Christophe Barbraud, Karine Delord, Charles A. Bost, Adrien Chaigne, Cédric Marteau, Henri Weimerskirch. (2020). Population trends of penguins in the French Southern Territories (Vol. 43). Bachelor's thesis, , .
Abstract: Penguins are important top consumers in marine food webs and are one of the most threatened bird families, especially by climate change and food web alterations by marine fisheries. Yet, long-term population trends are lacking or are uncertain for many populations. Seven species of penguins breeding at the French Southern Territories in the southern Indian Ocean on the Crozet, Kerguelen, Saint-Paul–Amsterdam archipelagos and in Terre Adélie/Adelie Land, Antarctica are monitored regularly. This monitoring started in the early 1950s and most populations have been surveyed during the past four years, allowing assessments of population trends. King penguins increased at nearly all breeding sites within the Crozet and Kerguelen archipelagos. Emperor penguins have decreased at Terre Adélie/Adelie Land, with a partial recovery of the colony during the 2010s. Gentoo penguin populations at Crozet and Kerguelen are highly variable but stable. Adélie penguins have been increasing in Terre Adélie/Adelie Land. The trends in eastern rockhopper penguins vary between colonies and archipelagos. Northern rockhopper penguins have continuously decreased in numbers at Amsterdam Island, but appear to have increased at the nearby Saint-Paul Island. Macaroni penguins have first increased and then stabilized since the 2000s at Kerguelen and are stable at the Crozet Islands. Overall, most penguin populations breeding in the French Southern Territories increased or were stable over the past 30–60 years, with the exception of the northern rockhopper penguin, king and gentoo penguins on Crozet and the emperor penguin. The ecological reasons for these trends are poorly understood and require further investigation.
Programme: 109,394
|
Philippe Ricaud, Massimo Del Guasta, Eric Bazile, Niramson Azouz, Angelo Lupi, Pierre Durand, Jean-Luc Attié, Dana Veron, Vincent Guidard, Paolo Grigioni. (2020). Supercooled liquid water cloud observed, analysed, and modelled at the top of the planetary boundary layer above Dome C, Antarctica (Vol. 20).
Abstract: Abstract. A comprehensive analysis of the water budget over the Dome C (Concordia, Antarctica) station has been performed during the austral summer 2018–2019 as part of the Year of Polar Prediction (YOPP) international campaign. Thin (∼100 m deep) supercooled liquid water (SLW) clouds have been detected and analysed using remotely sensed observations at the station (tropospheric depolarization lidar, the H2O Antarctica Microwave Stratospheric and Tropospheric Radiometer (HAMSTRAD), net surface radiation from the Baseline Surface Radiation Network (BSRN)), radiosondes, and satellite observations (CALIOP, Cloud-Aerosol LIdar with Orthogonal Polarization/CALIPSO, Cloud Aerosol Lidar and Infrared Pathfinder Satellite Observations) combined with a specific configuration of the numerical weather prediction model: ARPEGE-SH (Action de Recherche Petite Echelle Grande Echelle – Southern Hemisphere). The analysis shows that SLW clouds were present from November to March, with the greatest frequency occurring in December and January when ∼50 % of the days in summer time exhibited SLW clouds for at least 1 h. Two case studies are used to illustrate this phenomenon. On 24 December 2018, the atmospheric planetary boundary layer (PBL) evolved following a typical diurnal variation, which is to say with a warm and dry mixing layer at local noon thicker than the cold and dry stable layer at local midnight. Our study showed that the SLW clouds were observed at Dome C within the entrainment and the capping inversion zones at the top of the PBL. ARPEGE-SH was not able to correctly estimate the ratio between liquid and solid water inside the clouds with the liquid water path (LWP) strongly underestimated by a factor of 1000 compared to observations. The lack of simulated SLW in the model impacted the net surface radiation that was 20–30 W m−2 higher in the BSRN observations than in the ARPEGE-SH calculations, mainly attributable to the BSRN longwave downward surface radiation being 50 W m−2 greater than that of ARPEGE-SH. The second case study took place on 20 December 2018, when a warm and wet episode impacted the PBL with no clear diurnal cycle of the PBL top. SLW cloud appearance within the entrainment and capping inversion zones coincided with the warm and wet event. The amount of liquid water measured by HAMSTRAD was ∼20 times greater in this perturbed PBL than in the typical PBL. Since ARPEGE-SH was not able to accurately reproduce these SLW clouds, the discrepancy between the observed and calculated net surface radiation was even greater than in the typical PBL case, reaching +50 W m−2, mainly attributable to the downwelling longwave surface radiation from BSRN being 100 W m−2 greater than that of ARPEGE-SH. The model was then run with a new partition function favouring liquid water for temperatures below −20 down to −40 ∘C. In this test mode, ARPEGE-SH has been able to generate SLW clouds with modelled LWP and net surface radiation consistent with observations during the typical case, whereas, during the perturbed case, the modelled LWP was 10 times less than the observations and the modelled net surface radiation remained lower than the observations by ∼50 W m−2. Accurately modelling the presence of SLW clouds appears crucial to correctly simulate the surface energy budget over the Antarctic Plateau.
