Abstract: The demography and factors affecting the population dynamics of gadfly petrels (Pterodroma spp.) remain poorly known, although they constitute the most diverse genus of Procellariiformes and many species are threaten. Using a long-term individual monitoring dataset over 35 years, this study provides estimates of state-specific demographic parameters of the White-headed Petrel (Pterodroma lessonii) from Mayes Island, Kerguelen archipelago, and tests for the effects of environmental factors. Age at first breeding was 8.7 ± 2.6 years and apparent adult annual survival was 0.941 ± 0.058. Annual breeding probability was 0.356 ± 0.036 for successful breeders and 0.988 ± 0.054 for individuals that took a sabbatical year after a successful breeding event. Successful breeders that bred during two consecutive years had a lower breeding success (0.574 ± 0.048) that individuals that bred after a sabbatical year (0.655 ± 0.036). The realized population growth rate (1.073 ± 0.011) suggested that the population is increasing. There was a slight evidence for a positive effect of the Southern Annular Mode on the breeding probability of successful breeders, but no effect of sea surface temperature, chlorophyll a or wind was detected on demographic parameters. This study revealed that White-headed Petrels had a particularly high adult survival coherent with a quasi-biennial strategy and late age at first breeding. According to life history theory, populations of White-headed Petrel are thus likely to be very sensitive to small variations in adult survival, and anthropogenic factors causing additive mortality such as introduced predators will constitute serious threats for this species.

Abstract: In a context of global warming and sea level rise acceleration, it is key to estimate the evolution of the atmospheric hydrological cycle and temperature in polar regions, which directly influence the surface mass balance of the Arctic and Antarctic ice sheets. Direct observations are available from satellite data for the last 40 years and a few weather data since the 1950s in Antarctica. One of the best ways to access longer records is to use climate proxies in firn or ice cores. The water isotopic composition in these cores is widely used to reconstruct past temperature variations. We need to progress in our understanding of the influence of the atmospheric hydrological cycle on the water isotopic composition of ice cores. First, we present a 2-year-long time series of vapor and precipitation isotopic composition measurement at Dumont d’Urville Station, in Adélie Land. We characterize diurnal variations of meteorological parameters (temperature, atmospheric water mixing ratio (hereafter humidity) and δ18O) for the different seasons and determine the evolution of key relationships (δ18O versus temperature or humidity) throughout the year: we find that the temperature vs. δ18O relationship is dependent on synoptic events dynamics in winter contrary to summer. Then, this data set is used to evaluate the atmospheric general circulation model ECHAM6-wiso (model version with embedded water stable isotopes) in a coastal region of Adélie Land where local conditions are controlled by strong katabatic winds which directly impact the isotopic signal. We show that a combination of continental (79 %) and oceanic (21 %) grid cells leads model outputs (temperature, humidity and δ18O) to nicely fit the observations, at different timescales (i.e., seasonal to synoptic). Therefore we demonstrate the added value of long-term water vapor isotopic composition records for model evaluation. Then, as a clear link is found between the isotopic composition of water vapor and precipitation, we assess how isotopic models can help interpret short firn cores. In fact, a virtual firn core built from ECHAM-wiso outputs explains much more of the variability observed in S1C1 isotopic record than a virtual firn core built from temperature only. Yet, deposition and post-deposition effects strongly affect the firn isotopic signal and probably account for most of the remaining misfits between archived firn signal and virtual firn core based on atmospheric modeling.

