Abstract: The 46 kDa xylanase from the Antarctic microorganism Pseudoalteromonas haloplanktis is an enzyme that efficiently catalyzes reactions at low temperatures. Here, the crystallization of both the native protein and the SeMet-substituted enzyme and data collection from both crystals using synchrotron radiation are described. The native data showed that the crystals diffract to 1.3 A resolution and belong to space group P212121, with unit-cell parameters a = 50.87, b = 90.51, c = 97.23 A. SAD data collected at the peak of the selenium absorption edge proved to be sufficient to determine the heavy-atom configuration and to obtain electron density of good quality.

Abstract: Niche variation is a widespread phenomenon that has important implications for ecological interactions and conservation biology, but few studies have quantified the trophic niche width (TNW) and its within- and between-individual components. We used stable isotopes of body feathers to investigate (1) seasonal isotopic niche changes of 4 southern procellariiforms and, (2) the level to which individuals are specialised relative to their population within each season. (1) δ13C and δ15N values of chicks and adults indicated a well-defined trophic segregation within the seabird assemblage during both the breeding and poorly known moulting (inter-nesting) periods, and they underlined marked species-specific seasonal changes. One species (light-mantled sooty albatross) remained within the Southern Ocean both during breeding and body feather moult, while the 3 others migrated either to oceanic subtropical waters (wandering and sooty albatrosses) or high isotopic marine areas (e.g. productive neritic waters; white-chinned petrel) during the moulting period. (2) Isotopic variances and TNW were generally low, indicating that birds belong to isotopic specialist populations within a given period. Variances and TNW were larger for white-chinned petrel chicks and light-mantled sooty albatross adults, respectively, indicating isotopic generalist populations and revealing 2 new foraging behaviours. Individual white-chinned petrel chicks segregated by their feather isotopic signatures, thus indicating individual/pair specialisation of parent birds during the chick-rearing period. The light-mantled sooty albatross population included mostly isotopic generalist individuals during the moulting period, with individuals using different habitats and diets. The study highlights the utility of feather isotopic signature for determining TNW and points out the necessity to develop such new approaches to better depict niche variations at both population and individual levels.

Abstract: Context. The recent measurement of linear polarization in the Earth thermospheric oxygen red line shows that it can be a useful observable quantity to characterise the upper atmospheres conditions. Therefore, polarimetry measurements are extended to other planets. Considering that FUV emissions are not observable from the ground, the best candidates for Jupiter auroral emissions are
H3+ infrared emissions around 4µm. This ion is created after a chemical process in the jovian upper atmosphere. Then, the anisotropy responsible of the polarization cannot be the particle impact as in the Earth case
Aims. The goal of this study is to detect some potential linear polarisation in the H3+ emissions of the jovian auroral oval.
Methods. Measurements of the H3+ emissions from the south auroral oval have been performed at the UKIRT during the beginning of August 2008, using the UIST-IRPOL spectro-polarimeter. The slit have been positioned perpendicularly to the jovian rotation axis.
Data were processed by dividing the slit in 24 bins. Stokes parameters u and q, polarization degree and direction are extracted for
each bin and debiased.
Results. Polarization up to 8% is detected. More than 7 bins show polarization with confidence level above 3σ. The better signal to noise ratio appears in the main auroral oval but no clear link appears between the polarization degrees and angles and the local known
anisotropies. The angles are a bit higher than 90° in the West part of the oval and mostly around 90° for the East part.
Conclusions. This study shows that polarization is detectable in the jovian infrared auroras. However, it is impossible to link it with electric or magnetic field for the moment due to the lack of theoretical work and laboratory experiments concerning the polarization of H3+.

Abstract: Physical and biological characteristics of benthic communities are analysed from underwater video footage collected across the George V Shelf during the 2007/2008 CEAMARC voyage. Benthic habitats are strongly structured by physical processes operating over a range of temporal and spatial scales. Iceberg scouring recurs over timescales of years to centuries along shallower parts of the shelf, creating communities in various stages of maturity and recolonisation. Upwelling of modified circumpolar deep water (MCDW) onto the outer shelf and cross-shelf flow of high-salinity shelf water (HSSW) create spatial contrasts in nutrient and sediment supply, which are largely reflected in the distribution of deposit- and filter-feeding communities. Long-term cycles in the advance and retreat of icesheets (over millennial scales) and subsequent focussing of sediments in troughs such as the Mertz Drift create patches of consolidated and soft sediments, which also provide distinct habitats for colonisation by different biota. These physical processes of iceberg scouring, current regimes and depositional environments, in addition to water depth, are important factors in the structure of benthic communities across the George V Shelf. The modern shelf communities mapped in this study largely represent colonisation over the past 8000-12,000 years, following retreat of the icesheet and glaciers at the end of the last glaciation. Recolonisation on this shelf may have occurred from two sources: deep-sea environments and possible shelf refugia on the Mertz and Adélie Banks. However, any open-shelf area would have been subject to intense iceberg scouring. Understanding the timescales over which shelf communities have evolved and the physical factors which shape them will allow better prediction of the distribution of Antarctic shelf communities and their vulnerability to change. This knowledge can aid better management regimes for the Antarctic margin.