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Brown Skuas (Stercorarius lonnbergi) are known to feed on other birds or eggs during the breeding season. In some cases, however, a few pairs monopolize a penguin colony, and the other skuas mainly forage in the sea. We installed automatic camera traps to monitor two groups of breeding Brown Skua pairs on King George Island: the nests of Group A were located near a Gentoo Penguin (Pygoscelis papua) colony, while those of Group B were relatively far away. From the resulting photographs, we were able to distinguish the food items that parents brought to the nest and could confirm the egg hatching date. Overall, 97.1% of the food items that group A brought to the nest were from the penguin colonies, while 94.1% of the prey items of group B were fish. Group A had a hatching date at least 8 days earlier than Group B. Our results show that a few Brown Skua pairs that bred near the penguin colony fed primarily on penguin nest contents such as eggs or chicks within their feeding territory and had earlier hatching dates. The Brown Skuas that nested close to penguin nests may have had advantages in foraging and breeding performance. [ABSTRACT FROM AUTHOR]

A long-term change of a subtidal macroalgal assemblage has been investigated in Maxwell Bay, King George Island (KGI) of the Antarctic coast by a revisit survey after 30 years. Field surveys were done by SCUBA diving at six sites in 2016–2018 to directly compare with the previous survey conducted in 1988–1993 at the same sites. The total number of macroalgal species was similar between the previous and the present survey, 25 and 27 species respectively. However, the macroalgal assemblage changed substantially with the average similarity of 48.2% between the two surveys. Also, the species-level abundance showed a high variability between surveys. On the other hand, over the 30 years interval there was little overall change at the between-site level hierarchical structure in the subtidal communities of Maxwell Bay. The sites near the penguin rookery consistently showed the highest biodiversity, indicating the importance of land-based nutrients input in Antarctic coastal habitats. A noticeable pattern change over 30 years was the increase of Desmarestia complex and Plocamium cartilagineum and the decrease of Himantothallus grandifolius. Both groups are still dominant, but the shift from Himantothallus to Desmarestia-Plocamium may reflects temperature rise on the Maxwell Bay coast compared to the past. [ABSTRACT FROM AUTHOR]

In many seabirds, individuals abstain from eating during the moult period. Penguins have an intense moult that lasts for weeks, during which they are confined to land. Despite the importance for survival, it is still unclear how the faecal microbiota of Antarctic penguins changes in response to the moult fast. Here, we investigated the faecal microbiota of chinstrap (Pygoscelis antarcticus) and gentoo penguins (Pygoscelis papua) on King George Island, Antarctica. The bacterial community compositions during the feeding and moulting stages were compared for both species using bacterial 16S rRNA gene amplicon on an Illumina MiSeq platform. Our results showed that the moult fast altered the bacterial community structures in both penguin species. Interestingly, the bacterial community composition shifted in the same direction in response to the moult fast but formed two distinct clusters that were specific to each penguin species. A significant increase in bacterial diversity was observed in gentoo penguins, whereas no such change was observed for chinstrap penguins. By analysing the contribution of the ecological processes that determine bacterial community assembly, we observed that processes regulating community turnover were considerably different between the feeding and moulting stages for each penguin. At the phylum level, the relative abundances of Fusobacteria, Firmicutes and Proteobacteria were dominant in chinstrap penguins, and no significant changes were detected in these phyla between the feeding and moulting periods. Our results suggest that moult fast-induced changes in the faecal microbiota occur in both species. [ABSTRACT FROM AUTHOR]

