March) is a transition period between the maximum concentration of Period 4 and the background concentration of Period 2. These seasonal changes are reflected in changes of the nitrogen and oxygen isotope ratios. During Period 2, which is characterized by background concentrations, the isotope ratios are in the range of previous measurements at midlatitudes: delta O-18(vsmow)=(77.2 8.6)parts per thousand; Delta O-17=(29.8 4.4)parts per thousand; delta N-15(air)=(- 4.4 5.4)parts per thousand mean one standard deviation). Period 3 is accompanied by a significant increase of the oxygen isotope ratios and a small increase of the nitrogen isotope ratio to delta O-18(vsmow)=( 98.8 13.9)parts per thousand; Delta O-17=(38.8 4.7)parts per thousand and delta N-15(air)=(4.3 8.20 parts per thousand). Period 4 is characterized by a minimum N-15/N-14 ratio, only matched by one prior study of Antarctic aerosols, and oxygen isotope ratios similar to Period 2: delta O-18(vsmow)=(77.2 7.7)parts per thousand; Delta O-17=(31.1 3.2)parts per thousand; delta N-15(air)=(- 32.7 8.4)parts per thousand. Finally, during Period 1, isotope ratios reach minimum values for oxygen and intermediate values for nitrogen: delta O-18(vsmow)= 63.2 2.5 parts per thousand; Delta O-17= 24.0 1.1 parts per thousand; delta N-15(air)=- 17.9 4.0 parts per thousand). Based on the measured isotopic composition, known atmospheric transport patterns and the current understanding of kinetics and isotope effects of relevant atmospheric chemical processes, we suggest that elevated tropospheric nitrate levels during Period 3 are most likely the result of nitrate sedimentation from polar stratospheric clouds (PSCs), whereas elevated nitrate levels during Period 4 are likely to result from snow re-emission of nitrogen oxide species. We are unable to attribute the source of the nitrate during periods 1 and 2 to local production or long-range transport, but note that the oxygen isotopic composition is in agreement with day and night time nitrate chemistry driven by the diurnal solar cycle. A precise quantification is difficult, due to our insufficient knowledge of isotope fractionation during the reactions leading to nitrate formation, among other reasons.
Programme: 414
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. (2018). Early stage litter decomposition across biomes (Vol. 628-629).
Keywords: Carbon turnover Green tea Rooibos tea Tea bag TeaComposition initiative
Programme: 136
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Testut L, Birol F, Delebecque C, . (2012). Regional Tidal Modeling and Evaluation of Jason-2 Tidal Geophysical Correction
. Marine Geodesy, 35(sup1), 299–313.
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Barral H, Genthon C, Trouvilliez A, Brun C, Amory C, . (2014). TC, 8(5), 1905–1919.
Abstract: Three years of blowing snow observations and associated meteorology along a 7-m mast at site D17 in coastal Adelie Land are presented. The observations are used to address 3 atmospheric moisture issues related to the occurrence of blowing snow, a feature which largely affects many regions of Antarctica: 1) Blowing snow sublimation raises close to saturation the moisture content of the surface atmosphere, and atmospheric models and meteorological analyzes that do not carry blowing snow parameterizations areaffected by a systematic dry bias; 2) While snowpack modeling with a parameterization of surface snow erosion by wind can reproduce the variability of snow accumulation and ablation, ignoring the high levels of atmospheric moisture content associated with blowing snow results in overestimating surface sublimation affecting the energy budget of the snow-pack; 3) the well-known profile method to calculate turbulent moisture fluxes is not applicable when blowing snow occurs, because moisture gradients are weak due to blowing snow sublimation, and the impact of measurement uncertainties are strongly amplified in case of strong winds.
Keywords: Antarctica, Snowpack, Surface Mass Balance, Katabatic flow, Blowing snow, Sublimation, Latent Heat Fluxes, Moisture, Observation, Modelling, Profile method,Monin and Obukhov similarity theory, Uncertainty propagation
Programme: 1013
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Barral H, Genthon C, Trouvilliez A, Brun C, Amory C, . (2014). The Cryosphere Discuss., 8(3), 2759–2798.
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Allcock A Louise, Barratt Iain, Elaume Marc, Linse Katrin, Norman Mark D, Smith Peter J, Steinke Dirk, Stevens Darren W, Strugnell Jan M, . (2011). Cryptic speciation and the circumpolarity debate: A case study on endemic Southern Ocean octopuses using the COI barcode of life
. Deep Sea Res. Part II Top. Stud. Oceanogr., 58(1-2), 242–249.
Keywords: DNA barcoding, Pareledone, Ring species, Circumpolarity,
Programme: 1124
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Paul Tixier, Nicolas Gasco, Jared R. Towers, Christophe Guinet. (2021). Killer whales of the Crozet Archipelago and adjacent waters: photo-identification catalogue, population status and distribution in 2020.
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. (2010). Candidate models for the IGRF 11th generation making use of extrapolated observatory data
. Earth Planets and Space, 62, 745–751.
Abstract: Three candidate models are produced in response to the call for IGRF-11 models. A main field model around epoch 2005.0 is based on one year of Oersted and CHAMP measurements, and is proposed for the definitive model for epoch 2005.0. A main field model around epoch 2009.5, based on two months of CHAMP measurements and extrapolated to 2010.0, is proposed as a main field model for epoch 2010.0. A secular variation model valid for 2010.0-2015.0, based on the extrapolation through exponential
smoothing of observatory monthly mean values, is proposed as a predictive secular variation model. Comparison of similar extrapolations made for previous IGRF generations with actual observations are presented and discussed.
Programme: 139;905
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