Abstract: We present ground- and space-based photometric observations of TOI-270 (L231-32), a system of three transiting planets consisting of one super-Earth and two sub-Neptunes discovered by TESS around a bright (K-mag = 8.25) M3V dwarf. The planets orbit near low-order mean-motion resonances (5:3 and 2:1) and are thus expected to exhibit large transit timing variations (TTVs). Following an extensive observing campaign using eight different observatories between 2018 and 2020, we now report a clear detection of TTVs for planets c and d, with amplitudes of ∼10 min and a super-period of ∼3 yr, as well as significantly refined estimates of the radii and mean orbital periods of all three planets. Dynamical modelling of the TTVs alone puts strong constraints on the mass ratio of planets c and d and on their eccentricities. When incorporating recently published constraints from radial velocity observations, we obtain masses of $M{\mathrm{b}}=1.48\pm 0.18\, M\oplus$, $M{\mathrm{c}}=6.20\pm 0.31\, M\oplus$, and $M{\mathrm{d}}=4.20\pm 0.16\, M\oplus$ for planets b, c, and d, respectively. We also detect small but significant eccentricities for all three planets : eb = 0.0167 ± 0.0084, ec = 0.0044 ± 0.0006, and ed = 0.0066 ± 0.0020. Our findings imply an Earth-like rocky composition for the inner planet, and Earth-like cores with an additional He/H2O atmosphere for the outer two. TOI-270 is now one of the best constrained systems of small transiting planets, and it remains an excellent target for atmospheric characterization.

Abstract: Qikirtajuaq is a long island facing the Inuit village of Akulivik on the northeastern coast of Hudson Bay (Canada) that is rich in archaeological sites. Kangiakallak-1 (JeGn-2), one of the main sites on this island, is a large multicomponent site that includes Dorset and Thule Inuit winter houses. This study documents the dynamics of palaeoenvironmental conditions in the successive occupations of the Kangiakallak-1 settlement based on plant macrofossils, pollen and non-pollen palynomorph analyses and archaeological research. The data indicate that Dorset inhabitants constructed their dwelling at about 772 cal. a BP. The site was reused by the Thule Inuit a few decades later, starting at about 671 cal. a BP. Thus, Kangiakallak-1 is one of the few sites, at least in Nunavik (northern Quebec, Canada), that were rapidly reoccupied by the Thule Inuit after the departure of the Dorset inhabitants, which indicates a possible overlap between the two cultures in the Akulivik region. The palaeoecological data show that both Dorset and Thule inhabitants left clear footprints at the local scale in the form of several nitrophilous species that became established in and near the houses and persisted over a long period. The deposition of domestic waste (including bone fragments, skin, burnt fat and charcoal fragments) inside the subterranean dwellings fertilized the soil and led to the growth of unique nitrophilous plants. These changes transformed the houses into exceptional floristic refuges.

Abstract: Feral cats (Felis catus) are a potential threat for several seabird species including medium sized albatrosses, but studies documenting predation behavior, demographic impacts and effects of predator control are scarce. Here, we present data on feral cat predation behavior on one of the world’s largest seabirds, the wandering albatross (Diomedea exulans) at Kerguelen Island, and show how it affects breeding success and rate of population growth. We assess the effect of a feral cat control experiment on breeding success and population viability. Using 32 camera traps we monitored 25 nests of albatross and detected 295 events showing a potential predator. Of these, 75.2% and 24.8% involved feral cats and giant petrels, respectively. Giant petrels were never implicated in direct predation. We recorded 17 attacks of feral cats on 13 albatross chicks. Attacks lasted in average 52.1 ± 72.9 min, and resulted in the death of 10 of the 13 (76.9%) monitored chicks. Breeding success where attacks were recorded was low (12%) compared to areas with no attack (86%). Mean breeding success during 3 years before cat control was 26% and increased to 80% during the 3 years following the experiment. According to predation scenarios, population modelling showed that the albatross population would decline by 2.7–4.5% per year without cat control. Following cat control the population would increase at 1.8% per year. Our results demonstrate that feral cats predate and have negative impacts on breeding success and population growth rate of wandering albatrosses at Kerguelen Island. We provide recommendations on feral cat control and eradication to mitigate the risk of population decline or local extinction of large albatrosses.

Abstract: Albatrosses attend fishing boats to feed on fishing discards but are often at risk of accidental bycatch. To examine whether populations (same species) and sexes differ in their overlap with fisheries due to differences in habitat use, we combined the use of recently developed loggers equipped with GPS and boat radar detectors with Automatic Identification System (AIS) data. Our study indicates that incubating wandering albatrosses Diomedea exulans from Crozet and Kerguelen foraged in different habitats although the duration of trips was similar. Both female and male Kerguelen birds took advantage of the large and productive surrounding shelf, whereas Crozet birds used the small shelf around the islands to a lesser extent. In Crozet, there was segregation between males and females, the latter favouring deeper and warmer waters. The 2 strategies of habitat use led to different overlap and attraction to boats, with Kerguelen birds encountering and attending boats for longer and at closer proximity to the colony than Crozet birds. Crozet females encountered boats at greater distances from the colony than males. Because of their different habitat use and foraging outside exclusive economic zones (EEZ) and further from the colony, Crozet birds attended more non-declared boats (without AIS) than Kerguelen birds. Albatrosses were more attracted by fisheries than cargo vessels and were especially attracted by fishing discards that led them to attend vessels for longer periods for both sexes and populations. The differences found between populations and individuals in terms of habitat specialization and encounter rate of fisheries should be considered for future assessments of risk of bycatch.

Abstract: In vivo and in vitro evidence for detoxification of methylmercury (MeHg) as insoluble mercury selenide (HgSe) underlies the central paradigm that mercury exposure is not or little hazardous when tissue Se is in molar excess (Se:Hg > 1). However, this hypothesis overlooks the binding of Hg to selenoproteins, which lowers the amount of bioavailable Se that acts as a detoxification reservoir for MeHg, thereby underestimating the toxicity of mercury. This question was addressed by determining the chemical forms of Hg in various tissues of giant petrels Macronectes spp. using a combination of high energy-resolution X-ray absorption near edge structure and extended X-ray absorption fine structure spectroscopy, and transmission electron microscopy coupled to elemental mapping. Three main Hg species were identified, a MeHg-cysteinate complex, a four-coordinate selenocysteinate complex (Hg(Sec)4), and a HgSe precipitate, together with a minor dicysteinate complex Hg(Cys)2. The amount of HgSe decreases in the order liver > kidneys > brain = muscle, and the amount of Hg(Sec)4 in the order muscle > kidneys > brain > liver. On the basis of biochemical considerations and structural modeling, we hypothesize that Hg(Sec)4 is bound to the carboxy-terminus domain of selenoprotein P (SelP) which contains 12 Sec residues. Structural flexibility allows SelP to form multinuclear Hgx(Se,Sec)y complexes, which can be biomineralized to HgSe by protein self-assembly. Because Hg(Sec)4 has a Se:Hg molar ratio of 4:1, this species severely depletes the stock of bioavailable Se for selenoprotein synthesis and activity to one μg Se/g dry wet in the muscle of several birds. This concentration is still relatively high because selenium is naturally abundant in seawater, therefore it probably does not fall below the metabolic need for essential selenium. However, this study shows that this may not be the case for terrestrial animals, and that muscle may be the first tissue potentially injured by Hg toxicity.