Temporal variability and the vertical shoreline profile of an intertidal macroalgal assemblage were examined on the coast of Barton Peninsula, Maxwell Bay, King George Island, Antarctica. Sampling was performed during the three austral summer seasons from November 2016 to January 2019. The sampling interval for the summer shift was 1–2 months. Eighteen algal species were identified, with 75% relative coverage of the predominant red alga Iridaea cordata and endemic brown alga Phaeurus antarcticus. Temporal variation in the macroalgal assemblage showed 78.35% similarity between one month and 64.61% similarity between two months. Contour plots for visualizing macroalgal distribution were first attempted in this study, and compared to general distribution of tables and diagrams that were discontinuously expressed. The coastscape was expressed more quantitatively and continuously, and was also useful for explaining temporal changes such as summer abundance can be described as a shift from I. cordata to P. antarcticus. In addition, in terms of species composition, this study area corresponds to the middle to lower intertidal zone and shows the highest species diversity in King George Island, so it is expected to provide important information for the researches in Antarctic intertidal zones. [Display omitted] • Seaweed abundance hotspot was found in King George Island. • Temporal variability in macroalgal assemblage was relatively high in Antarctica. • Contour plots intuitively represent vertical distribution of macroalgal assemblage. • Iridaea cordata and Phaeurus antarcticus mainly covered Antarctic intertidal zone. • Abundance shift from Iridaea to Phaeurus during summer. [ABSTRACT FROM AUTHOR]

Many marine birds dive to catch prey in water. The gentoo penguin (Pygoscelis papua), a specialized diving seabird that preys on krill and fish, is distributed from the sub-Antarctic islands to Antarctic regions. Here, we observed the diving behavior of breeding gentoo penguins on King George Island, South Shetland Islands, Antarctica. Using a time–depth recorder, we collected diving depths every second from seven gentoo breeders for 5–21 days during the chick-rearing period and analyzed their diving characteristics. Most dives occurred in shallow water, although the dive efficiency (=bottom duration time/[dive duration + post-dive surface time]) was highest at depths of 30–35 m and decreased as the penguins dove deeper. Gentoo penguins did not dive more frequently during the day than at night, but during nighttime, most dives occurred in shallow water (<20 m) and the dive efficiency was also higher at this time. As penguins repeated their foraging trips, the number of dives, depth of dives, and trip duration did not change significantly. Our results suggest that the diel dive patterns of gentoo penguins might be related to the vertical migration of krill (upward to the surface at night). In addition, we observed that gentoo penguins could perform active diving behavior even at night, possibly aided by civil twilight during the chick-rearing period in Antarctic regions. [ABSTRACT FROM AUTHOR]

The Cape petrel Daption capense, a seabird, is observed throughout the southern hemisphere including the Antarctic region. Herein, we report the complete mitogenome of Cape petrel with the GenBank accession number MH924023 to elucidate the genetic characteristics of this genus. The mitogenome is 17,312 bp long and comprises 13 protein-coding genes (PCGs), two rRNA genes, and 22 tRNA genes. The overall base composition of the 13 PCGs is as follows: A (31.1%), C (30.3%), T (25.4%), and G (13.2%), with a GC content of 43.5%. The results provide useful information for further genetic studies in Procellariiformes. [ABSTRACT FROM AUTHOR]

