In the krill-based ecosystem of the Antarctic, fluctuations in the distribution and abundance of Euphausia superba may have strong impacts on predator populations; thus, it is crucial to observe the feeding ecology of Antarctic predators, especially in the light of climate change and increasing human pressure. We determined the composition of euphausiid species in diet samples collected from Adélie (Pygoscelis adeliae), chinstrap (Pygoscelis antarcticus) and gentoo (Pygoscelis papua) penguins on King George Island (South Shetlands Islands) during a breeding season. For all three penguin species, euphausiids (mainly E. superba) represented almost the entirety of researched stomach samples (i.e. 99.9% in the case of Adélie and chinstrap penguins), while gentoo penguins also proved to feed on fish (99.4% krill; 0.5% fish). Analysed material differed in the size of eaten E. superba specimens, with the smallest crustaceans consumed by Adélie penguins. Furthermore, we found differences in the ratio of consumed krill and krill size. Such disparities may be a result of sex-based differences and slight differences in feeding areas between the birds. Additionally, we noted some fragments of plastic debris in the investigated penguin diet samples.

In recent years, functional changes in Southern Ocean are becoming more noticeable, due to climate change and increasing human impacts, including a growing fishery that is concentrating in the Antarctic Peninsula (AP) region. Antarctic krill Euphausia superba is often the primary prey species for animals such as Pygoscelis penguins, a sentinel species for ecosystem monitoring and management. During the last two decades in the AP gentoo penguin numbers (Pygoscelis papua) have increased and their range has shifted southward, in contrast to the decline in numbers of Adélie (P. adeliae) and chinstrap (P. antarcticus) penguins. Given divergent population trends, the goal of this study was to examine differences in their diet, and size structure of Antarctic krill recovered from penguin diet samples. The study is based on diet samples collected during the austral summers on King George Island (South Shetland Islands) where P. adeliae, P. antarcticus, and P. papua breed in mixed colonies. Results indicate that the penguins consumed krill of similar sizes during the breeding period. In contrast to prior diet studies, we found higher proportions of krill in the gentoo diet and changes in the percentage of krill in the diet relative obtained during 1970s. The similarity in diets among all three species suggests that the availability prey items (e. g., fishes) may be changing and driving higher dietary overlap. Moreover, we also check differences in krill length among penguin individuals and we did not find any statistically significant differences. We also found plastic debris in penguin stomachs during both summers.

Changes in macrobenthic and pelagic communities in the postglacial, partially isolated, lagoon Herve Cove in Admiralty Bay, King George Island, were investigated 15 years after the first comprehensive studies had been conducted in this region. The bottom area of the cove has enlarged from approximately 12 ha to 19 ha after the retreat of the Dera Icefall. Based on a photographic survey of the benthos and taxonomic composition of zooplankton, ecological succession and the colonization of new species have been observed. Several new species occur such as gastropods, seastars, sea urchins and isopods, and their presence in different parts of the cove, as well as breeding aggregations suggests that they reproduce there. The influence of glacial streams is notable in bottom assemblages. We propose that Herve Cove is a good research area for studies on ecological succession in newly opened areas. The colonization of this lagoon has been recognized to be in its developing stage, and research should be continued.

Appendicularians are one of the most common animals found within zooplankton assemblages. They play a very important role as filter feeders but are, unfortunately, inconsistently reported in the Antarctic literature. The present paper attempts to describe the zonal diversity of appendicularians and the main environmental factors influencing their communities in the Drake Passage. Samples were collected during Antarctic summer in 2009–2010. A total of eight species of larvaceans were identified. Fritillaria borealis was the species found in the highest numbers in almost the entire studied area, and was observed at all sampling stations. The distributions of other taxa were limited to specific hydrological zones and hydrological conditions. F. fraudax and Oikopleura gaussica were typical of the areas between the Polar Front and the Subantarctic Front zones, and their distributions were significantly correlated with temperature and salinity, likely making them good indicator species. The F. fusiformis distribution was strictly related to South American waters. In summary, temperature was the strongest environmental factor influencing the larvacean community structure in the Drake Passage, and we also found that testing environmental factors on larvaceans as a whole group did not give entirely reliable results.

Based on some coincident morphological characters and distribution, it was believed for a long time thatMica miculawas the post-larval stage of a species ofBargmannia, a genus having a very wide geographic distribution. Recent studies, however, have shown that it is much more likely to be the post-larval form of the physonectPyrostephos vanhoeffeni, which is very common in both Antarctic and sub-Antarctic waters. Until now, molecular evidence to support this theory has been lacking. In the present study 34 nectophores ofP. vanhoeffeniand four colonies ofM. miculacollected from three areas in the Southern Ocean were analysed for the 16S rRNA gene. Five haplotypes were identified, which formed two clearly distinct lineages. Three haplotypes were found exclusively in Admiralty Bay and were shared between individuals of both studied taxa, confirming thatM. miculais indeed the post-larval stage ofP. vanhoeffeni. Two additional haplotypes were found in one open ocean locality and in Admiralty Bay.