Simon, N.S.C.; Neumann, E.-R.; Bonadiman, C.; Coltorti, M.; Delpech, G.; Gregoire, M.; Widom, E. (2008). Ultra-refractory Domains in the Oceanic Mantle Lithosphere Sampled as Mantle Xenoliths at Ocean Islands. Journal of petrology, 49(6), 1223–1251.
Abstract: Many peridotite xenoliths sampled at ocean islands appear to have strongly refractory major element and modal compositions. To better constrain the chemistry, abundance and origin of these ultra-refractory rocks we compiled a large number of data for xenoliths from nine groups of ocean islands. The xenoliths were filtered petrographically for signs of melt infiltration and modal metasomatism, and the samples affected by these processes were excluded. The xenolith suites from most ocean islands are dominated by ultra-refractory harzburgites. Exceptions are the Hawaii and Tahiti peridotites, which are more fertile and contain primary clinopyroxene, and the Cape Verde suite, which contains both ultra-refractory and more fertile xenoliths. Ultra-refractory harzburgites are characterized by the absence of primary clinopyroxene, low whole-rock Al2O3, CaO, FeO/MgO and heavy rare earth element (HREE) concentrations, low Al2O3 in orthopyroxene (generally < 3 wt %), high Cr-number in spinel (0{middle dot}3-0{middle dot}8) and high forsterite contents in olivine (averages > 91{middle dot}5). They are therefore on average significantly more refractory than peridotites dredged and drilled from mid-ocean ridges and fracture zones. Moreover, their compositions resemble those of oceanic forearc peridotites. The formation of ultra-refractory ocean island harzburgites requires potential temperatures above those normally observed at modern mid-ocean ridges, and/or fluid fluxed conditions. Some ultra-refractory ocean island harzburgites give high Os model ages (up to 3300 Ma), showing that their formation significantly pre-dates the oceanic crust in the area. A genetic relationship with the host plume is considered unlikely based on textural observations, equilibration temperatures and pressures, inferred physical properties, and the long-term depleted Os and Sr isotope compositions of some of the harzburgites. Although we do not exclude the possibility that some ultra-refractory ocean island harzburgites have formed at mid-ocean ridges, we favor a model in which they formed in a process spatially and temporally unrelated to the formation of the oceanic plate and the host plume. As a result of their whole-rock compositions, ultra-refractory harzburgites have a very high solidus temperature at a given pressure, low densities and very high viscosities, and will tend to accumulate at the top of the convecting mantle. They may be preserved as fragments in the convecting mantle over long periods of time and be preferentially incorporated into newly formed lithosphere.
Programme: 444
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Rønning, B.; Moe, B.; Chastel, O.; Broggi, J.; Langset, M.; Bech, C. (2008). Metabolic adjustments in breeding female kittiwakes ( Rissa tridactyla ) include changes in kidney metabolic intensity. Journal of Comparative Physiology B: Biochemical, Systemic, and Environmental Physiology, 178(6), 779–784.
Abstract: Abstract Black-legged kittiwakes (BLKIs) reduce self-maintenance cost through reductions in mass-specific basal metabolic rate (BMR), body mass and the size of visceral organs during the chick-rearing period. In the present study, we measured kidney in vitro oxygen consumption and plasma 3,3?,5-triiodo-l-thyronine (T3) levels of incubating and chick-rearing female BLKIs, to test whether the decrease in BMR is caused mainly by decreased metabolic intensity or simply by reductions in the size of organs with high metabolic intensity. Body mass and body condition were lower in chick-rearing birds compared with the incubating birds. In contrast to the previous findings, however, the kidney mass did not differ between the two breeding stages. Plasma T3 levels decreased substantially during the breeding season, indicating a reduction in BMR. Over the same period, kidney mass-specific oxygen consumption decreased (by 17.2%) from the incubating to the chick-rearing stage. Thus, the reduction in BMR found in breeding BLKIs seems partly explained by adjustments in metabolic intensity of visceral organs. Lowered metabolic intensity of visceral organs would permit increased allocation of energy to offspring at the expense of their own self-maintenance.
Programme: 330
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Halsey, L.G. Butler, P.J., Fahlman, A., Bost, C.-A., Woakes, A.J., Handrich, Y. (2008). Modelling the marine resources required to raise a king penguin chick in differing environments: an energetics approach. Physiol. Biochem. Zool., 81(6), 856–867.
Abstract: Accurate estimates of penguin energetics would represent an important contribution to our understanding of the trophodynamics of the Southern Ocean ecosystem and our ability to predict effects of environmental change on these species. We used the heart rate–rate of oxygen consumption technique to estimate rate of energy expenditure in adult king penguins raising a chick, in combination with data from the literature on changes in adult mass, chick energy requirements, and prey energy density. Our model estimated a variety of energetic costs and quantities of prey consumption related to raising a king penguin chick during the austral summer. The total energy requirements of a king penguin chick at the Crozet Archipelago from hatching until reaching a mass of 8 kg 90 d later is 271 MJ, representing the consumption of 38.4 kg of myctophid fish. A successfully breeding male requires 0.78 kg d-1 of fish during the entirety of the incubation period and 1.14 kg d-1 during the subsequent 90 d of chick rearing. Assuming the same energy requirements for females, the estimated 580,000 pairs of king penguins that breed successfully at Crozet each year, together with their chicks, consume a total of around 190,000 tons of fish during the incubation and summer rearing periods combined. If, due to depletion of fish stocks, the diet of breeders and chicks during the summer becomes identical to the typical diet of adults during the austral winter, the mass of prey required by both adults and chicks combined (where the chick still reaches 8 kg after 90 d) would increase by more than 25%.