Programme: 910
|
Jean Lilensten, Mathieu Barthélemy, Gérard Besson, Hervé Lamy, Magnar G. Johnsen, Jøran Moen. (2016). The thermospheric auroral red line Angle of Linear Polarization (Vol. 121).
Abstract: The auroral red line at 630 nm is linearly polarized. Up to now, only its Degree of Linear Polarization had been studied. In this article, we examine for the first time the Angle of Linear Polarization (AoLP) and we compare the measurements to the apparent angle of the magnetic field at the location of the red line emission. We show that the AoLP is a tracer of the magnetic field configuration. This opens new perspectives, both in the frame of space weather and in the field of planetology.
Keywords: ionosphere polarization
Programme: 1026
|
B. Lauer, R. Grandin, Y. Klinger. (2020). Fault Geometry and Slip Distribution of the 2013 Mw 7.7 Balochistan Earthquake From Inversions of SAR and Optical Data (Vol. 125).
Abstract: The 2013 Mw 7.7 Balochistan earthquake ruptured the Hoshab fault (Pakistan) over 200 km. It was dominated by left-lateral slip, with a secondary reverse component. By combining optical (SPOT 5 and Landsat 8) and radar satellite data (RADARSAT-2 and TerraSAR-X ScanSAR), we derive the 3-D coseismic displacement field and the slip distribution. Our modeling strategy involves two successive inversions allowing to explore first the fault geometry and then slip distribution. Following a statistical analysis of the coseismic surface trace, the fault is discretized into 16 segments. To determine the dip angle and down-dip width of the segments, we then perform a non-linear elastic inversion of the geodetic data set. Using output of this model, we prescribe the fault geometry and linearly invert for slip at depth with refined discretization. Results show a decrease of the fault dip, reaching 50° in the central part of the fault that structurally connects the two sub-vertical terminations dipping at >70°. The distribution of strike-slip forms a shallow continuous patch (0–8 km) that peaks at 12.7 m of slip near the epicenter. Reverse slip is distributed on several patches and becomes shallower near the southern termination, where it peaks at 5.7 m. Our model shows an absence of shallow slip deficit (SSD), as for other Mw 7.5 + strike-slip earthquakes elsewhere, hence suggesting that SSD is only found for lesser magnitude earthquakes. We speculate that moment magnitude is a key element in the occurrence of SSD.
Keywords: Balochistan earthquake earthquake rupture modeling earthquake source processes InSAR optical data shallow slip deficit
Programme: 133
|
David T. Iles, Heather Lynch, Rubao Ji, Christophe Barbraud, Karine Delord, Stephanie Jenouvrier. (2020). Sea ice predicts long-term trends in Adélie penguin population growth, but not annual fluctuations: Results from a range-wide multiscale analysis (Vol. 26).
Abstract: Understanding the scales at which environmental variability affects populations is critical for projecting population dynamics and species distributions in rapidly changing environments. Here we used a multilevel Bayesian analysis of range-wide survey data for Adélie penguins to characterize multidecadal and annual effects of sea ice on population growth. We found that mean sea ice concentration at breeding colonies (i.e., “prevailing” environmental conditions) had robust nonlinear effects on multidecadal population trends and explained over 85% of the variance in mean population growth rates among sites. In contrast, despite considerable year-to-year fluctuations in abundance at most breeding colonies, annual sea ice fluctuations often explained less than 10% of the temporal variance in population growth rates. Our study provides an understanding of the spatially and temporally dynamic environmental factors that define the range limits of Adélie penguins, further establishing this iconic marine predator as a true sea ice obligate and providing a firm basis for projection under scenarios of future climate change. Yet, given the weak effects of annual sea ice relative to the large unexplained variance in year-to-year growth rates, the ability to generate useful short-term forecasts of Adélie penguin breeding abundance will be extremely limited. Our approach provides a powerful framework for linking short- and longer term population processes to environmental conditions that can be applied to any species, facilitating a richer understanding of ecological predictability and sensitivity to global change.