Abstract: Reliably recording very low ambient concentrations of gaseous elemental mercury (GEM) in remote regions is often required, for example in the context of evaluating how effective the Minamata Convention is in reducing global Hg emissions. However, sampling over extended periods of time at sites that are difficult to access can be very challenging. In order to establish what role inexpensive and easy-to-use passive air samplers may play in this regard, we deployed a sampler using a Radiello diffusive barrier and activated carbon sorbent for periods of up to three years and with sampling periods ranging from one to three months in some of the most extreme, remote and challenging global environments: at Concordia station on the Antarctic plateau, on Amsterdam Island in the remote Southern Indian Ocean and at several sites on the tropical island of La Réunion. The ability to reliably record the GEM concentrations at these sites was strongly influenced by the size of the sequestered amount of mercury relative to the extent and variability of the contamination of field blank samples. In some cases, acceptably low and consistent field blank contamination could only be achieved by storing samplers in sealed glass jars during transport and storage. The size of the sequestered amount is easily increased by extending deployment times, and the experience of the current study suggests that deployment periods in excess of two months are advisable. Sampling in Antarctica was compromised by the extreme low temperatures, which caused unknown sampling rates, hoar frost accumulation, material failure and potential failure of storage seals. While good agreement with GEM concentrations measured with an active sampler was noted on Amsterdam Island, the passive sampler derived levels at the Maïdo Observatory in La Réunion were notably higher than concentrations measured simultaneously with a Tekran vapour analyzer, which was possibly related to sampling rates being temporarily elevated at the very beginning of deployment at low GEM concentrations.

Abstract: Poor coverage of the Antarctic continental shelf bathymetry impedes understanding the oceanographic processes affecting Antarctica’s role in global climate. Continental shelf bathymetry influences warm modified Circumpolar Deep Water movement onto the shelf, making it an important factor promoting ice shelf melting and influencing the flow of ice shelves into the ocean. Building on previous work using seal dives to redefine bathymetry, our longitudinal study of ocean physics and animal behaviour provided new depth information from over 500,000 individual seal dives on the East Antarctic continental shelf. About 25% of these seal dives were 220 m (sometimes over 1000 m) deeper than the interpolated seafloor from IBCSO V2. Focusing on four well-sampled regions, we show that the bathymetry of 22% to 60% of the sampled area was improved by incorporating seal dive data. This revealed new bathymetric features, including troughs off the Shackleton Ice Shelf and Underwood Glacier and a deep canyon near the Vanderford Glacier. This deep canyon, the Mirounga-Nuyina Canyon, was confirmed by a recent multi-beam echo sounder survey. Further acquisitions of seal data will improve our understanding and modelling of Antarctic coastal ocean processes and ice-sheet dynamics.

Abstract: In Antarctica, there is growing concern about the potential effect of anthropogenic activities (i.e., tourism, research) on wildlife, especially since human activities are developing at an unprecedented rate. Although guidelines exist to mitigate negative impacts, fundamental data are currently lacking to reliably assess impacts. Physiological tools, such as circulating corticosterone levels, appear promising to assess the potential impact of human disturbance on Antarctic vertebrates. In this study, we compared the body condition, and the physiological sensitivity to stress (i.e., basal and stress-induced corticosterone level) of adult and chick Adélie penguins between a disturbed and an undisturbed area (i.e., 2 colonies located in the middle of a research station exposed to intense human activities and 2 colonies located on protected islands with minimal human disturbance). We did not find any significant impact of human activities on body condition and corticosterone levels in adults (incubating adults, brooding adults). In chicks, there were significant inter-colony variations in stress-induced corticosterone levels. Specifically, the chicks from the disturbed colonies tended to have higher stress-induced corticosterone levels than the chicks from the protected areas although this difference between areas was not significant. Overall, our study suggests that this species is not dramatically impacted by human activities, at least when humans and penguins have cohabited for several decades. Our results support therefore the idea that this species is likely to be tolerant to human disturbance and this corroborates with the persistence of Adélie penguin colonies in the middle of the research station. However, our results also suggest that chicks might be more sensitive to human disturbance than adults and might therefore potentially suffer from human disturbance. In addition, and independently of human disturbance we also found significant differences in adult body condition, and chick corticosterone level between colonies, suggesting that other individual and environmental variables outweigh the potential minor impact of human disturbance on these variables. Combining corticosterone with complementary stress-related physiological markers, such as heart rate, may strengthen further studies examining whether human disturbance may have subtle detrimental impacts on individuals.