Retreating Shorelines as an Emerging Threat to Adélie Penguins on Inexpressible Island

Long-term observation of penguin abundance and distribution may warn of changes in the Antarctic marine ecosystem and provide support for penguin conservation. We conducted an unmanned aerial vehicle (UAV) survey of the Adélie penguin (Pygoscelis adeliae) colony on Inexpressible Island and obtained aerial images with a resolution of 0.07 m in 2018. We estimated penguin abundance and identified the spatial extent of the penguin colony. A total of 24,497 breeding pairs were found on Inexpressible Island within a colony area of 57,507 m2. Based on historical images, the colony area expanded by 30,613 m2 and abundance increased by 4063 pairs between 1983 and 2012. Between 2012 and 2018 penguin abundance further increased by 3314 pairs, although the colony area decreased by 1903 m2. In general, Adélie penguins bred on Inexpressible Island at an elevation <20 m, and >55% of penguins had territories within 150 m of the shoreline. This suggests that penguins prefer to breed in areas with a low elevation and close to the shoreline. We observed a retreat of the shoreline on Inexpressible Island between 1983 and 2018, especially along the northern coast, which may have played a key role in the expansion of the penguin colony on the northern coast. In sum, it appears that retreating shorelines reshaped penguin distribution on the island and may be an emerging risk factor for penguins. These results highlight the importance of remote sensing techniques for monitoring changes in the Antarctic marine ecosystem and providing reliable data for Antarctic penguin conservation.

Regional Differences in the Diets of Adélie and Emperor Penguins in the Ross Sea, Antarctica

To identify the dietary composition and characteristics of both Adélie (Pygoscelis adeliae) and Emperor (Aptenodytes forsteri) penguins at four breeding sites, we performed stable carbon (δ13C) and nitrogen (δ15N) isotope analysis of down samples taken from penguin chicks. Adélie Penguin chicks at Cape Hallett mostly fed on Antarctic krill (Euphausia superba; 65.5 ± 3.5%), a reflection of the prevalence of that species near Cape Hallett, and no significant differences were noted between 2017 and 2018. However, Adélie Penguin chicks at Inexpressible Island, located near Terra Nova Bay, fed on both Antarctic silverfish (Pleuragramma antarctica; 42.5%) and ice krill (Euphausia crystallorophias; 47%), reflecting the high biomass observed in Terra Nova Bay. Meanwhile, no significant difference was noted between the two breeding sites of the Emperor Penguin. Emperor Penguin chicks predominantly fed on Antarctic silverfish (74.5 ± 2.1%) at both breeding sites (Cape Washington and Coulman Island), suggesting that diet preference represents the main factor influencing Emperor Penguin foraging. In contrast, the diet of the Adélie Penguin reflects presumed regional differences in prey prevalence, as inferred from available survey data.

Seabirds of human settlements in Antarctica: A case study of the Mirny Station

Antarctica is free of urbanisation, however, 40 year-round and 32 seasonal Antarctic stations operate there. The effects of such human settlements on Antarctic wildlife are insufficiently studied. The main aim of this study was to determine the organization of the bird population of the Mirny Station. The birds were observed on the coast of the Davis Sea in the Mirny (East Antarctica) from January 8, 2012 to January 7, 2013 and from January 9, 2015 to January 9, 2016. The observations were carried out mainly on the Radio and Komsomolsky nunataks (an area of about 0.5 km). The duration of observations varied from 1 to 8 hours per day. From 1956 to 2016, 13 non-breeding bird species (orders Sphenisciformes, Procellariiformes, Charadriiformes) were recorded in the Mirny. The South polar skuas (Catharacta maccormicki) and Adélie penguins (Pygoscelis adeliae) form the basis of the bird population. South polar skuas are most frequently recorded at the station. Less common are Brown skuas (Catharacta antarctica lonnbergi) and Adélie penguins. Adélie penguins, Wilson's storm petrels (Oceanites oceanicus), South polar and Brown skuas are seasonal residents, the other species are visitors. Adélie penguins, Emperor (Aptenodytes forsteri), Macaroni (Eudyptes chrysolophus) and Chinstrap penguins (Pygoscelis antarctica), Wilson's storm petrels, South polar and Brown skuas interacted with the station environment, using it for comfortable behavior, feeding, molting, shelter from bad weather conditions, and possible breeding. South polar and Brown skuas tend to be attracted to the station, while other Antarctic bird species are indifferent to humans. Birds spend part of the annual cycle at the station or visit it with different frequency, but they cannot meet their ecological needs there all year round. The study improves our understanding of the regularities of the phenomenon of urbanization of the avifauna in the polar regions of the planet Earth.

Spatial and temporal diet variability of Adélie (Pygoscelis adeliae) and Emperor (Aptenodytes forsteri) Penguin: a multi tissue stable isotope analysis

The Ross Sea, Antarctica, supports large populations of Emperor Penguin (Aptenodytes forsteri) and Adélie Penguin (Pygoscelis adeliae), two key meso-predators that occupy high trophic levels. Despite these species are largely studied, little is known about their diet outside the breeding period. In the present study, we investigated the intra-annual diet of Adélie and Emperor Penguins belonging to five colonies in the Ross Sea through the stable isotope analysis of different tissues (feathers and shell membranes), synthetized in different seasons, and guano that indicates recent diet. Penguin samples and prey (krill and fish) were collected during the Antarctic spring–summer. δ13C and δ15N of tissues and guano indicate spatio-temporal variation in the penguin diet. The krill consumption by Adélie Penguins was lowest in winter except in the northernmost colony, where it was always very high. It peaked in spring and remained prevalent in summer. The greatest krill contribution to Emperor Penguin’s diet occurred in summer. The relative krill and fish consumption by both species changed in relation to the prey availability, which is influenced by seasonal sea ice dynamics, and according to the penguin life cycle phases. The results highlight a strong trophic plasticity in the Adélie Penguin, whose dietary variability has been already recognized, and in the Emperor Penguin, which had not previously reported. Our findings can help understand how these species might react to resource variation due to climate change or anthropogenic overexploitation. Furthermore, data provides useful basis for future comparisons in the Ross Sea MPA and for planning conservation actions.