Simple Summary: Under limited resources, different species may coexist by segregating their food items and foraging time, but neighboring colonies within the same species may have highly overlapping foraging habits. Thus, it is hypothesized that intra-specific competition is more intense than the inter-specific competition. To test this hypothesis, we chose sympatrically breeding Chinstrap and Gentoo penguins at two neighboring colonies and tracked their foraging space and dive depths during chick-rearing. Here we report that there was a larger overlap in the foraging space between the two species than within each species, whereas there was lower inter-specific isotopic niche overlap than intra-specific isotopic niche overlap. Despite the low intra-specific spatial overlap, diets of conspecifics remained similar, resulting in the higher isotopic niche overlaps. Our results suggest that intra-specific competition is higher than inter-specific competition due to a lack of niche partitioning. Theory predicts that sympatric predators compete for food under conditions of limited resources. Competition would occur even within the same species, between neighboring populations, because of overlapping foraging habits. Thus, neighboring populations of the same species are hypothesized to face strong competition. To test the hypothesis that intra-specific competition is more intense than inter-specific competition owing to a lack of niche partitioning, we estimated the foraging area and diving depths of two colonial seabird species at two neighboring colonies. Using GPS and time-depth recorders, we tracked foraging space use of sympatric breeding Chinstrap and Gentoo penguins at Ardley Island (AI) and Narębski Point (NP) at King George Island, Antarctica. GPS tracks showed that there was a larger overlap in the foraging areas between the two species than within each species. In dive parameters, Gentoo penguins performed deeper and longer dives than Chinstrap penguins at the same colonies. At the colony level, Gentoo penguins from NP undertook deeper and longer dives than those at AI, whereas Chinstrap penguins did not show such intra-specific differences in dives. Stable isotope analysis of δ13C and δ15N isotopes in blood demonstrated both inter- and intra-specific differences. Both species of penguin at AI exhibited higher δ13C and δ15N values than those at NP, and in both locations, Gentoo penguins had higher δ13C and lower δ15N values than Chinstrap penguins. Isotopic niches showed that there were lower inter-specific overlaps than intra-specific overlaps. This suggests that, despite the low intra-specific spatial overlap, diets of conspecifics from different colonies remained more similar, resulting in the higher isotopic niche overlaps. Collectively, our results support the hypothesis that intra-specific competition is higher than inter-specific competition, leading to spatial segregation of the neighboring populations of the same species. [ABSTRACT FROM AUTHOR]

Ecological macroalgal succession in glacier-free areas has remained at the pioneer seral stage despite six decades of glacial retreat at Marian Cove, King George Island, Antarctica. With the rapid melting of glaciers in the West Antarctic Peninsula owing to global warming, a massive amount of meltwater is flowing into the coast, creating marine environmental gradients such as turbidity, water temperature, and salinity. This study examined the spatial and vertical distributions (up to a depth of 25 m) of macroalgal assemblages from nine sites in Maxwell Bay and Marian Cove. The macroalgal assemblages were analyzed for six sites located 0.2, 0.8, 1.2, 2.2, 3.6, and 4.1 km away from the glacier, including three sites where the glacial retreat history of Marian Cove could be estimated. To investigate the effects of meltwater, differences in the coastal environment were analyzed based on data collected from five stations located 0.4, 0.9, 3.0, 4.0, and 5.0 km away from the glacier. The macroalgal assemblages and marine environment were divided into two groups—inside and outside the cove—based on the region 2–3 km away from the glacier, which has been ice-free since 1956 and shows significant differences. In the three sites near the glacier front, Palmaria decipiens was dominant, and three to four species were distributed, whereas in the two sites outside the cove, nine and 14 species appeared, respectively, similar to the assemblage of the other three sites in Maxwell Bay. Palmaria decipiens , a representative opportunistic pioneer species in Antarctica, is dominant because of its physiological adaptation despite the high turbidity and low water temperature of the glacier front. This study shows that macroalgal assemblages in Antarctic fjord-like coves respond to glacial retreat and are valuable in understanding the macroalgal succession in Antarctica. • Macroalgal succession in Marian Cove is slower than the rate of glacial retreat. • Provides a snapshot of Antarctic summer macroalgal assemblages. • Palmaria decipiens , red algae, thrives in harsh Antarctic glacier front. • Light availability is crucial for their development. • Contour plots provide an intuitive visualization of vertical macroalgal distribution. [ABSTRACT FROM AUTHOR]

