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Thiebot JB, Ito K, Raclot T, Poupart T, Kato A, Ropert-Coudert Y, Takahashi A. (2016). On the significance of Antarctic jellyfish as food for Adelie penguins, as revealed by video-loggers. MARINE BIOLOGY, 163(5), 108.
Abstract: Concern of pelagic gelatinous organisms taking over perturbed marine ecosystems has led to a recent increase in research into this group. However, the significance of this group as prey remains challenging to assess, and hence, gelatinous consumers are often depicted incorrectly as dead ends of pelagic food webs. In the Southern Ocean, where a shift in trophic webs may favour gelatinous animals, we video-monitored prey intake of a key predator. Twenty-eight chick-rearing Adélie penguins Pygoscelis adeliae from Dumont d’Urville station (66°40′S, 140°01′E) were instrumented with miniaturized video loggers in 2014–2015. Among other items (krill, fish), 101 gelatinous organisms (n = 79 jellyfish, 6 salps and 16 unidentified) were observed on 13 of 21 exploitable video footages (total: 59 h). Importantly, 65.3 % of gelatinous organisms were attacked, but among them salps were not attacked. Attacks on jellyfish were significantly associated with the visible presence of the jellyfish’s gonad. Jellyfish were encountered at an average depth of 26.2 ± 10.4 m, significantly shallower than krill. Attacks occurred mostly during bottom, but also descent or ascent dive phases. Concomitant GPS location for four birds revealed that attacks on jellyfish occurred above the shelf, 35 km north from the colony, where sea ice concentration reached 88 %. These results indicate that Adélie penguins occasionally feed on jellyfish, even though other prey types are also available. Refining our perception of scyphozoans’ niche may thus help anticipate the functional response of the food webs to the extensive changes witnessed in the Antarctic environment.
Programme: 1091
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Picard, G et al. (2016). Spectral albedo and derive specific surface area of snow at Dome C, 2012-2015.
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J. Bock, J. Savarino, and G. Picard. (2016). Air – snow exchange of nitrate: a modelling approach to investigate physicochemical processes in surface snow at Dome C, Antarctica. ATMOSPHERIC CHEMISTRY AND PHYSICS, 16(19), 12531–12550.
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Casado M, Landais A, Masson-Delmotte V, Genthon C, Kerstel E, Kassi S, Arnaud L, Picard G, Prie F, Cattani O, Steen-Larsen H-C, Vignon E, Cermak P, . (2016). Continuous measurements of isotopic composition of water vapour on the East Antarctic Plateau. ATMOSPHERIC CHEMISTRY AND PHYSICS, 16(13), 8521–8538.
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G. Picard, Q. Libois, L. Arnaud, G. Vérin, M. Dumont . (2016). Development and calibration of an automatic spectral albedometer to estimate near-surface snow SSA time series. The Cryosphere, 10(3), 1297–1316.
Abstract: Spectral albedo of the snow surface in the visible/near-infrared range has been measured for 3 years by an automatic spectral radiometer installed at Dome C (75°?S, 123°?E) in Antarctica in order to retrieve the specific surface area (SSA) of superficial snow. This study focuses on the uncertainties of the SSA retrieval due to instrumental and data processing limitations. We find that when the solar zenith angle is high, the main source of uncertainties is the imperfect angular response of the light collectors. This imperfection introduces a small spurious wavelength-dependent trend in the albedo spectra which greatly affects the SSA retrieval. By modeling this effect, we show that for typical snow and illumination conditions encountered at Dome C, retrieving SSA with an accuracy better than 15?% (our target) requires the difference of response between 400 and 1100?nm to not exceed 2?%. Such a small difference can be achieved only by (i) a careful design of the collectors, (ii) an ad hoc correction of the spectra using the actual measured angular response of the collectors, and (iii) for solar zenith angles less than 75°. The 3-year time series of retrieved SSA features a 3-fold decrease every summer which is significantly larger than the estimated uncertainties. This highlights the high dynamics of near-surface SSA at Dome C.