Programme: 394
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Maraldi C., M. Mongin, R. Coleman and L. Testut. (2009). The influence of lateral mixing on a phytoplankton bloom : Distributionin the Kerguelen Plateau. Deep Sea Res. Part I Oceanogr. Res. Pap., 56(6), 963–973.
Abstract: A very unique phytoplankton bloom appears every year during the austral spring/summer in the Northern Kerguelen Plateau region. The Kerguelen Ocean and Plateau compared Study (KEOPS) showed that an increase in subsurface iron coming up from the seafloor through vertical mixing was responsible for the observed increase in chlorophyll-a above the plateau. We demonstrate that the bloom pattern is not a simple increase of biomass over shallow water: it is strongly influenced by the bathymetry and its spatial extent controlled by strong currents around the plateau. Here we focus on the lateral mixing process to find explanations for the particular shape of the bloom. We use the Smagorinsky (1963) formula to estimate and map fields of lateral mixing time scales ( ) due to barotropic tidal currents, barotropic atmospheric forced currents, Ekman and geostrophic velocities. Results show that short time scale mixing is strongly influenced by the tidal process while the other processes have minor influences. Comparisons of lateral mixing coefficient and satellite chlorophyll-a images show that the spatial pattern of the bloom seems to be delimited by a barrier of high lateral mixing that is essentially due to tides. This emphasises the role played by the tides over the Kerguelen Plateau, in supplying iron to the phytoplankton and by containing the horizontal shape of the bloom. This is one of the first times such a link has been demonstrated, which has implications for the study of iron advection in the ocean.
Programme: 688
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Barthélémy, M.; Lilensten, J.; Pitout, F.; Simon Wedlund, C.; Thissen, R.; Lorentzen, D.; Sigernes, F.; Moen, J.; Gronoff, G.; McCrea, I.; Rothkael, H.; Ménager, H.; Aruliah, A. (2011). Polarisation in the auroral red line during coordinated EISCAT Svalbard Radar/optical experiments. ANGEO, 29(6), 1101–1112.
Abstract: The polarisation of the atomic oxygen red line in the Earth's thermosphere is observed in different configurations with respect to the magnetic field line at high latitude during several coordinated Incoherent Scatter radar/optical experiment campaigns. When pointing northward with a line-of-sight nearly perpendicular to the magnetic field, we show that, as expected, the polarisation is due to precipitated electrons with characteristic energies of a few hundreds of electron Volts. When pointing toward the zenith or southward with a line-of-sight more parallel to the magnetic field, we show that the polarisation practically disappears. This confirms experimentally the predictions deduced from the recent discovery of the red line polarisation. We show that the polarisation direction is parallel to the magnetic field line during geomagnetic activity intensification and that these results are in agreement with theoretical work.
Programme: 1026
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Jenouvrier Stéphanie, Caswell Hal, Barbraud Christophe, Weimerskirch Henri, . (2010). Mating behavior, population growth, and the operational sex ratio: a periodic two-sex model approach.
. Am. Nat., 175(6), 739–52.
Abstract: We present a new approach to modeling two-sex populations, using periodic, nonlinear two-sex matrix models. The models project the population growth rate, the population structure, and any ratio of interest (e.g., operational sex ratio). The periodic formulation permits inclusion of highly seasonal behavioral events. A periodic product of the seasonal matrices describes annual population dynamics. The model is nonlinear because mating probability depends on the structure of the population. To study how the vital rates influence population growth rate, population structure, and operational sex ratio, we used sensitivity analysis of frequency-dependent nonlinear models. In nonlinear two-sex models the vital rates affect growth rate directly and also indirectly through effects on the population structure. The indirect effects can sometimes overwhelm the direct effects and are revealed only by nonlinear analysis. We find that the sensitivity of the population growth rate to female survival is negative for the emperor penguin, a species with highly seasonal breeding behavior. This result could not occur in linear models because changes in population structure have no effect on per capita reproduction. Our approach is applicable to ecological and evolutionary studies of any species in which males and females interact in a seasonal environment.
Keywords: Animals, Female, Male, Models, Biological, Population Growth, Sex Ratio, Sexual Behavior, Animal, Spheniscidae,
Programme: 109
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Raymond Ben, Shaffer Scott A, Sokolov Serguei, Woehler Eric J, Costa Daniel P, Einoder Luke, Hindell Mark, Hosie Graham, Pinkerton Matt, Sagar Paul M, Scott Darren, Smith Adam, Thompson David R, Vertigan Caitlin, Weimerskirch Henri, . (2010). Shearwater foraging in the Southern Ocean: the roles of prey availability and winds.