Abstract: δ13C and δ15N of the Antarctic limpet Nacella concinna tissues and their potential food sources were used to determine their dietary origins and their movements between diverse habitats of intertidal and subtidal rocky shores and tide pools of Marian Cove, King George Island, Antarctica in the austral summer. δ13C and δ15N of the organic matter sources of epilithic microalgae, macroalgae and suspended particulate organic matter (SPOM) were readily distinguishable to discern their relative contribution to the limpet diets, with the most depleted values being found in SPOM and the most enriched in macroalgae. The limpets exhibited a spatial trend in distribution due to their seasonal migration, with smaller individuals in the subtidal zone compared with larger ones on the intertidal sites. The limpet isotopes had relatively broad ranges of δ13C and δ15N (−26.6 to −12.8‰ and 2.6–7.1‰, respectively), suggesting a dietary shift between habitats as well as size classes. The stable isotope ratios for each habitat seem likely to reflect the differing availabilities of the three potential food sources. Isotope mixing model results indicate a spatial shift in dietary mixture between habitats as well as limpet size classes. Epilithic microalgae and phytoplankton made great contributions to the diet of the subtidal limpets. Together with epilithic microalgae, macroalgae were significant contributors to the intertidal limpets where macroalgae were abundant. A higher contribution of macroalgae to the limpet diets was found in the tide pools. In contrast, while phytoplankton was an important food source for the limpet spat, a great dietary dependence on epilithic microalgae was found in the small-size limpets from the lower intertidal zone. Our results suggest that limpet grazing can determine microalgal and/or macroalgal abundance and coverage on the Antarctic rocky-shore ecosystem, and trophic structure of benthic food web can change along environmental gradients even at spatial scales of tens or hundreds of metres in the Antarctic. [Copyright &y& Elsevier]

Drastic sea ice retreats in the Antarctic Peninsula, and the consequent environmental changes have brought about the consequences of biological adaptation and food competition. The isotopic niche is reflected by the ecological position and functional role of a species, which can be altered depending on these environmental changes. We assessed the isotopic niche and trophic positions (TP) of 3 seabirds on the Barton Peninsula, King George Island, Antarctica, to understand ecological interaction among the species. The average TP of Antarctic krill (Euphausia superba) (hereafter "krill") (2.6 ± 0.1) was estimated by using the compiled published data of the compound-specific nitrogen isotope ratio of glutamic acid and phenylalanine in the Southern Ocean, and TP values of the seabirds based on that of krill to be reliable according to ecological knowledge. Our results on the overlap of the isotopic niches of seabirds suggests potential diet competition among the consumers, such as the brown skua (Stercorarius antarcticus) and south polar skua (Stercorarius maccormicki), whereas the distinct and broad isotopic niche width of kelp gulls (Larus dominicanus) suggesting that their adaptation through generalization was related to their extended habitat and various food sources. Our research indicates that isotopic niche of seabirds reflects their survival strategy for food competition. Consequently, these seabirds can be easily influenced by alternative food sources, including terrestrial and human-derived sources, by rapid environmental changes, indicating that they are valuable as key environmental species and require long-term monitoring in the Antarctic Peninsula. • Isotopic niche and trophic positions of 3 seabirds on the Barton Peninsula were investigated. • The estimated trophic position from stable isotope agree with ecological knowledge. • Isotopic niches of seabirds represent their adaptation to the environment through competition and segregation. • Therefore, long-term monitoring of the niche shift of seabirds in response to environmental changes is required. [ABSTRACT FROM AUTHOR]

The occurrence and bioaccumulation of new and legacy persistent organic pollutants (POPs), organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), polychlorinated naphthalenes (PCNs), hexabromocyclododecanes (HBCDs), and Dechlorane Plus (DPs) and their related compounds (Dechloranes) in an ecosystem on King George Island, Antarctica are investigated. The new and legacy POPs were widely detected in the animal samples collected from Antarctica, which included Limpet, Antarctic cod, Amphipods, Antarctic icefish, Gentoo and Chinstrap penguins, Kelp gull, and South polar skua. The trophic magnification factors indicated that the levels of PCNs and HBCDs, as well as the legacy POPs, were magnified through the food web, whereas DPs might be diluted through the trophic levels contradicting the classification of Dechloranes as POPs. This is one of the first extensive surveys on PCNs, HBCDs, and Dechloranes, which provides unique information on the distribution and trophic biomagnification potential of the new and legacy POPs in the Antarctic region. ga1 • PCNs, HBCDs, and dechloranes are widespread in the Antarctic ecosystem. • PCNs and HBCDs are biomagnified through the trophic levels. • Dechloranes have TMF below 1, contradicting classification of dechloranes as POPs. [ABSTRACT FROM AUTHOR]