Keywords: Antarctica environmental variation habitat suitability niche predictability state-space stochastic uncertainty
Programme: 109
|
D. B. Green, S. Bestley, R. Trebilco, S. P. Corney, P. Lehodey, C. R. McMahon, C. Guinet, Mark A. Hindell. (2020). Modelled mid-trophic pelagic prey fields improve understanding of marine predator foraging behaviour (Vol. 43). Bachelor's thesis, , .
Abstract: Biophysical interactions are influential in determining the scale of key ecological processes within marine ecosystems. For oceanic predators, this means foraging behaviour is influenced by processes shaping the distribution of prey. However, oceanic prey is difficult to observe and its abundance and distribution is regionally generalised. We use a spatiotemporally resolved simulation model to describe mid-trophic prey distribution within the Southern Ocean and demonstrate insights that this modelled prey field provides into the foraging behaviour of a widely distributed marine predator, the southern elephant seal. From a five-year simulation of prey biomass, we computed climatologies of mean prey biomass (average prey conditions) and prey biomass variability (meso-scale variability). We also compiled spatially gridded metrics of seal density and diving behaviour from 13 yr of tracking data. We statistically modelled these metrics as non-linear functions of prey biomass (both mean and variability) and used these to predict seal distribution and behaviour. Our predictions were consistent with observations (R2adj = 0.23), indicating that seals aggregate in regions of high mesoscale activity where eddies concentrate prey. Here, seals dived deeper (R2marg = 0.12, R2cond = 0.51) and spent less time hunting (R2marg = 0.05, R2cond = 0.56), likely targeting deep but profitable prey patches. Seals generally avoided areas of low eddy activity where prey was likely dispersed. Most seals foraged south of the Subantarctic Front, despite north of the front exhibiting consistently high simulated prey biomasses. This likely reflects seal prey or habitat preferences, but also emphasises the importance of mesoscale prey biomass variability relative to regionally high mean biomass. This work demonstrates the value of coupling mechanistic representations of prey biomass with predator observations to provide insight into how biophysical processes combine to shape species distributions. This will be increasingly important for the robust prediction of species’ responses to rapid system change.
Keywords: ecosystem modelling kerguelen plateau micronekton predators prey interaction southern elephant seal Southern Indian Ocean
Programme: 109,1201
|
Emmanuelle Barreau, Yan Ropert-Coudert, Karine Delord, Christophe Barbraud, Akiko Kato-Ropert. (2019). Scale matters: sea ice and breeding success of Adélie penguins (Vol. 42). Bachelor's thesis, , .
Abstract: Southern Ocean ecosystems are extremely vulnerable to sea-ice changes occurring at different spatial and temporal scales. Variability in the sea-ice conditions strongly influence the survival and reproduction of animals that are synchronized with the seasonality of sea ice. Although the linkages between Adélie penguins (Pygoscelis adeliae) and sea-ice conditions are well established, the spatial and temporal scales at which sea ice affects individuals and populations are poorly known. Using 23 years of penguin breeding success and remote-sensing data of sea ice, we investigate the spatial and temporal scales at which sea-ice changes best explain variations in the reproductive success of Adélie penguins at Pointe Géologie, East Antarctica. The best spatial scale encompassed all foraging areas exploited and all the sea-ice conditions encountered by penguins over a breeding season. There was a consistent influence of sea-ice concentration during the guard stage on the overall breeding success. We demonstrate the importance of considering sea ice at a fine temporal scale rather than using an average value over the breeding season to best explain reproductive success in Adélie penguins.
Programme: 109,1091
|
Bastien Labarrere, Andreas Prinzing, Thomas Dorey, Emeline Chesneau, Françoise Hennion. (2019). Variations of Secondary Metabolites among Natural Populations of Sub-Antarctic Ranunculus Species Suggest Functional Redundancy and Versatility (Vol. 8). Bachelor's thesis, , .