Programme: 1110
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Macelloni Giovanni, Leduc-Leballeur Marion, Brogioni Marco, Ritz Catherine, Picard Ghislain, . (2016). Analyzing and modeling the SMOS spatial variations in the East Antarctic Plateau. REMOTE SENSING OF ENVIRONMENT, 180, 193–204.
Abstract: The SMOS brightness temperature (TB) collected on the East Antarctic Plateau revealed spatial signatures at L-band that have never before been observed when only higher-frequency passive microwave observations were available, and this has opened up a new field of research. Because of the much greater penetration depth, modeling the microwave ice sheet emission requires taking into account not only snow conditions on the surface, but should also include glaciological information. Even if the penetration depth of the L-band is not well known due to the uncertainty on the imaginary part of the ice permittivity, it is likely to be of the order of several hundreds of meters, which means that the temperature of the ice over a depth of nearly 1000 m influences the emission. Over such a depth, the temperature is related to both the surface conditions and to the ice sheet thickness, which in turn depends on the bedrock topography and on other glaciological variables. The present paper aims to provide a thorough theoretical explanation of the observed TB spatial variation close to the Brewster angle at vertical polarization, in order to limit the effect of surface and vertical density variability in the firn. In order to provide reliable inputs to the microwave emission models used for simulating TB data, an in-depth analysis of the temperature profiles was performed by means of glaciological models. The comparison between simulated and observed data over three transects totalling 2000 km in East Antarctica pointed out that, whereas the emission models are capable of explaining the TB spatial variations of several kelvins (0.7 and 2.9 K), they are unable to predict its absolute value correctly. This study also shows that the main limiting factor in simulating low-frequency microwave data is the uncertainty in the currently available imaginary part of the ice permittivity.
Keywords: Antarctica, Ice sheet temperature, Microwave emission model, SMOS,
Programme: 902,1110
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Boulinier, T. (2016). Infectious diseases as a threat to albatrosses and petrels: from basic immuno-ecology to perspectives for conservation. Invited keynote speaker, 6th International Albatross and Petrel Conference, Barcelona, September 2016..
Abstract: Infectious diseases are a relatively neglected but potentially important threat to populations of albatrosses and petrels. This is notably so for species breeding in dense aggregations, which can be the subject of recurrent local epizooties, such as in the case of avian cholera in albatrosses of Amsterdam Island, in the Southern Indian Ocean. With regards to parasites and diseases, the life histories of albatrosses and petrels, with their very long lifespan and high site fidelity, also make them potentially interesting model systems to explore whether and how their immune system has evolved special features to protect them against potential recurrent exposure to parasites at the breeding site. In this context, I will present how basic immune-ecological investigations led us to some original findings about variations in the temporal persistence of maternal antibodies in birds, with some potential implications for conservation. More specifically, after finding that antibodies transmitted by the mother to the chick through the egg yolk can persist more than two months after hatching in the Cory’s shearwater, we have started to explore variability of this immune trait among seabird species and some possible application to conservation in the case of an infectious disease harming young albatross chicks. The results of this work, which implies collaborations with several groups of biologists, stress that the Procellariiforms may be very special with regard to their acquired immunity. They also open some promising venue for the use of vaccination in the wild in some critical situations. More generally, the findings highlight the interest of exploring the many ways wild populations have evolved to respond to the variability of the environment in which they have been living.
Programme: 1151
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Bazire, R. (2016). Mouvements de labbes sur l'île d'Amsterdam dans un contexte de circulation de l'agent du choléra aviaire et de la transmission aux albatrosses. Rapport de stage de Master 1 de l'Université de Montpellier, Master 'Biodiversité, Ecologie, Evolution', parcours 'Ingénierie en Écologie et en Gestion de la Biodiversité'..
