Abstract: The 2016 Kaikoura earthquake, New Zealand, ruptured more than a dozen faults, making it difficult to prescribe a model fault for analyzing the event by inversion. To model this earthquake from teleseismic records, we used a potency density tensor inversion, which projects multiple fault slips onto a single model fault plane, reducing the non-uniqueness due to the uncertainty in selecting the faults’ orientations. The resulting distribution of potency-rate density tensors is consistent with observed surface ruptures. In its initial stage, the rupture propagated northeastward primarily at shallow depths. Later, the rupture propagated northeastward at greater depths beneath a gap in reported surface ruptures. The main rupture phase started in the northeastern part of the Kekerengu fault after 50 s and propagated bilaterally to the northeast and southwest. The non-double-couple component grew to a large fraction of the source elements as the rupture went through the junction of the Jordan Thrust and the Papatea fault, which suggests that the rupture branched into both faults as it back-propagated toward the southwest. The potency density tensor inversion sheds new light on the irregular evolution of this earthquake, which produced a fault rupture pattern of unprecedented complexity. Our source model of the 2016 Kaikoura earthquake (e.g., back-rupture propagation) could prompt research to determine a more realistic model with segmented faults using near-field data.

Abstract: Animals have to develop novel behaviours to adapt to anthropogenic activities or environmental changes. Fishing vessels constitute a recent feature that attracts albatrosses in large numbers. While they provide a valuable food source through offal and bait, they cause mortalities through bycatch, such that selection on vessel attraction will depend on the cost–benefit balance. We examine whether attraction to fishing and other vessels changes through the lifetime of great albatrosses, and show that attraction differed between age classes, sexes and personality. Juveniles encountered fewer vessels than adults, but also showed a lower attraction to vessels when encountered. Attraction rates, especially for fishing vessels, increased through immaturity to peak during adulthood, decreasing with old age. Shy females had lower attraction to vessels and shy males remained at vessels longer, suggesting that bolder individuals may outcompete shyer ones, with positive consequences for mass gain. These results suggest that attraction to vessels is a learned process, leading to an increase with age, and is not the result of preferential attraction to new objects by juveniles. Overall, our findings have important conservation implications as a result of potential strong differential selection on the risk of bycatch for age classes, personality types, populations and species.

Abstract: Mercury (Hg) stable isotopes have been broadly used to investigate the sources, transformation and deposition of atmospheric Hg during the industrial era thanks to the multiple isotope signatures deriving from mass-dependent (represented by δ202Hg) and mass-independent fractionation (represented by ΔxxxHg) in the environment. Less is known about the impact of past climate change on atmospheric Hg deposition and cycling, and whether Hg isotopes covary with past climate. Here, we investigate Hg concentration and Hg isotope signatures in a 6600-year-old ombrotrophic peat record from Amsterdam Island (AMS, 37.8oS), and in modern AMS rainfall and gaseous elemental Hg (Hg0) samples. Results show that Holocene atmospheric Hg deposition and plant Hg uptake covary with dust deposition, and are both lower under a high humidity regime associated with enhanced Southern Westerly Winds. Modern AMS gaseous Hg0 and rainfall HgII isotope signatures are similar to those in the Northern Hemisphere (NH). Holocene peat Δ199Hg and Δ200Hg are significantly correlated (R2 = 0.67, P < 0.001, n = 58), consistently oscillating between the modern Hg0 and rainfall HgII end-members. Peat Δ200Hg and Δ199Hg provide evidence of plant uptake of Hg0 as the dominant pathway of Hg deposition to AMS peatland, with some exceptions during humid periods. In contrast to NH archives generally documenting a modern increase in Δ199Hg, recent peat layers (post-1900CE) from AMS show the lowest Δ199Hg in the peat profile (−0.42 ± 0.27 ‰, 1σ, n = 8). This likely reflects a significant change in the post-depositional process on deposited anthropogenic Hg in 20th century (i.e. dark abiotic reduction), enabling more negative Δ199Hg to be observed in AMS peat. We further find that the oscillations of Hg isotopes are consistent with established Holocene climate variability from dust proxies. We suggest peat Hg isotope records might be a valid rainfall indicator.

Abstract: En milieu océanique, la ressource est distribuée de façon hétérogène. De ce fait, les proies sont souvent regroupées en bancs (« patchs »). En 2014, le projet MyctO-3D-Map a permis de récolter au large de Kerguelen (Terres Australes et Antarctiques Françaises) des données simultanément sur la distribution des proies en milieu pélagique et sur le comportement de plongée de prédateurs marins. L’objectif de cette thèse était d’évaluer les stratégies de recherche alimentaire d’oiseaux plongeurs (manchots) en fonction de la distribution de leurs proies. À l’échelle de la plongée, les manchots royaux, Aptenodytes patagonicus, et les gorfous macaronis, Eudyptes chrysolophus, ajustent leur comportement en fonction de leur succès alimentaire lors de la plongée précédente. Lorsqu’ils rencontrent une zone favorable les manchots ont tendance à diminuer leur temps de surface et replonger à la même profondeur. Les manchots, comme de nombreux autres prédateurs plongeurs, effectuent des séquences de plongées répétées appelées « bouts ». Pendant les séries de prey capture attempt bouts (PCA bouts), où ces prédateurs réalisent des plongées successives de tentative de captures de proies, les gorfous macaroni et les manchots royaux modifient leur comportement de plongée en fonction de la longueur de la séquence. Plus la séquence est longue, plus l’activité de prospection est importante et plus les phases descendantes et ascendantes sont rapides. De plus, la densité de PCA bouts était similaire à la densité de patchs de poissons par km. Ces résultats suggèrent que l’unité de prospection alimentaire pour les manchots royaux serait le PCA bout. À l’échelle de la zone entière prospectée par les manchots royaux, ces prédateurs se dirigent vers une zone moins riche en biomasse mais où les patchs de poissons sont plus accessibles. Cette étude est l’une des rares ayant pu comparer des données acoustiques récoltées de façon simultanée aux données de recherche alimentaires chez des manchots pistés en mer. La distribution des patchs de poissons et plus encore leur accessibilité est donc un élément clé influençant le comportement de prospection alimentaire des prédateurs plongeurs, que ce soit à plus ou moins fine échelle.

Abstract: Cape Smith is an island near Akulivik, located on the northeastern coast of Hudson Bay (Canada). The Kangiakallak site (JeGn-2) is a large and mixed Palaeoeskimo and Thule/Inuit archaeological site located in a valley in the northeastern part of Cape Smith. The Dorset occupants built shallow semi-subterranean houses here on a plateau at the top of the valley. Later, the Thule/Inuit inhabitants constructed much deeper semi-subterranean sod houses (qarmait) on the edge of the beach ridges. The evidence shows that study region was a significant site for winter camps, likely because of its proximity to the partial polynya situated between the island and the mainland. The Kangiakallak site was among the first sites excavated by southern scientists in the 1940's and 1950's (Manning 1951) Our multidisciplinary research team conducted from 2011 excavations to answer some of the questions posed by the local Akulivik residents. The success of this project is largely due to community involvement and it shows the value of community-based research. The combination of paleoecological, paleogeographical and geoarchaeology data with archaeological and historical data made it possible to document the evolution of paleoenvironments and the habitability of the northeastern of Cape Smith, as well as the interactions between humans (Dorset, Thule/Inuit) and the environment in the context of climate change. In this presentation, we will provide a summary of the data from this interdisciplinary research.