. (2020). The metabolic cost of subcutaneous and abdominal rewarming in king penguins after long-term immersion in cold water (Vol. 91).
Keywords: Metabolism Normothermia Rewarming Subcutaneous temperature
Programme: 394
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. (2020). Plutonic processes in transitional oceanic plateau crust: Structure, age and emplacement of the South Rallier du Baty laccolith, Kerguelen Islands (Vol. 32). Bachelor's thesis, , .
Keywords: alkaline magmatism Kerguelen oceanic plateau pluton emplacement syenite intrusion
Programme: 444-1077
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Eveline Pinseel, Steven B. Janssens, Elie Verleyen, Pieter Vanormelingen, Tyler J. Kohler, Elisabeth M. Biersma, Koen Sabbe, Bart Van de Vijver, Wim Vyverman. (2020). Global radiation in a rare biosphere soil diatom (Vol. 11). Bachelor's thesis, , .
Abstract: Soil micro-organisms drive the global carbon and nutrient cycles that underlie essential ecosystem functions. Yet, we are only beginning to grasp the drivers of terrestrial microbial diversity and biogeography, which presents a substantial barrier to understanding community dynamics and ecosystem functioning. This is especially true for soil protists, which despite their functional significance have received comparatively less interest than their bacterial counterparts. Here, we investigate the diversification of Pinnularia borealis, a rare biosphere soil diatom species complex, using a global sampling of >800 strains. We document unprecedented high levels of species-diversity, reflecting a global radiation since the Eocene/Oligocene global cooling. Our analyses suggest diversification was largely driven by colonization of novel geographic areas and subsequent evolution in isolation. These results illuminate our understanding of how protist diversity, biogeographical patterns, and members of the rare biosphere are generated, and suggest allopatric speciation to be a powerful mechanism for diversification of micro-organisms.
Keywords: Biogeography Phylogenetics Speciation
Programme: 136,1167
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. (2020). A Micro-Mechanical Model for the Transformation of Dry Polar Firn Into Ice Using the Level-Set Method (Vol. 8).
Abstract: Interpretation of greenhouse gas records in polar ice cores requires a good understanding of the mechanisms controlling gas trapping in polar ice, and therefore of the processes of densification and pore closure in firn (compacted snow). Current firn densification models are based on a macroscopic description of the firn and rely on empirical laws and/or idealized geometries to obtain the equations governing the densification and pore closure. Here, we propose a physically-based methodology explicitly representing the porous structure and its evolution over time. In order to handle the complex geometry and topological changes that occur during firn densification, we rely on a Level-Set representation of the interface between the ice and the pores. Two mechanisms are considered for the displacement of the interface: (i) mass surface diffusion driven by local pore curvature and (ii) ice dislocation creep. For the latter, ice is modeled as a viscous material and the flow velocities are solutions of the Stokes equations. First applications show that the model is able to densify firn and split pores. Using the model in cold and arid conditions of the Antarctic plateau, we show that gas trapping models do not have to consider the reduced compressibility of closed pores compared to open pores in the deepest part of firns. Our results also suggest that the mechanism of curvature-driven surface diffusion does not result in pore splitting, and that ice creep has to be taken into account for pores to close. Future applications of this type of model could help quantify the evolution and closure of firn porous networks for various accumulation and temperature conditions.
Programme: 1153
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. (2020). (Vol. 109).
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Y. Quesnel, W. Zylberman, P. Rochette, M. Uehara, J. Gattacceca, G. R. Osinski, P. Dussouillez, C. Lepaulard, C. Champollion. (2020). Geophysical signature of the Tunnunik impact structure, Northwest Territories, Canada (Vol. 55).
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. (2020). Mass Spectrometry Imaging of Specialized Metabolites for Predicting Lichen Fitness and Snail Foraging (Vol. 9).
Abstract: Lichens are slow-growing organisms supposed to synthetize specialized metabolites to protect themselves against diverse grazers. As predicted by the optimal defense theory (ODT), lichens are expected to invest specialized metabolites in higher levels in reproductive tissues compared to thallus. We investigated whether Laser Desorption Ionization coupled to Mass Spectrometry Imaging (LDI-MSI) could be a relevant tool for chemical ecology issues such as ODT. In the present study, this method was applied to cross-sections of thalli and reproductive tissues of the lichen Pseudocyphellaria crocata. Spatial mapping revealed phenolic families of metabolites. A quantification of these metabolites was carried out in addition to spatial imaging. By this method, accumulation of specialized metabolites was observed in both reproductive parts (apothecia and soralia) of P. crocata, but their nature depended on the lichen organs: apothecia concentrated norstictic acid, tenuiorin, and pulvinic acid derivatives, whereas soralia mainly contained tenuiorin and pulvinic acid. Stictic acid, tenuiorin and calycin, tested in no-choices feeding experiments, were deterrent for N. hookeri while entire thalli were consumed by the snail. To improve better knowledge in relationships between grazed and grazing organisms, LDI-MSI appears to be a complementary tool in ecological studies
Keywords: Notodiscus hookeri Pseudocyphellaria crocata Chemical Ecology Lichens Lobariaceae Mass Spectrometry Imaging Optimal Defense Theory Specialized Metabolites
Programme: 136
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. (2020). Enhanced upward heat transport at deep submesoscale ocean fronts (Vol. 13). Bachelor's thesis, , .
Keywords: Physical oceanography
Programme: 109,1201
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Jan Jansen, Piers K. Dunstan, Nicole A. Hill, Philippe Koubbi, Jessica Melbourne-Thomas, Romain Causse, Craig R. Johnson. (2020). Integrated assessment of the spatial distribution and structural dynamics of deep benthic marine communities (Vol. 30).
Abstract: Characterizing the spatial distribution and variation of species communities and validating these characteristics with data from the field are key elements for an ecosystem-based approach to management. However, models of species distributions that yield community structure are usually not linked to models of community dynamics, constraining understanding and management of the ecosystem, particularly in data-poor regions. Here we use a qualitative network model to predict changes in Antarctic benthic community structure between major marine habitats characterized largely by seafloor depth and slope, and use multivariate mixture models of species distributions to validate the community dynamics. We then assess how future increases in primary production associated with anticipated loss of sea-ice may affect the ecosystem. Our study shows how both spatial and structural features of ecosystems in data-poor regions can be analyzed and possible futures assessed, with direct relevance for ecosystem-based management.
Keywords: Antarctica continental shelf deep sea ecosystem dynamic ecosystem structure qualitative network model Southern Ocean spatial model species archetype model upper slope
Programme: 281
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Renac Christophe, Moine Bertrand, Goudour Jean-Pierre, LeRomancer Marc, Perrache Chantal. (2020). Stable isotope study of rainfall, river drainage and hot springs of the kerguelen archipelago, SW Indian Ocean (Vol. 83). Bachelor's thesis, , .
Keywords: Geothermal springs Kerguelen archipelago Stable isotope composition Water-Rock interaction
Programme: 408,444
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