Abstract: Unesco Int.Academic Conference. Ten years after the Chernobyl Catastrophe. Minsk, Belarus

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.

Abstract: Understanding the regulation of natural populations has been a long-standing research program in ecology. Current knowledge on marine mammals and seabirds is biased toward the adult component of populations and lacking are studies investigating the juvenile component. Our goal was to estimate demographic parameters on the pre-weaning stage of a subantarctic fur seal (Arctocephalus tropicalis) population on Amsterdam Island, suspected to be regulated by density-dependence. The influence of abundance on growth parameters (length and weight) and survival was assessed over a study period spanning 16 years. We evidenced a negative trend in population growth rate when density increased. Density-dependence models were favored for pup body size and mass growth. Abundance had a clear influence on body length at high population-density, pups grew slower and were smaller at weaning than pups born in years with low population density. Abundance partly explained pup body mass variation and a weak effect was detected on pre-weaning survival. The causal mechanisms may be increased competition for food resources between breeding females, leading to a reduction of maternal input to their pups. Our results suggested that pup favored survival over growth and the development of their diving abilities in order to withstand the extreme fasting periods that are characteristic of this fur seal population. This analysis provides significant insight of density-dependent processes on early-life demographic parameters of a long lived and top-predator species, and more specifically on the pre-weaning stage with important consequences for our understanding of individual long-term fitness and population dynamics.

Abstract: Understanding the processes structuring communities is a fundamental goal in ecology and conservation biology. Seabirds are commonly used as sentinels of marine ecosystems, but there is a lack of quantitative information providing a synoptic view of their community structure and of its underlying mechanisms. We used stable isotope analysis of chick feathers to investigate the structure of 2 communities that are representative of the subantarctic (Kerguelen) and Antarctic (Adélie Land) seabird diversity. Total area of the convex hull (a measure of the total δ13C-δ15N niche space) was 8.4-fold higher at the Kerguelen Islands than in Adélie Land, a consequence of the higher seabird diversity at the former locality. Kerguelen seabirds grouped into 2 clusters of oceanic and inshore species, with the latter group not represented in Adélie Land. Communities are primarily structured by the availability of foraging habitats (δ13C) and then of trophic resources (δ15N), with body size being a major driving force of trophic position. Ecological characteristics are more important than phylogeny to shape seabird isotopic niche breadth (standard ellipse area corrected for small sample size, SEAc), with no significant differences between Sphenisciformes, Procellariiformes, and Charadriiformes. By contrast, SEAc varies according to foraging guilds, diet, and a specialist-generalist gradient, with ubiquitous seabirds having a 10-fold larger mean SEAc than pelagic divers. This study sets a baseline against which the effects of long-term environmental changes on seabird community structure can be studied across years and conditions, and provides a relevant starting point for the investigation into the effect of climate change on Southern Ocean ecosystems.

Abstract: Understanding the meteorological drivers of precipitation isotopic composition is crucial for the
interpretation of paleoclimate archives, such as the past precipitation records found in the ice
cores, as well as to successfully constrain atmospheric models including the explicit
representation of water isotopes. This is of particular importance in the context of climate change,
and in particular in the Arctic where climate models project enhanced hydrological cycle and
temperature increase which might in turn have significant impacts on the global climate (through
e.g. the sea-ice retreat, water vapour feedback or cloud cover). Indeed, large discrepancies on the
future Arctic precipitation exist amongst different climate models.
Condensing water vapour being the first stage of a precipitation event, its isotopic composition
influences that of the precipitation and must therefore be fully understood in order to find the
causes for the inter-model spread. The water vapour isotopic composition is believed to be
influenced by changes in moisture sources and fractionation history during transport. It thus
provides valuable and independent information on moisture source origins and represents a
crucial tool for assessing the realism of models and the interpretation of meteorological archives.
During the last 5 years, new laser methods have permitted to achieve such measurements of water
isotopes.
In the present work, new in situ continuous measurements of the isotopic composition of water
vapour in Svalbard between the end of June 2014 and March 2015 are studied. Given its location,
Svalbard allowed us to expand the monitoring of water vapour isotopic composition and
atmospheric circulation towards the Arctic so as to explore their relationship to the moisture
source conditions. In order to do so, Lagrangian backtrajectories were computed and associated
with the processed data.
A clear distinction between trajectories coming from over the Arctic sea-ice area and those from
the North Atlantic Ocean could be observed in the isotopic composition. The latter also displayed
seasonal variations attributed to seasonal changes in atmospheric transport. Moreover, during
days with low isotopic depletion, deviations from the expected global meteoric water line were
observed and studied. Finally, days displaying a significant and rapid change in the isotopic
composition were explained by a corresponding sudden change in the air mass past trajectory.
This work opens the possibility to quantify the effects of evaporation conditions on isotopic data,
provides a new dataset for the evaluation of atmospheric models, and will provide a basis to
revise the climatic interpretation of Svalbard ice core records.