Abstract: Plants produce a high diversity of metabolites which help them sustain environmental stresses and are involved in local adaptation. However, shaped by both the genome and the environment, the patterns of variation of the metabolome in nature are difficult to decipher. Few studies have explored the relative parts of geographical region versus environment or phenotype in metabolomic variability within species and none have discussed a possible effect of the region on the correlations between metabolites and environments or phenotypes. In three sub-Antarctic Ranunculus species, we examined the role of region in metabolite differences and in the relationship between individual compounds and environmental conditions or phenotypic traits. Populations of three Ranunculus species were sampled across similar environmental gradients in two distinct geographical regions in îles Kerguelen. Two metabolite classes were studied, amines (quantified by high-performance liquid chromatography and fluorescence spectrophotometry) and flavonols (quantified by ultra-high-performance liquid chromatography with triple quadrupole mass spectrometry). Depending on regions, the same environment or the same trait may be related to different metabolites, suggesting metabolite redundancy within species. In several cases, a given metabolite showed different or even opposite relations with the same environmental condition or the same trait across the two regions, suggesting metabolite versatility within species. Our results suggest that metabolites may be functionally redundant and versatile within species, both in their response to environments and in their relation with the phenotype. These findings open new perspectives for understanding evolutionary responses of plants to environmental changes.
Keywords: Ranunculus biternatus Ranunculus moseleyi Ranunculus pseudotrullifolius amines environment natural populations quercetins redundancy secondary metabolite variation sub-Antarctic plants
Programme: 136,1116
|
Simon Véron, Carlos Rodrigues-Vaz, Elise Lebreton, Claudine Ah-Peng, Vincent Boullet, Hervé Chevillotte, Stephan Robbert Gradstein, Joël Jérémie, Elisabeth Lavocat Bernard, Marc Lebouvier, Jean-Yves Meyer, Jérôme Munzinger, Odile Poncy, Louis Thouvenot, Guillaume Viscardi, Guillaume Léotard, Olivier Gargominy, Sébastien Leblond, Marc Pignal, Germinal Rouhan, Sandrine Tercerie, Vanessa Invernon, Serge Muller. (2021). An assessment of the endemic spermatophytes, pteridophytes and bryophytes of the French Overseas Territories: towards a better conservation outlook (Vol. 30).
Abstract: A broad range of climatic and biogeographical conditions are represented in the French Overseas Territories, from sub-polar to equatorial, resulting in a high diversity of endemic species. We mobilized data from herbaria, floras, checklists, literature, the expertise of botanists and plant ecologists to compile the most complete dataset on endemic vascular plants and bryophytes in the 15 French Overseas Territories. To date, 3748 spermatophytes (seed plants), 244 pteridophytes (ferns and lycophytes) and 448 bryophytes are strictly endemic to the overseas territories. New Caledonia, French Polynesia and Réunion harbour the highest numbers of strictly endemic species, yet French Guiana and the French Antilles harbour high numbers of regional endemic species due to their proximity with other territories. The endemic flora of these territories is highly threatened. In particular, 51% of strictly endemic spermatophytes are threatened and many species at risk belong to Rubiaceae and Orchidaceae families. Around 82% and 69% of strict and regional endemic spermatophytes and pteridophytes are found in the Paris herbaria. Only 34% of endemic bryophytes have their label information fully databased so that their total number in Paris herbaria is not known. Databasing the remaining specimens in the collection will greatly enhance future research and conservation projects. To facilitate the use of the information we compiled, we provide a publicly searchable dataset of the checklist. This study not only provides a picture of the flora of French overseas territories; it also identifies gaps in knowledge on which future research efforts in systematics, ecology and conservation could focus.
Programme: 136
|
T. Guillot, L. Abe, A. Agabi, J.-P. Rivet, J.-B. Daban, D. Mékarnia, E. Aristidi, F.-X. Schmider, N. Crouzet, I. Gonçalves, C. Gouvret, S. Ottogalli, H. Faradji, P.-E. Blanc, E. Bondoux, F. Valbousquet. (2015). Thermalizing a telescope in Antarctica – analysis of ASTEP observations (Vol. 336).
Abstract: The installation and operation of a telescope in Antarctica represent particular challenges, in particular the requirement to operate at extremely cold temperatures, to cope with rapid temperature fluctuations and to prevent frosting. Heating of electronic subsystems is a necessity, but solutions must be found to avoid the turbulence induced by temperature fluctuations on the optical paths. ASTEP 400 is a 40cm Newton telescope installed at the Concordia station, Dome C since 2010 for photometric observations of fields of stars and their exoplanets. While the telescope is designed to spread star light on several pixels to maximize photometric stability, we show that it is nonetheless sensitive to the extreme variations of the seeing at the ground level (between about 0′′.1 and 5′′) and to temperature fluctuations between –30°C and –80 °C. We analyze both day-time and night-time observations and obtain the magnitude of the seeing caused by the mirrors, dome and camera. The most important effect arises from the heating of the primary mirror which gives rise to a mirror seeing of 0′′.23 K–1. We propose solutions to mitigate these effects. (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Keywords: instrumentation: photometers techniques: photometric telescopes
Programme: 1066
|