Increases in atmospheric CO2 have led to more CO2 entering the world’s oceans, decreasing the pH in a process called ’ocean acidification’. Low pH has been linked to impacts on macroalgal growth and stress, which can alter palatability to herbivores. Two common and ecologically important macroalgal species from the western Antarctic Peninsula, the unpalatable Desmarestia menziesii and the palatable Palmaria decipiens, were maintained under three pH treatments: ambient (pH 8.1), near future (7.7) and distant future (7.3) for 52 days and 18 days, respectively. Discs of P. decipiens or artificial foods containing extracts of D. menziesii from each treatment were presented to the amphipod Gondogeneia antarctica in feeding choice experiments. Additionally, G. antarctica exposed to the different treatments for 55 days were used in a feeding assay with untreated P. decipiens. For D. menziesii, extracts from the ambient treatment were eaten significantly more by weight than the other treatments. Similarly, P. decipiens discs from the ambient and pH 7.7 treatments were eaten more than those from the pH 7.3 treatment. There was no significant difference in the consumption by treated G. antarctica. These results suggest that ocean acidification may decrease the palatability of these macroalgae to consumers but not alter consumption by G. antarctica.

Sub-Antarctic marine life exhibits unique ecological traits and pronounced endemicity levels. Despite their ecological uniqueness and high conservation value, studies on sub-Antarctic benthic communities are scarce. Using underwater video imagery, we assessed the nearshore diversity and structure of faunal and algal communities of the Crozet archipelago along 12 scuba and remotely operated vehicle transects performed at Baie du Marin and Crique du Sphinx (Ile de la Possession). The influence of habitat types on species distribution was evaluated in relation to the setting up of submarine cables. A total of 51 faunal (mainly represented by Echinodermata and Porifera) and 14 algal (mainly represented by Rhodophyta) taxa were identified. The high habitat heterogeneity found in shallow waters (from 0 to 20 m depth) enhances the species richness and diversity, whereas deeper (> 20 m depth) areas were dominated by large sandy stretches and a lower diversity. Rocky habitats had the highest richness and diversity values, promoting local diversity. Submarine cables act as a hard substrate for species, whose suspended sections influence the composition and structure of benthic communities. This study improves our limited knowledge of benthic habitats and diversity from Crozet and constitutes a baseline for further monitoring of marine communities for conservation strategies related to this part of the French Southern Territories National Nature Reserve.

Recent studies have revealed significant hidden diversity and a high incidence of cryptic speciation in Antarctic marine gastropods. Originally, philinoid cephalaspideans in the Southern Ocean were classified within the genus Philine. However, molecular and morphological studies have shown that three genera encompass all known diversity instead. These are Antarctophiline, Waegelea and Spiraphiline, the first two belonging to the recently erected family Antarctophilinidae. In this study, 55 specimens were collected from the South Shetland Islands, across the South Atlantic Antarctic Ridge to Bouvet Island, and from the South Sandwich Islands and Bransfield Strait, between 134 and 4548 m depth. We conducted morpho-anatomical and phylogenetic analyses to describe two new Antarctophiline species: Antarctophiline abyssalis sp. nov. and Antarctophiline malaquiasi sp. nov. Molecular results support the validity of the two distinct species, consistent with observed morpho-anatomical differences in the digestive system (i.e. the shape of gizzard plates and salivary glands), shell shape and other external characters. Additionally, we evaluate the morphological affinities of the most common Antarctic species, Antarctophiline alata, throughout its distribution range. Overall biogeographical distributions are discussed in a systematic context. Our study is yet another example of how Antarctica keeps revealing itself as a cornerstone of gastropod diversity.

In the sub-Antarctic, where food webs are relatively simple and species richness is low, the introduction of predators can be devastating, as native prey may lack sufficient defences and native predators may be less competitive. Merizodus soledadinus Guerin-Meneville, 1930 is a predatory carabid beetle that has been introduced to two sub-Antarctic islands. This ground beetle is known to threaten native insect populations; however, the full extent of its impacts in its introduced ranges is unknown because of its poorly described dietary breadth. As invasive predator impacts depend strongly on their dietary preferences and behaviour, we performed experiments to study the responses of this beetle to olfactory cues and sub-Antarctic diet. We studied the responses of M. soledadinus to olfactory cues to understand whether this species relies on odour to locate prey or different habitats, but we found no significantly different responses to different stimuli. We found that M. soledadinus attacked and consumed mostly juvenile forms of invertebrates from diverse phylogenetic lineages, indicating that many native species may be at risk from this predator and that attack by multiple individuals increased their success with hunting difficult prey. Our findings reveal that M. soledadinus has a wide dietary breadth, which has probably contributed to its successful establishment in multiple novel communities. We discuss the implications of our results for the ecology and conservation of terrestrial macroinvertebrate communities in its colonized range, where limited options exist to prevent further spread of this invader.

The Antarctic active volcano Deception Island has been the subject of extensive geological, geophysical and geomorphological research, including studies on its volcanic history. Since the initial geoscientific research, many authors have included lineament traces (in general considered as faults) in the maps, schemes and figures accompanying their publications. In the last 3 decades, several papers have contributed to improving our understanding of the volcano’s structure. In some cases, the fracture network was identified, measured and analysed and general models of the island’s structure were developed. However, the various authors have not always used consistent methodologies for lineament mapping, presenting significant disparities in the obtained results. This paper analyses previously interpreted lineaments and integrates existing geophysical, geological and morphostructural evidence, along with original field data, to establish a morphostructural model through a coherence and uncertainty analysis. The lineaments determined on Deception Island exhibit three preferred directions: NE-SW, ESE-WSW and SSE-NNW. However, the fractures measured in the field generally show a radial distribution, although there are two preferred directions: NNE-SSW and SE-NW. A synthetic map of Deception Island’s lineaments is presented, indicating which are the lineaments that should be considered tectonic-volcanic fractures among the other existing lineaments.