Abstract: High southern latitude regions present specificities that are highly relevant for studying the climate in connection with the atmospheric chemistry. Contrary to regions of the rest of the world, Antarctica is still considered as a pristine environment not yet influenced by predominant anthropogenic emissions (with the notable exceptions of GHG) and thus represents the last continental-size natural laboratory. Polar snow-air-radiation interactions and the specific oxidant character of the polar atmosphere are key in order to decipher the right information buried in the ice and the current chemical stability of the polar atmosphere. Previous Antarctic campaigns have shown atmospheric similarities between the Antarctic Plateau (at Dome C, Concordia) and other regions. However, several differences are yet to be explained: the large NO2:NO ratios previously found in ambient air indicates the existence of an unknown source of NO2 above the Antarctic Plateau. These observations question either the reliability of previous measurements or the lack of our understanding of the NOx chemistry. Novel optical instruments based on the incoherent broadband cavity enhanced absorption spectroscopy technique (IBBCEAS) were developed. The instruments can measure simultaneously NO2, NOx and NO with detection limits of 11, 10 and 21 ppt, respectively (1σ) within 22 minutes of measurements. The two compact and transportable instruments were deployed during the 2019/20 Dome C summer campaign. Atmospheric measurements together with flux chamber experiments were performed for determining the snowpack NOx emissions and the NO2:NO ratio. The observations seem to differ from the conclusions of the previous Antarctic campaigns. Assuming steady state and maximum radiations, the theoretical NO2:NO ratio from the period observed in December was calculated to be 0.38 ± 0.15 and 0.31 ± 0.12 in January. The instruments measured a ratio close to steady state in December (0.25 ± 0.25) while the ratio observed in January (1.248 ± 0.792) indicates the presence of a strong NO oxidant or an unknown source of NO2. Flux chamber experiments on different types of snow were done during this campaign, and the results will help deepen our knowledge of Antarctic atmospheric chemistry.

Abstract: Kerguelen Islands harbor a unique, probably very ancient flora with a high rate of endemism. However, the evolutionary history and characteristics of this flora still require investigation. This concerns in particular genome size and ploidy level variation, despite the evolutionary and ecological significance of those traits. Here we report the first assessment of genome size, using flow cytometry, for eight plant species of which two are endemics of Kerguelen Islands and four of the South Indian Ocean Province. The 2C DNA value ranged from 1.08 pg for Pringlea antiscorbutica to 11.88 pg for Ranunculus biternatus. The chromosome numbers of Colobanthus kerguelensis (2n = 80), Lyallia kerguelensis (2n = 96) and Poa kerguelensis (2n = 28) were also reported in this study for the first time. Overall, our data allowed to infer that all Kerguelen studied species are polyploid (from tetra- to octopolyploid). Intra-genus comparisons showed significant differences of 2C DNA values among Poa and among Ranunculus species, despite their identical ploidy level. In addition, our data highlight the existence of an intraspecific variability of genome size for the two octoploid species Colobanthus kerguelensis and Lyallia kerguelensis. Finally, our data also support the hypothesis regarding which polyploidy may have played a major role in the adaptation of flowering plants to high latitudes, as it has been suggested for arctic species.