Seabirds in Conditions of Local Chronic Oil Pollution, Davis Sea, Antarctica

Oil spills are rare in Antarctica. They threaten flying birds and penguins. This is the first report on the interactions of seabirds with oil in the area of the Mirny Station (East Antarctica). The purpose of the study is to determine the total number of seabird species interacting with oil in and around the Mirny Station, to assess the extent of pollution and to identify the most important sites of interactions. Oil pollution is found on the ground, on the continental ice and, on the seawater surface, both directly in the Mirny and beyond. Five species of seabirds were in contact with oil. Oil pollution threats have been identified for breeding and molting Adélie Penguins (Pygoscelis adeliae) and vagrant Macaroni Penguins (Eudyptes chrysolophus). Less affected by oil pollution during the breeding season were tube-nosed bird species and skuas. The most important places of interaction of seabirds with oil are at Cape Mabus, on the islands of Zykov, Tokarev, and Stroiteley. Evidence of long-term oil pollution of the environment is indicative of the chronic nature of the impacts on the coastal ecosystem.

Assessing Serratia spp. pathogenic potential from cryogenic habitats

The genus Serratia are opportunistic bacteria widely spread in natural environment. At the same time, this bacterial genus consists of the species associated with outbreaks of nosocomial infections. Serratia species are found in extreme habitats, but pathogenic potential of polyextremophilic strains in this genus remains unexplored. The aim of this study was to compare the genomes of two Serratia strains isolated in polar regions, primarily examining genetic factors of virulence and adaptation to cryogenic environment. During the 56th Russian Antarctic Expedition the Serratia liquefaciens 72 strain was isolated from a guano sample of the Adelie Penguin (Pygoscelis adeliae) colony on Tokarev Island (Haswell Archipelago, East Antarctica). The Serratia fonticola 5l strain was isolated from the frozen carcass of moose (Alces alces) fossils found on the Buor-Khaya Peninsula near the Laptev Sea coast (Yakutia Region, Russia). The whole-genome sequencing of such strains allowed to reveal genetic structures evidencing about their successful adaptation to low temperatures. Thus, it was found that both genomes contain genes encoding the main cold shock proteins, phylogenetically close to the corresponding genes in the hypobarotolerant Serratia liquefaciens strain ATCC 27592. Furthermore, both strains bear a cluster of tc-fABCD genes determining the bacterial adhesion to epithelial tissues, and the genes for RTX toxins — adhesins, crucial factors of biofilm formation in pathogenic Gram-negative bacteria. Experimental studies confirmed the ability of Serratia liquefaciens 72 and Serratia fonticola 5l to actively form biofilms in a wide temperature range (from 6°C to 37°C). The results obtained indicate that the examined genus Serratia strains isolated in Arctica and Antarctica exert overall similar adaptation strategies to polar climate, including the ability to produce pili, show active adhesion, and biofilm formation under low temperatures. Genetic adaptive factors may also act as pathogenicity factors allowing extremotolerant Serratia strains to exert traits of opportunistic and nosocomial pathogens and spread via chilled food-borne transmission. The wide use of food technologies, such as cooling and vacuum sealing, can potentially create a new ecological niche favourable for selection of psychrotolerant and hypobarotolerant pathogens. The data obtained allow to raise a question about necessity of further studies to monitor genetic diversity among psychrophilic hypobarotolerant microbial populations possessing pathogenic and epidemic potential.

Pitfalls and advances in morphometric sexing: insights from the Adélie penguin Pygoscelis adeliae

Sexing weakly/criptically dimorphic birds requires invasive techniques or molecular analysis. Alternatively, sexing can be based upon morphometric analysis, which remains invaluable in remote field conditions such as Polar regions. Nevertheless, discriminatory power may be affected by methodological issues hampering comparison between/within studies, e.g. considering alternative analytical techniques or measurements taken by different researchers. We investigated the sexing potential of bill length, bill depth and body mass in adult Adélie penguins Pygoscelis adeliae of known sex. We performed discriminant analysis on a large dataset of measurements (237 males; 264 females) taken from penguins marked between 1994 and 2001, at Edmonson Point (Ross Sea, Antarctica). In a second step, we accounted for measurements collected by different researchers through permuted discriminant analysis. We found moderate support for sex discrimination through bill measurements (77%). Considering body mass did not improve classification power substantially (78.2%), possibly because of confounding inter/intra-annual oscillations in body condition. Discriminant rate decreased when controlling the researcher effect (72.7% and 71.4%, respectively). Results were also confirmed by logistic (mixed) models. Simulations showed that reduction in sample size markedly increased uncertainty in classification power. Differences with previous studies achieving a slightly greater classification power for sexing Adélie penguins through morphometrics could be related to (i) our higher sample size and/or (ii) geographical, population-specific differences, e.g. lower degree of sexual dimorphism. Our work emphasises key-factors influencing performance of morphometric sexing in avian species, advocating population-specific validation with large sample size as well as the necessity to account for the researcher effect prior to apply morphometric sexing.