. PloS one, 5(6), e10960.
Abstract: BACKGROUND: Sooty (Puffinus griseus) and short-tailed (P. tenuirostris) shearwaters are abundant seabirds that range widely across global oceans. Understanding the foraging ecology of these species in the Southern Ocean is important for monitoring and ecosystem conservation and management. METHODOLOGY/PRINCIPAL FINDINGS: Tracking data from sooty and short-tailed shearwaters from three regions of New Zealand and Australia were combined with at-sea observations of shearwaters in the Southern Ocean, physical oceanography, near-surface copepod distributions, pelagic trawl data, and synoptic near-surface winds. Shearwaters from all three regions foraged in the Polar Front zone, and showed particular overlap in the region around 140 degrees E. Short-tailed shearwaters from South Australia also foraged in Antarctic waters south of the Polar Front. The spatial distribution of shearwater foraging effort in the Polar Front zone was matched by patterns in large-scale upwelling, primary production, and abundances of copepods and myctophid fish. Oceanic winds were found to be broad determinants of foraging distribution, and of the flight paths taken by the birds on long foraging trips to Antarctic waters. CONCLUSIONS/SIGNIFICANCE: The shearwaters displayed foraging site fidelity and overlap of foraging habitat between species and populations that may enhance their utility as indicators of Southern Ocean ecosystems. The results highlight the importance of upwellings due to interactions of the Antarctic Circumpolar Current with large-scale bottom topography, and the corresponding localised increases in the productivity of the Polar Front ecosystem.
Keywords: Animals, Biodiversity, Birds, Birds: physiology, Ecology, Marine Biology, Oceans and Seas, Predatory Behavior, Wind,
Programme: 109
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Angelier Frédéric, Wingfield John C, Weimerskirch Henri, Chastel Olivier, . (2010). Hormonal correlates of individual quality in a long-lived bird: a test of the 'corticosterone-fitness hypothesis'.
. Biology letters, 6(6), 846–9.
Abstract: Measuring individual quality in vertebrates is difficult. Focusing on allostasis mechanisms may be useful because they are functionally involved in the ability of an individual to survive and reproduce in its environment. Thus, a rise in stress hormones levels (corticosterone) occurs when an organism has to cope with challenging environmental conditions. This has recently led to the proposal of the 'cort-fitness hypothesis', which suggests that elevated baseline corticosterone levels should be found in individuals of poor quality that have difficulty coping with their environment. We tested this hypothesis by comparing an integrative measure of individual quality to baseline corticosterone in black-browed albatrosses (Thalassarche melanophrys). We found that individual baseline corticosterone levels were related to individual quality and highly repeatable from one breeding season to the next. Importantly, this relationship was found in males, but not in females. Therefore, we suggest that the relationship between quality and baseline corticosterone levels may depend on the environmental and energetic constraints that individuals have to cope with.
Keywords: Animals, Birds, Birds: blood, Birds: physiology, Breeding, Corticosterone, Corticosterone: blood, Female, Genetic Fitness, Male, Models, Biological, Reproduction, Reproduction: physiology, Seasons,
Programme: 109
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Welcker Jorg, Harding Ann M A, Kitaysky Alexander S, Speakman John R, . (2009). Daily energy expenditure increases in response to low nutritional stress in an Arctic-breeding seabird with no effect on mortality
. Functional Ecology, 23(6), 1081–1090.
Abstract: 1. The regulation of energy expenditure in relation to food availability and its consequences for individual fitness in free-ranging animals are poorly understood. Increased daily energy expenditure (DEE) may be viewed as the result of two different processes: expenditure may be forced
Programme: 388
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Barbraud Christophe, Thiebot Jean-Baptiste, . (2009). On the importance of estimating detection probabilities from at-sea surveys of flying seabirds
. J. Avian Biol., 40(6), 584–590.
Abstract: The primary and accepted method used to estimate seabird densities at sea from ships is the strip transect method, designed to correct for the effect of random directional bird movement relative to that of the ship. However, this method relies on the critical assumption that all of the birds within the survey strip are detected. We used the distance sampling method from line-transects to estimate detection probability of a number of species of flying seabirds, and to test whether distance from the ship and bird body size affected detectability. Detection probability decreased from 0.987 (SE=0.029) to 0.269 (SE=0.035) with increasing strip half-width from 100 to 1400 m. Detection probability also varied between size-groups of species with strip half-width. For all size-groups, this probability was close to 1 for strip half-width of 100 m, but was 0.869 (SE=0.115), 0.725 (SE=0.096) and 0.693 (SE=0.091) for strip half-width of 300 m, a typical strip width used in seabird surveys, for respectively large, medium and small size flying seabirds. For larger strip half-width, detection probability was higher for large sized species, intermediate for medium sized species and lower for smaller sized species. For strip half-width larger than 100 m we suggest that more attention should be paid to testing the assumption of perfect detectability, because abundance estimates may be underestimated when this assumption is violated. Finally, the effect of the speed of travel of flying seabird on the detection probability was estimated in a simulation study, which suggests that detection probability was underestimated with increasing flying speed.
Programme: 109
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