Abstract: Les maladies ont de tout temps contribué à la fluctuation des populations animales et ont lepotentiel dans certains cas particuliers de causer de rapides déclins. La description et lacompréhension des facteurs qui affectent la circulation d’agents infectieux dans les populationsanimales, comme notamment la dynamique spatiale des hôtes, sont importantes d’un point devue de la conservation et il devient important de connaître l’état éco-épidémiologique de cessystèmes. Le succès reproducteur de la population d’albatros à bec jaune de l’île d’Amsterdamdans l’océan Indien est très mauvais d’une façon récurrente depuis une vingtaine d’années et laprésence de l’agent responsable du choléra aviaire, Pasteurella multocida, est susceptible d’enêtre la cause principale. Dans ce contexte, cette étude vise à explorer dans quelle mesure lesmouvements d’une espèce prédatrice et charognarde, le Labbe subantarctique, jouent un rôledans la circulation de l’agent pathogène. L’analyse des mouvements de cette espèce a permisde mettre en évidence la large distribution de l’activité d’individus dans les zones dereproduction des albatros à bec jaune, comprenant aussi une autre espèce d’albatros et demanchot. Les observations de terrain indiquent que les labbes sont très actifs dans ces zones etles utilisent à des fins alimentaires, en ouvrant et consommant des cadavres, des oeufs ou despoussins. Sachant que les labbes ont été montrés comme porteurs de la bactérie, leur rôle dansla circulation de l’agent pathogène pourrait ne pas être négligeable. Les mouvements observésn’ont néanmoins pas suggéré que les labbes fréquentent la zone de reproduction des albatrosd’Amsterdam, au sommet de l’île, ce qui limite sans doute les risques de dissémination à cetteespèce endémique menacée. L’utilisation de loggers GPS-UHF permettant l’acquisition dedonnées sans la contrainte de la recapture des individus est prometteuse et il est discutél’optimisation de l’acquisition future de données.
Programme: 1151
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Bourret, V., Tornos, J., Jaeger, A., Gamble, A., Ramos, R., Kada, S., Bazire, R., Le Berre, H., Giraud, N., Thibault, E., Gantelet, H., Thiebot, J.-B., Barbraud, C., Delord, K., Weimerskirch, H., Garnier, R. & Boulinier, T. (2016). Testing a vaccine against avian cholera in albatrosses: combining observational and experimental data in a remote seabird community. Oral communication, 6th International Albatross and Petrel Conference, Barcelona, September 2016..
Abstract: Avian cholera, caused by the bacterium Pasteurella multocida, is suspected to cause substantial chick mortality in dense albatross colonies on Amsterdam Island (Southern Indian Ocean). Given their long life span and site fidelity, a vaccination programme aimed at covering a significant proportion of the population could be fruitfully applied to albatrosses. Further, understanding disease transmission dynamics and the potential role of maternal antibody transfer may help refine prevention measures. The objectives of this study were twofold: (i) understand the temporal and spatial disease transmission dynamics, and (ii) test the efficacy of vaccination in eliciting a specific immune response and protecting albatrosses against Pasteurella-induced mortality. Across the years 2013-5, blood samples were taken from several hundred Indian Yellow-Nosed Albatrosses on Amsterdam Island to assess serological response to pathogen exposure. A specifically designed vaccine was also used on adults and chicks, and tested for its effect on seroconversion and survival rates. Finally, 10 Subantarctic Skuas were equipped with GPS-UHF loggers and sampled to assess their potential role in disease dissemination. Serology suggested some natural pathogen circulation which varied between years, and showed that most birds responded to vaccination with an increase in antibody titres followed by a decline over time. Chick vaccination also proved effective the year when the epidemic was most severe. Finally, tracked skuas regularly visited albatross colonies, compatible with a role in disease circulation within and between albatross colonies. Vaccination could be a promising tool to protect these and neighbouring endangered albatross populations in the face of this emerging pathogen, and similar approaches could be applied to other settings. Further analyses are required to refine our understanding of disease transmission and possibly design more targeted prophylactic measures.
Programme: 1151
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Boulinier, T. (2016). Ecology and evolution of a transgenerational induced response, the maternal transfer of antibodies. Workshop Epigenetics in Ecology and Evolution, Labex CEMEB, Montpellier, 4 Avril..
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